CA1150536A - Annular hole cutter - Google Patents
Annular hole cutterInfo
- Publication number
- CA1150536A CA1150536A CA000375298A CA375298A CA1150536A CA 1150536 A CA1150536 A CA 1150536A CA 000375298 A CA000375298 A CA 000375298A CA 375298 A CA375298 A CA 375298A CA 1150536 A CA1150536 A CA 1150536A
- Authority
- CA
- Canada
- Prior art keywords
- cutter
- flute
- radially
- called
- cutting edges
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B51/00—Tools for drilling machines
- B23B51/04—Drills for trepanning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B2251/00—Details of tools for drilling machines
- B23B2251/14—Configuration of the cutting part, i.e. the main cutting edges
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B2251/00—Details of tools for drilling machines
- B23B2251/40—Flutes, i.e. chip conveying grooves
- B23B2251/408—Spiral grooves
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Drilling Tools (AREA)
- Milling Processes (AREA)
- Crushing And Pulverization Processes (AREA)
- Auxiliary Devices For Machine Tools (AREA)
- Polishing Bodies And Polishing Tools (AREA)
Abstract
ANNULAR HOLE CUTTER
Abstract of the Disclosure An annular hole cutter wherein each tooth is formed with at least three cutting edges, each of which is designed to cut a separate chip. The two radially innermost cutting edges are formed on the portion of each tooth which corresponds to the thickness of the web between successive teeth. The web has a thickness which is preferably greater than the radial depth of the flute between successive teeth.
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Abstract of the Disclosure An annular hole cutter wherein each tooth is formed with at least three cutting edges, each of which is designed to cut a separate chip. The two radially innermost cutting edges are formed on the portion of each tooth which corresponds to the thickness of the web between successive teeth. The web has a thickness which is preferably greater than the radial depth of the flute between successive teeth.
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Description
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This invention relates to an annular hole cutter.
In my prior U.S. Reissue Patent No. 28,416 there is disclosed an annular cutter having a plurality of teeth spaced around the leading (lower) end of the cutter. Each tooth is provided with a plurality of circumferentially staggered cutting edges. The cutting edges are designed so that each will cut its own chip.
- The ~adially inr3ermost cutting edge exte~ds radially across a shallow gullet formed in the web between suc-cessive teeth and the outermost cutting edge extends radially across an outer flute which extends spirally upwardly of the cutter between successive teeth. In accordance with the teaching of my prior patent, the flute has a radial depth equal to about one-half the thickness of the annular wall of the cutter and the web has a thickness equal to about one-half the thick-ness of the annular wall. Consequently, the radially inner cutting edge of each tooth has a radial extent also equal to about one~half the wall thickness of the cutter. Thus, the flute has a radial depth which is sufficient to accommo~ate the discharge of chips cut by both cutting edges.
The prior patent referred ko also suggests that, if it is desired to provide three circumferen-tially staggered cutting edges on each tooth so that each tooth cuts three chips instead of two, the radial depth of the flute and the thickness of the web are maintained the same as for the two step tooth cutter and the portion of the cutter wall which corresponds to the depth of the flute is formed into two circumferen-tially staggered cutting edges Pather than a single cutting edge. The radially outermost cutting edge is defined by an outer gullet which has a relatively short axial dimension and opens into the ~lute. ~owever, the flute still has a radial dimension equal approximately to one-half the wall thickness of the cutter so that it can readily accommodate the chip cut by the radially innermost cutting edge.
While the cutter disclosed in my prior patent produces cutting action which is far superior to annular cutters previously used, under some conditions of feeds and speeds there is a tendency for the chips to become packed in the inner gullet and the flute. When this occurs the cutting action is much slower and a tapered - . oversized hole with a coarser finish is produced. In addition, the life of the cutting edge is substantially sho~tened. I have determined that the most practical $~6 way of overcoming this problem of chip packing in the flute of an annular cutter is to provide a cutter design which will produce thin, narrow chips.
Normally as soon as a chip is cut it begins to curl into a spiral. The volume and stiffness of a spiral chip is determined by its width and thickness. If a chip is wide it does not bend readily and occupies a relative-ly large volume. The net result of a large volume spiral chip is that less chip ma~erial can flow upwardly through the passageway defined by a flute in a given amount of time. However, if a chip is narrow it bends easily when it encounters an obstruction, such as the wall of a flute or hole, and requires far less flute depth as it moves upwardly through a flute-. A narrow chip can also be easily distorted beyond its elastic limit and thus frac-tures easily into smaller fragments. In addition, a narrow chip forms a radially compressible, spring-like spiral helix which is adapted to intertwine with other~
as it moves up a spiral flute. When such intertwined spiral chips engage the wall of the hole being formed by the cutter, the resultiny friction tends to resist their further rotation with the cutter which causes them to be forcibly cammed upwardly by the trailing side wall of the helical flute without clogying the flute. Thus it follows that a flute can be reduced in cross sectio~al L. ~
area as the width of the chip is reduced. ~t also follows that with a cutter side wall of a given thickness, as the size of the flute is reduced, the strength of the cutter is increased since the web between successive teeth will be thickerO A thicker web provides greater rigidity, thus producing a more accurate hole with a better finish. With increased cutter strength a thicker chip may be cut and/or a greater number of teeth may be used; thus a faster cutting action is also obtained.
The primary object of this invention is to pro-vide an annular cutter which cuts more efficiently, more rapidly, and more accurately; produces a better finish;
has a longer life and which, at the same time, has a greater resistance to breakage than an equivalent size cutter of the prior art.
A more specific object of this invention is to provide a fluted annular cutter wherein each tooth has a plurality of at least three cutting edges thereon, each of which preferably has a radial dimension substantially less than one-half the wall thickness of the cutter so that the radial dimension of the flute can be as small as about one-third the wall thickness of the cutter and still sufficiently deep to freely accommodate the chip cut by the widest cutting edge~
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Another object of this invention is to provide an annular hole cutter which is more efficient and has a higher strength than prior art cutters of the same size.
This is obtained by forming each tooth of the cutter with at least three cutting edges, each of which is adapted to cut a separate chip and two of which are formed on that portion of the cutter side wall located radially inwardly of the flute, that is, in the web section between suc-cessive teeth.
Another object of the invention is to provide an annular cutter which is admirably adapted to be form-ed as two axially adjacent sections telescopically join-ed together so that ~he leading end portion of the cutter on which the teeth are formed can be made of a relatively expensive cutting tool ~laterial, such as high speed steel, and the body portion of the cutter made of a less expensive material, such as a heat-treated, relatively low alloy steel.
Another object of the invention is to provide a design for an annular hole cutter thak enables the manufacture of cutters of small diameter and with sub-stantially less tendency to develop hairline cracks when the flutes are ground or heat treated.
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A further object of the invention is to provide a design for an annular hole cutter which enables a stan-dard size cutter to be easily reduced in diameter to pro-vide a special size cutter.
The preferred form of hole cutter of this inven-tion has an annular side wall formed with a plurality of circumferentially spaced teeth around its lower end and a corresponding number of helical flutes around its outer perip~ry. Eaah too~h i8 formed with a plurality of cir-cumferentially, and preferably vertically staggered, cutting edges, at least two of the cutting edges being formed on that portion of the tooth which corresponds to the thickness of the web between successive teeth and the remaining cutting edges being formed on that portion of the tooth which corresponds to the radial depth of the flute~ The combined width of the two radially inner ~ cutting edges is preferably greater than the combined width of the remaining cutting edges, in which case the thickness of the web is greater than the depth of the flute. In addition, the depth of the flute is preferably at least as great as the width of the widest of the two inner cutting edges. The wall thickness of the cutter is designed to produce a relatively narrow cutting path so as to maintain the power required to feed the cutter through a workpiece at a reasonably low value.
Other objects, features and advantages of the present invention will become apparent from the follow-ing description and accompanying drawings, in which:
FIGURE 1 is a perspective view of one form of cutter according to the present invention;
FIGURE 2 is an enlarged fragmentary view of a portion of the cutt~r shown in FIG. 1 which is designated by the circle 2;
FIr~U~E 3 is a fragmentary sectional view of the cutter along the line 3-3 in FIG. l;
FIGURE 4 is a fragmentary, slightly perspective, sectional view of one tooth of the cutter;
FIGURE 5 is a perspective view of another form of cutter according to the present invention;
FIG~RE 6 is an ~nlarged fragmentary view of a portion of the cutter shown in FIG.-5 which is designated by the circle 6; ~- -FIGURE 7 is a slightly perspective, sectional view of one tooth of the cutter shown in FIG. 5;
FIGURE 8 is a fragmentary bottom view on an enlarged scale showing the cutter in relation to the workpiece through which it is being fed; and FIGURE 9 is a fragmentary perspective view of a further cutter which is slightly modified with respec*
to the cutter shown in FIGS. 5 through 8.
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Referring to the drawings, the annular hole cutter of this invention is generally designated 10 and includes a cutter body 12 and a shank 14. Cutker body 10 is of inverted cup shape having a side wall 16 and a top wall 180 The lower end of side wall 16 is formed wi~h a plurality o cutting teeth 20 which are preferably xegularly spaced.~ A s~ir~l flute 22 extends upwardly around the outer periphery of the cutter adjacent each tooth 20. The successive flutes 22 are separated by a land 24 at the outer periphery of the cutter. In the cutter illustrated the flutes and lands extend the full length of the cutter side wall. For some applications the cutter pe~forms even ~ors sffectively when the flutes and lands are substantially shorter than tXe side wall.
The portions of the annular side wall of the cutter be- ~ ~
tween the successive teeth 20 comprise webs 26. The radially outer face 28 of each web 26 defines the radially inner wall of each flute 22. Each flute 22 includes a leading side wall 30 and a trailing side wall 32.
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In the form of cutter illustrated in FIGS. 1 through 4 each tooth 20 is formed with three cutting edges 34,36,38. The cutting edge 34 is spaced forwardly in the direction of rotation from the cutting edge 36 and the cutting edge 36 is spaced forwardly in the di-rection of rotation from cutting edge 38. Cutting edge 34 is located at the lower end of the trailing face 40 of an inner gullet 420 The upper end of gullet 42 in~
- cl~nes radially outwardl~ in an upward direction as at 44. Cutting edge 36 is located at the lower end of the trailing face 46 of a secondary gullet 48 which is formed in web 26 directly adjacent the inner gullet 44~ The upper end of secondary gullet 48 is curved upwardly in a radially outward direction as at 50. Cutting edges 34, 36 are separated by a circumferentially extending shoulder 51 at the lower end of the radially inner face 52 of gullet 48. Cutting edge 38 is located at the lower end of the trailing face 32 of flute 22 and is spaced rear-wardly from cutting edge 36 by a shoulder 54 at the lower end of flute 22.
The bottom face of each tooth is ormed with two back-off or clearance faces 56,58~ In the operative condition of the cutter back-of face 56 inclines axially upward and radially inwardly while back-off face 58 i~-clines axially upwardly and radially outwardlyr In addition, each of these back-off faces inclines upwardly from the respective cutting edges in a circumferential direction to a slight extent, say 5 to 20O, t~ provide the necessary clearance for the cutting edges. The two back-off faces 56,58 intersect in a crest 60 which inter-sects the radially outermost cutting edge 38. While the back-off faces 56,58 can be ground so that the crest 60 intersects any one of the cutting edges, it is preferred in most instances to have this crest intersec~ the outer-most cutting edge. As a result of the inclinations of back-off faces 56,58, cutting edges 34,36,38 are inclined axially and are staggered vertically as well as circum-ferentially.
One of the important features of the cutter of this invention resides in the fact that at the lower end of each tooth web 26 has a radial dimension which is pre-ferably greater than the radial depth of the adjacent flute Z2. Since the cutting edges 34,36,38 are circum-ferentially staggered as shown, as the cutter is rotated and fed into a workpiece a separate chip will be cut by each of the cutting edges. The relative dimensions of the cutter are such that the radial depth of flute 22 is not substantially less than and preferably greater than the wider of the two cutting edges 34,36. Thus, immed-iately after being cut the chip cut by the cutting edge 10 .
34 is directed into flute 22 by the radial inclinationof this cutting edge and the upper end portiGn 44 of gullet 42. Likewise, immediately after being cut the chip cut by cutting edge 36 is directed by radial in-5 clination of this cutting edge and the curved wall 50of gullet 48 into flute 22. The axial dimension of secondary gullet 48 is preferably not substantially greater than the axial dimension of gullet 42 so as to promote immediate discharge of ~he chip into flute 22 and 10 thus avoid the tendency for the accumulation and packing of chips in gullet 48. While the inclination of cutting edge 34 has a tendency to direct the chip cut thereby up-wardly and outwardly, the circumferential extent of the gullet 42 should be sufficiently small to prevent the chip 15 cut by edge 34 from curling to any great extent directly in gullet 42. If gullet 42 is sufficiently small in a circumferential direction, the chip cut by edge 34 tends to remain relatively straight and is directed more reaa-ily upwardly and outwardly of the gullet. The circumfer-20 ential width of inner gullet 42 should preferably benot greater than about one-half the thickness of web 26 and on the order of about one-third the thickness o:E
web 26. The circumferential dimension of gullet 42 should vary inversely with the thickness of web 26. Thus, 25 immediately after being cut, the chips formed by cutti~
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edges 34,36 are directed radially outwardly an~ axially upwardly into flute 22. The chip cut by cutting edge 38 is likewise directed upwardly in flute 22.
Since each of these chips is relatively narrow and tend to form axial, rather than radial, spirals, they are effectively directed in a radially outward direc~ion by the gullets. As the spiral chips from each of the cutting edges move in an axially upwardly and radially outward direction into flute 22, they tend to becorae intertwined with one another. As soon as the intertwined spiral chips contact the wall of the hole being formed, the friction created thereby tends to arrest rotation of the chips with the cutter. As this occurs, the trailing face 32 of the flute in which they are located engages the spiral chips and cams them upwardly out of the flute.
Since the spiral chips are narrow they can easily become compressed between the inner face 28 of the flute and the wall of the hole being ~ormed in the workpiece. Sin~e the trailing face 32 of each flute 22 is formed as a con-tinuous spiral, the flow of chips upwardly in the flutesis continuous, smooth and unimpeded. Thus, if the gullets 42,48 are shaped and dimensioned so as to direct the chips cut by the cutting edges 34,36 substantially immediately into the flute 22 and since the flow of chips in an upwardly direction through the flute is unimpeded 12.
or unobstructed, a free flow of chips upwardly out o the flute i5 assured. The free flow of small chips up the flute is more readily effected when the cutter is supplied internally with coolant under pressure. In addition, since the chips are narrow and inherently weak, they tend to break readily on exodus from the hole and, thus, do not tend to wrap around the cutter and/or arbor as they exit from the hole being cut and, thus, block or impede the further exodus of chips subsequently cut. Further-more, as mentioned previously, if gullet 42 is narrow ina circumferential direction, the tendency for the chip cut by edge 34 to curl is impeded so that it is directed into flute 22 in a more straightened condition. This reduces the likelihood ~f t-he chip becoming wedged in and clog-ging the gullet and fl~te I~ it is desired to provide a slight clearancebetween the inner periphery of wall 16 and the cylindri-cal slug being cut, the inner periphery of wall 16 may be tapered outwardly at an angle of about 1 from the lower end thereof for a short distance, ~or example, 1/2 inch, as is indicated at 62 in FIG. 3. The portion of the inner periphery of the cutter side wall rnay be made cylindrical above the tapered portion as indicated at 64. Thus, at a short distance above the cutting edges the inner periphery of the cutter will have a clearance of about .008 inches ~.~53i with the outer cylindrical surface of the slug being cut from the workpiece. Also as shown in FIG. 3, if desired, the depth of flute 22 can be made progressively greater in an upward direction by grinding the inner face 28 of the flute so that it tapers radially inwardly up to the section 62 at a slightly greater rate in an upward direc-tion than above this section. This provides radial clear-ance for the chip cut by edge 38 immediately after being cut. Thus, the flute as a whole may be provided with a cross section of increasing area in an upward direction to more readily facilitate the ejection of chips there-from. Each flute may also be tapered so that it is cir-cumferentially wider at its upper end than at its lower end.
The provision of a heavy web section while still-maintaining the width of all chips very narrow also has the advantage of permitting an axially deeper inner gulletO
An axially deeper gullet not only promotes a greater fl~w of coolant across the cutter teeth, but also permits the teeth to be sharpened for a longer period of time before regrinding the gullets becomes necessary.
It will be appreciated that in order to reduce the power requirements for feeding an annular cutter int~
a workpiece such as steel, it is necessary that the cutting path or groove formed by the cutter be relativel~
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narrow. For a cutter designed to cut a hole in steel, a practical dimension for the wall thickness of the annular cutter is about .160 to o180 inches. When each tooth is formed with three cutting edges such as shown in FIGS. 1 through 4 and the side wall of the cutter is approximately .160 inches thick, the radial depth of flute 22 can be on the order of ~070 inches and, thus, the thickness of web 26 can be approximately .090 inches. The two inner cutting e~ges 34,36-can ha~e a width of approximately .045 inches or, if desired, the innermost cutting edge 34 can have a width of about .040 inches and the intermediate cutting edge 36 can have a width of about .050 inches.
Thus, with a relatively heavy web and a relatively thin annular wall each of the chips ~ut by the three cuttiny edges can be readily accon~odated in the flute 22. The circumferential dimension of each flute is preferably several times greater than the radial depth of each flute.
The cutter shown in FIGS. 5 through 8 differs in design from that shown in FIGS. 1 through 4 essential-ly in only one feature. In the cutter shown in FIGS~ 5through 8 the portion of each tooth which corresponds to the depth of the flute 22 is formed with two cutting edges 70,72 rather than with a single cutting edge as shown at 38 in FIGS. 1 through 4. If the side wall 16 of the cutter has a thickness of approximately .160 15.
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inches, then the cutter can be desiyned so that flute 22 has a depth of about .064 inches and web 26 has a thick-ness of about .096 inches. In this case each of the cutting edges 34,36 can be about 0.48 inches wide and each of the cutting edges 70,72 can be about .032 inches wide. The back-off faces 56,58 on each tooth are inclin-ed in a manner as previously described with reference to FIGS. 1 through 4 and preferably intersect at a crest 74 which, in turn, intersects the outermost cutting edge 72 at approximately the center thereof.
In the cutter illustrated in FIGS. 5 through 8 cutting edge 72 is staggered circumferentially from cutting edge 70 a very slight amount such that these cutting edges produce a single chip having a central line of weakness. ~s a practical matter, in a cutter de-signed for cutting holes in steel, edge 72 should be staggered only about one-quarter of the extent of the stagger of the other teeth, preferably not more than about .015 inches. The deformed single chip thus cut by edges 70,72 is very susceptible to fracture as soon as it encounters an obstruction. However, this single weak chip is directed immediately into the large flute 22 which eliminates the tendency for narrow chips to become packed in the portion of the flute between shoulder 82 (FIG. 8) and the side wall 76 of the hole being formed.
16.
~h.~ 36 If edge 72 i5 staggered rearwardly from edge 70 such that each of these edges cut individual chips, then it is preferred that the portion of flute 22 associated with edge 72 be formed as a gullet 84 (FIG. 9) having a vertical extent substantially equal to the vertical ex-tent of gullets 44,50. Thus, when edge 72 is staggered sufficiently to cut a separate chip, the chip so cut is directed by gullet ~4 immediately into the large flute 22 and does not tend to cl~g gullet 84.
When the cutter shown in FIG. 9 is rotated and fed into a workpiece, four separate chips will be cut by the cutting edges 34,36 and 70,72. With the cutter shown in FIGS. 5 through 8 edges 34,36 will each cut separate chips and, as explained previously, edges 70,72 will cut a.single readily b.reakable chip. In either case, the chip cut by cutting edge 34 will be substantially immedi-ately directed outwardly into flute 22 and the chip cut by cutting edge 36 will also be substantially immediately directed upwardly and outwardly into flute 22. Likewise, the single or separate chips cut by cutting edges 70,72 will be directed upwardly in flute 22.
However, substantially immediately after the chips are cut by cutting edges 34,46,70 and directed into flute 22 they will come into frictional contact with the side wall 76 of the hole being formed in the workpiece.
~5~3536 Since the chips which have not fractured will normally have a somewhat spiral configuration, as they engage the side wall the frictional resistance created thereby will have a tendency to arrest rotation of the spiral chips with the cutter. ~s a result, the chips will be sub-stantially immediately engaged by the trailing side wall portion 78 of flute 22 (FIG. 6) and, in the manner pre-viously described, they will be cammed upwardly out of the flute without obstruction. Thus, because of the small circumferential extent of shoulder 82, with the cutter shown in FIGS. 5 through 8 the chips will not be engaged by and thus trapped by the trailing side wall portion 80 of flute 22. This is desirable since the tendency for any chips to become wedged between the outer periphery of the cutter and the side wall 76 of the hole being formed is substantially reducedO In addition, since the chips are narrow they are less likely to score the wall of the hole being formed as they flow upwardly through the flutes. Furthermore, the narrow chips are readily fractured upon exodus from the hole being formed and, thus, do not tend to wrap around the cutter and/or arbor and, thus, impede the free flow of the chips sub-sequently formed.
18.
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The provision of four circumferentially and vertically staggered cutting edges such as shown in FIGS. 5 through 8 and FIG. 9 has several other desirable advantages over the cutter shown in FIGS. 1 through 4.
In the first place, all of the cutting edges in these cutters can be narrower than the three cutting edges shown in the cutter shown in FIGS. 1 through 4 even though both cutters have the same web thickness and the same flute depth. Thus, the chips formed by these cutting edges can be even more readily disch~rged and ejected upwardly through the flutes 22. Another ad-vantage of the configurations shown in FIGS . 5 through 8 and FIG. 9 wherein the portion of the tooth corre-sponding to the depth of the flute is provided with two, rather than one, cutting edges resides in the fact that~
if it is desired to provide a cutter having an outer diameter of say .020 inches smaller than a standard size cutter, it is only necessary to take a finished standard size cutter and grind .010 inchres off the outer periphery thereof. Thus, the depth of flute 22 19.
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will be reduced by only .010 inches and will still be sufficiently great to accommodate the width of the chips cut by the other three cutting edges. It will be appre-ciated that, even with the cutter shown in FIGS. 1 through 4, the outer diameter of the cutter can be ground down to produce a special size cutter, provided that the radial depth of the resulting flute is still substantially as large as the width of the widest chip cut.
A Eu~her advantage of the cutter having at least two cutting edges in both the web section and in the portion of the tooth corresponding to the flute depth resides in the fact that when a metal chip is cut it tends to expand as much as 10%. With cutters as shown in FIGS. 5 through 8 and FIG. 9 the depth of flute 22 is more than 10% greater than the width of the largest cutting edge. Thus, the tendency for any of the expand-ing chips to bind or clog in flute 22 is even further reduced. Even ~hough the edges 70,72 of the cutter shown in FIGS. 5 through 8 cut a single chip, the chip has a central line of weakness and thus readily breaks into small narrow chips.
20.
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With a cutter of the present invention the ease of chip ejection and other advantages are obtained with-out sacrificing any strength in the cutter. This is true because at least three, and preferably four or more, cutting edges are provided on each tooth and the depth of the flute can be substantially less than the width or thickness of the web portion between successive teeth.
The strength of an annular cutter having a fluted side wall is determined primarily by the thicknes~ of the web.
Thus, if it is determined on a particular cutter that the web must have a predetermined minimum thickness, then the total wall thickness of a cutter of the present invention can be less than on a prior art cutter since with the present invention the depth of the flute can be less than the thickness of the web and still sufficient to accommo-date the widest chip cut by any of the cutting edges. A
thinner side wall is desirable from the standpoint of cost as well as a narrow cutting path.
Another advantage of a cutter constructed in accordance with this invention is apparent from the show-ing in FIG. 3. As pointed out above, adjacent each tDoth the thickness of th~ web 26 can be substantially greater than the depth of flute 22. This results from the fact that the portion of the tooth corresponding to the web thickness is formed with at least two cutting edges, each ~ J~3~
of which has a width which is preferably substantially less than the depth of the flute~ Thus, if the inner wall 28 of the flute is tapered radially inwardly in an upward direction immediately adjacent its lower end and relatively sharply up to about the section designated 62 in FIG. 3, the chip cut by edge 38 has immediate clear-ance with the flute. ~ikewise, when the inner periphery of the cutter adjacent its lower end is tapered radially out~rdly in an upward direction, tha web 2~ has its mini-mum thickness adjacent the upper end of the cutter sidewall at the region designated 86 in FIG. 3. This section 86 then becomes the critical section of the cutter insofar as its strength is concerned. It therefore follows that with a conventional prior art cutter where the depth of a flute adjacent the tooth of the cutter--is as great as the thickness of the web, then the total wall thickness of the cutter would have to be substantially greater if the cutter were formed with a flute of increasing depth in an upward direction and with clearance around the inner periphery thereofO It also follows that with a cutter of this invention a substantially greater clearance around the inner periphery of the cutter can be obtained ~ithout the need for substantially increasing the wall thic~ness of the cutter~ Greater clearance is also desirable with respect to the ability to increase the flow of cool3nt to the cutter teeth.
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Y~ 5~Çi ~ he provision of a relatively thick web and a relatively shallow flute in an annular cutter is also very important rom the standpoint of manufacturing. With a given wall thickness, when it is attempted to grind a relatively deep flute in the side wall, there is a very strong tendency to develop small hairline cracks in the web which can result in relatively short tool life. Re-latively deep flutes also increase the tendency for hair-line cracks to develop during heat treatment. How2ver, if the flute is relatively shallow and the web is rela-tively thick, the web portion can absorb substantially more heat and, thus, substantially reduce the tendency for such cracks to develop during heat treatment and grinding of the flutes. A shallow flute is also desir-able from the standpoint of the cost of manufacture.It can be machined or ground in less time and results in proportionally greater -tool lifeO
Although not shown in the drawings, a majority of annular cutters require a center pilot pin or a center pilot drillO As a practical matter, the bore 88 in shank 14 for retaining the pilot pin or pilot drill has to be at least of a predetermined sizeO Thus, the inner diam-eter of the cutter has to be at least equal to the diameter of the pilot pin or pilot drill. Since the cutter of this invention has a web which can be thicker than the depth of ' 23.
the flute, it follows that with a pilot hole of predeter-mined size the outer diameter of a cutter according to the present invention can be less than the minimum prac~
tical outer diameter of a cutter constructed in accordance with the prior art.
Another advantage which flows from the fact that the present cutter has a thicker web section as com-pared with prior art cutters is that it can be made in two pieces, a tooth section and a body section, axially telescoped together in the web section and secured to one another by threads, welding, etc. The thicker web allows such telescopic connection without substantially affecting the strength of the cutter. A cutter of such two-piece construction has the obvious advantage of cost.
lS Onl~ the tooth section need be of expensive steelO
Furthermore, when the teeth become worn, only the tooth section need be replaced rather than the entire cutterO
A thicker web section also permits the forming of more teeth around the periphery of the cutter since it can withstand more torque and thrust. A greater number of teeth results in more cutting edges and faster cutting action.
24.
I have determined that from the standpoi.nt of maximum strength of the cutter in relation to the ease of ejection of the chips the thicXness of the web between successive teeth should be at least 55 to 60% o the thick-ness of the annular wall of the cutter. In the case ofcutters of the type illustrated in FIGS. 5 through 8 and FIG. 9 where each tooth is formed with four cutting edges, in the absence of special considerations, it is preferred to form the two inner cutting edges to about the same width and the two outer cutting edges to about the same width.
However, special consideration may dictate otherwise; or example, if it is desired to cut a very smooth surface on the central cylindrical slug, then the innermost cutting edge 34 should be substantially narrower than the next radially successive cutting edge 36. In any event, the wider of these two edges should not be wider than the depth of flute 22. on the other hand, i-f it is desired to cut an extremely smooth hole in a workpiece, then the outermost cutting edge 72 should be considerably narrower than the next radially successive cutting edge 70. If it is desired to cut both a smooth wall hole and a central - slug having a smooth side wall, then the innermost and outermost cutting edges should be narrower than the inter-mediate cutting edges. In any event, where the cutter is designed for cutting holes in steel and has at least four 3~
cutting edges, best results are normally obtained where the widest cutting edge has a width of not more than about .0625 inches. However, if increased rigidity is desired, this cutting edge width can be increased consid-erably by as much as two or three times.
Likewise, although it is preferred to form the crest between back-off faces 56,58 so that it intersects the outermost cutting edge, for certain applications the back-off faces may be ground so that the crest intersects one of the other cutting edges~ For example, if the cutter is being used to form a hole in two or more work-pieces which are stacked on one another, then the crest between the two back-off faces should lie very close to the inner periphery of the side wall of the cutter~ If the crest or the high point of the cutter is located closely adjacent the inner periphery of the cutter side wall, little difficulty is encountered in feeding the~
cutter through both of the overlying workpieces.
The high point of the cutter can be shifted to the inner cutting edge 34 without changing the location of crest 74. Since the back-off face 56 inclines upward-ly in a circumferential direction, it follows that if the shoulders 51,5~ are increased in length sufficiently, crest 74 will be spaced above, rather than below, edge 34.
In this case edge 34 will initiate the cutting action and 26.
3~
will penetrate through the uppermost workpiece before crest 74. Thus, if edge 34 is maintained at a very small width, the small lip remaining on the cut slug will not prevent it from moving up into the bore of the cutter so that the cutter can freely penetrate through the under-lying workpiece.
Since a chip tends to expand slightly immediate-ly after being cut, it is desirable to grind surface 28 of flute 22 so that the flute has its maximum radial depth at the junction of surfaces 28,32. This reduces to a minimum the frictional resistance of the chip cut by edge 38 against inner wall of the flute.
.
This invention relates to an annular hole cutter.
In my prior U.S. Reissue Patent No. 28,416 there is disclosed an annular cutter having a plurality of teeth spaced around the leading (lower) end of the cutter. Each tooth is provided with a plurality of circumferentially staggered cutting edges. The cutting edges are designed so that each will cut its own chip.
- The ~adially inr3ermost cutting edge exte~ds radially across a shallow gullet formed in the web between suc-cessive teeth and the outermost cutting edge extends radially across an outer flute which extends spirally upwardly of the cutter between successive teeth. In accordance with the teaching of my prior patent, the flute has a radial depth equal to about one-half the thickness of the annular wall of the cutter and the web has a thickness equal to about one-half the thick-ness of the annular wall. Consequently, the radially inner cutting edge of each tooth has a radial extent also equal to about one~half the wall thickness of the cutter. Thus, the flute has a radial depth which is sufficient to accommo~ate the discharge of chips cut by both cutting edges.
The prior patent referred ko also suggests that, if it is desired to provide three circumferen-tially staggered cutting edges on each tooth so that each tooth cuts three chips instead of two, the radial depth of the flute and the thickness of the web are maintained the same as for the two step tooth cutter and the portion of the cutter wall which corresponds to the depth of the flute is formed into two circumferen-tially staggered cutting edges Pather than a single cutting edge. The radially outermost cutting edge is defined by an outer gullet which has a relatively short axial dimension and opens into the ~lute. ~owever, the flute still has a radial dimension equal approximately to one-half the wall thickness of the cutter so that it can readily accommodate the chip cut by the radially innermost cutting edge.
While the cutter disclosed in my prior patent produces cutting action which is far superior to annular cutters previously used, under some conditions of feeds and speeds there is a tendency for the chips to become packed in the inner gullet and the flute. When this occurs the cutting action is much slower and a tapered - . oversized hole with a coarser finish is produced. In addition, the life of the cutting edge is substantially sho~tened. I have determined that the most practical $~6 way of overcoming this problem of chip packing in the flute of an annular cutter is to provide a cutter design which will produce thin, narrow chips.
Normally as soon as a chip is cut it begins to curl into a spiral. The volume and stiffness of a spiral chip is determined by its width and thickness. If a chip is wide it does not bend readily and occupies a relative-ly large volume. The net result of a large volume spiral chip is that less chip ma~erial can flow upwardly through the passageway defined by a flute in a given amount of time. However, if a chip is narrow it bends easily when it encounters an obstruction, such as the wall of a flute or hole, and requires far less flute depth as it moves upwardly through a flute-. A narrow chip can also be easily distorted beyond its elastic limit and thus frac-tures easily into smaller fragments. In addition, a narrow chip forms a radially compressible, spring-like spiral helix which is adapted to intertwine with other~
as it moves up a spiral flute. When such intertwined spiral chips engage the wall of the hole being formed by the cutter, the resultiny friction tends to resist their further rotation with the cutter which causes them to be forcibly cammed upwardly by the trailing side wall of the helical flute without clogying the flute. Thus it follows that a flute can be reduced in cross sectio~al L. ~
area as the width of the chip is reduced. ~t also follows that with a cutter side wall of a given thickness, as the size of the flute is reduced, the strength of the cutter is increased since the web between successive teeth will be thickerO A thicker web provides greater rigidity, thus producing a more accurate hole with a better finish. With increased cutter strength a thicker chip may be cut and/or a greater number of teeth may be used; thus a faster cutting action is also obtained.
The primary object of this invention is to pro-vide an annular cutter which cuts more efficiently, more rapidly, and more accurately; produces a better finish;
has a longer life and which, at the same time, has a greater resistance to breakage than an equivalent size cutter of the prior art.
A more specific object of this invention is to provide a fluted annular cutter wherein each tooth has a plurality of at least three cutting edges thereon, each of which preferably has a radial dimension substantially less than one-half the wall thickness of the cutter so that the radial dimension of the flute can be as small as about one-third the wall thickness of the cutter and still sufficiently deep to freely accommodate the chip cut by the widest cutting edge~
;i3~
Another object of this invention is to provide an annular hole cutter which is more efficient and has a higher strength than prior art cutters of the same size.
This is obtained by forming each tooth of the cutter with at least three cutting edges, each of which is adapted to cut a separate chip and two of which are formed on that portion of the cutter side wall located radially inwardly of the flute, that is, in the web section between suc-cessive teeth.
Another object of the invention is to provide an annular cutter which is admirably adapted to be form-ed as two axially adjacent sections telescopically join-ed together so that ~he leading end portion of the cutter on which the teeth are formed can be made of a relatively expensive cutting tool ~laterial, such as high speed steel, and the body portion of the cutter made of a less expensive material, such as a heat-treated, relatively low alloy steel.
Another object of the invention is to provide a design for an annular hole cutter thak enables the manufacture of cutters of small diameter and with sub-stantially less tendency to develop hairline cracks when the flutes are ground or heat treated.
5.
~ ~J/~ ~3 ~
A further object of the invention is to provide a design for an annular hole cutter which enables a stan-dard size cutter to be easily reduced in diameter to pro-vide a special size cutter.
The preferred form of hole cutter of this inven-tion has an annular side wall formed with a plurality of circumferentially spaced teeth around its lower end and a corresponding number of helical flutes around its outer perip~ry. Eaah too~h i8 formed with a plurality of cir-cumferentially, and preferably vertically staggered, cutting edges, at least two of the cutting edges being formed on that portion of the tooth which corresponds to the thickness of the web between successive teeth and the remaining cutting edges being formed on that portion of the tooth which corresponds to the radial depth of the flute~ The combined width of the two radially inner ~ cutting edges is preferably greater than the combined width of the remaining cutting edges, in which case the thickness of the web is greater than the depth of the flute. In addition, the depth of the flute is preferably at least as great as the width of the widest of the two inner cutting edges. The wall thickness of the cutter is designed to produce a relatively narrow cutting path so as to maintain the power required to feed the cutter through a workpiece at a reasonably low value.
Other objects, features and advantages of the present invention will become apparent from the follow-ing description and accompanying drawings, in which:
FIGURE 1 is a perspective view of one form of cutter according to the present invention;
FIGURE 2 is an enlarged fragmentary view of a portion of the cutt~r shown in FIG. 1 which is designated by the circle 2;
FIr~U~E 3 is a fragmentary sectional view of the cutter along the line 3-3 in FIG. l;
FIGURE 4 is a fragmentary, slightly perspective, sectional view of one tooth of the cutter;
FIGURE 5 is a perspective view of another form of cutter according to the present invention;
FIG~RE 6 is an ~nlarged fragmentary view of a portion of the cutter shown in FIG.-5 which is designated by the circle 6; ~- -FIGURE 7 is a slightly perspective, sectional view of one tooth of the cutter shown in FIG. 5;
FIGURE 8 is a fragmentary bottom view on an enlarged scale showing the cutter in relation to the workpiece through which it is being fed; and FIGURE 9 is a fragmentary perspective view of a further cutter which is slightly modified with respec*
to the cutter shown in FIGS. 5 through 8.
.~.Yi..~ 3~;
Referring to the drawings, the annular hole cutter of this invention is generally designated 10 and includes a cutter body 12 and a shank 14. Cutker body 10 is of inverted cup shape having a side wall 16 and a top wall 180 The lower end of side wall 16 is formed wi~h a plurality o cutting teeth 20 which are preferably xegularly spaced.~ A s~ir~l flute 22 extends upwardly around the outer periphery of the cutter adjacent each tooth 20. The successive flutes 22 are separated by a land 24 at the outer periphery of the cutter. In the cutter illustrated the flutes and lands extend the full length of the cutter side wall. For some applications the cutter pe~forms even ~ors sffectively when the flutes and lands are substantially shorter than tXe side wall.
The portions of the annular side wall of the cutter be- ~ ~
tween the successive teeth 20 comprise webs 26. The radially outer face 28 of each web 26 defines the radially inner wall of each flute 22. Each flute 22 includes a leading side wall 30 and a trailing side wall 32.
8.
3~
In the form of cutter illustrated in FIGS. 1 through 4 each tooth 20 is formed with three cutting edges 34,36,38. The cutting edge 34 is spaced forwardly in the direction of rotation from the cutting edge 36 and the cutting edge 36 is spaced forwardly in the di-rection of rotation from cutting edge 38. Cutting edge 34 is located at the lower end of the trailing face 40 of an inner gullet 420 The upper end of gullet 42 in~
- cl~nes radially outwardl~ in an upward direction as at 44. Cutting edge 36 is located at the lower end of the trailing face 46 of a secondary gullet 48 which is formed in web 26 directly adjacent the inner gullet 44~ The upper end of secondary gullet 48 is curved upwardly in a radially outward direction as at 50. Cutting edges 34, 36 are separated by a circumferentially extending shoulder 51 at the lower end of the radially inner face 52 of gullet 48. Cutting edge 38 is located at the lower end of the trailing face 32 of flute 22 and is spaced rear-wardly from cutting edge 36 by a shoulder 54 at the lower end of flute 22.
The bottom face of each tooth is ormed with two back-off or clearance faces 56,58~ In the operative condition of the cutter back-of face 56 inclines axially upward and radially inwardly while back-off face 58 i~-clines axially upwardly and radially outwardlyr In addition, each of these back-off faces inclines upwardly from the respective cutting edges in a circumferential direction to a slight extent, say 5 to 20O, t~ provide the necessary clearance for the cutting edges. The two back-off faces 56,58 intersect in a crest 60 which inter-sects the radially outermost cutting edge 38. While the back-off faces 56,58 can be ground so that the crest 60 intersects any one of the cutting edges, it is preferred in most instances to have this crest intersec~ the outer-most cutting edge. As a result of the inclinations of back-off faces 56,58, cutting edges 34,36,38 are inclined axially and are staggered vertically as well as circum-ferentially.
One of the important features of the cutter of this invention resides in the fact that at the lower end of each tooth web 26 has a radial dimension which is pre-ferably greater than the radial depth of the adjacent flute Z2. Since the cutting edges 34,36,38 are circum-ferentially staggered as shown, as the cutter is rotated and fed into a workpiece a separate chip will be cut by each of the cutting edges. The relative dimensions of the cutter are such that the radial depth of flute 22 is not substantially less than and preferably greater than the wider of the two cutting edges 34,36. Thus, immed-iately after being cut the chip cut by the cutting edge 10 .
34 is directed into flute 22 by the radial inclinationof this cutting edge and the upper end portiGn 44 of gullet 42. Likewise, immediately after being cut the chip cut by cutting edge 36 is directed by radial in-5 clination of this cutting edge and the curved wall 50of gullet 48 into flute 22. The axial dimension of secondary gullet 48 is preferably not substantially greater than the axial dimension of gullet 42 so as to promote immediate discharge of ~he chip into flute 22 and 10 thus avoid the tendency for the accumulation and packing of chips in gullet 48. While the inclination of cutting edge 34 has a tendency to direct the chip cut thereby up-wardly and outwardly, the circumferential extent of the gullet 42 should be sufficiently small to prevent the chip 15 cut by edge 34 from curling to any great extent directly in gullet 42. If gullet 42 is sufficiently small in a circumferential direction, the chip cut by edge 34 tends to remain relatively straight and is directed more reaa-ily upwardly and outwardly of the gullet. The circumfer-20 ential width of inner gullet 42 should preferably benot greater than about one-half the thickness of web 26 and on the order of about one-third the thickness o:E
web 26. The circumferential dimension of gullet 42 should vary inversely with the thickness of web 26. Thus, 25 immediately after being cut, the chips formed by cutti~
11 .
53~
edges 34,36 are directed radially outwardly an~ axially upwardly into flute 22. The chip cut by cutting edge 38 is likewise directed upwardly in flute 22.
Since each of these chips is relatively narrow and tend to form axial, rather than radial, spirals, they are effectively directed in a radially outward direc~ion by the gullets. As the spiral chips from each of the cutting edges move in an axially upwardly and radially outward direction into flute 22, they tend to becorae intertwined with one another. As soon as the intertwined spiral chips contact the wall of the hole being formed, the friction created thereby tends to arrest rotation of the chips with the cutter. As this occurs, the trailing face 32 of the flute in which they are located engages the spiral chips and cams them upwardly out of the flute.
Since the spiral chips are narrow they can easily become compressed between the inner face 28 of the flute and the wall of the hole being ~ormed in the workpiece. Sin~e the trailing face 32 of each flute 22 is formed as a con-tinuous spiral, the flow of chips upwardly in the flutesis continuous, smooth and unimpeded. Thus, if the gullets 42,48 are shaped and dimensioned so as to direct the chips cut by the cutting edges 34,36 substantially immediately into the flute 22 and since the flow of chips in an upwardly direction through the flute is unimpeded 12.
or unobstructed, a free flow of chips upwardly out o the flute i5 assured. The free flow of small chips up the flute is more readily effected when the cutter is supplied internally with coolant under pressure. In addition, since the chips are narrow and inherently weak, they tend to break readily on exodus from the hole and, thus, do not tend to wrap around the cutter and/or arbor as they exit from the hole being cut and, thus, block or impede the further exodus of chips subsequently cut. Further-more, as mentioned previously, if gullet 42 is narrow ina circumferential direction, the tendency for the chip cut by edge 34 to curl is impeded so that it is directed into flute 22 in a more straightened condition. This reduces the likelihood ~f t-he chip becoming wedged in and clog-ging the gullet and fl~te I~ it is desired to provide a slight clearancebetween the inner periphery of wall 16 and the cylindri-cal slug being cut, the inner periphery of wall 16 may be tapered outwardly at an angle of about 1 from the lower end thereof for a short distance, ~or example, 1/2 inch, as is indicated at 62 in FIG. 3. The portion of the inner periphery of the cutter side wall rnay be made cylindrical above the tapered portion as indicated at 64. Thus, at a short distance above the cutting edges the inner periphery of the cutter will have a clearance of about .008 inches ~.~53i with the outer cylindrical surface of the slug being cut from the workpiece. Also as shown in FIG. 3, if desired, the depth of flute 22 can be made progressively greater in an upward direction by grinding the inner face 28 of the flute so that it tapers radially inwardly up to the section 62 at a slightly greater rate in an upward direc-tion than above this section. This provides radial clear-ance for the chip cut by edge 38 immediately after being cut. Thus, the flute as a whole may be provided with a cross section of increasing area in an upward direction to more readily facilitate the ejection of chips there-from. Each flute may also be tapered so that it is cir-cumferentially wider at its upper end than at its lower end.
The provision of a heavy web section while still-maintaining the width of all chips very narrow also has the advantage of permitting an axially deeper inner gulletO
An axially deeper gullet not only promotes a greater fl~w of coolant across the cutter teeth, but also permits the teeth to be sharpened for a longer period of time before regrinding the gullets becomes necessary.
It will be appreciated that in order to reduce the power requirements for feeding an annular cutter int~
a workpiece such as steel, it is necessary that the cutting path or groove formed by the cutter be relativel~
1~ .
ii3~
narrow. For a cutter designed to cut a hole in steel, a practical dimension for the wall thickness of the annular cutter is about .160 to o180 inches. When each tooth is formed with three cutting edges such as shown in FIGS. 1 through 4 and the side wall of the cutter is approximately .160 inches thick, the radial depth of flute 22 can be on the order of ~070 inches and, thus, the thickness of web 26 can be approximately .090 inches. The two inner cutting e~ges 34,36-can ha~e a width of approximately .045 inches or, if desired, the innermost cutting edge 34 can have a width of about .040 inches and the intermediate cutting edge 36 can have a width of about .050 inches.
Thus, with a relatively heavy web and a relatively thin annular wall each of the chips ~ut by the three cuttiny edges can be readily accon~odated in the flute 22. The circumferential dimension of each flute is preferably several times greater than the radial depth of each flute.
The cutter shown in FIGS. 5 through 8 differs in design from that shown in FIGS. 1 through 4 essential-ly in only one feature. In the cutter shown in FIGS~ 5through 8 the portion of each tooth which corresponds to the depth of the flute 22 is formed with two cutting edges 70,72 rather than with a single cutting edge as shown at 38 in FIGS. 1 through 4. If the side wall 16 of the cutter has a thickness of approximately .160 15.
~53~
inches, then the cutter can be desiyned so that flute 22 has a depth of about .064 inches and web 26 has a thick-ness of about .096 inches. In this case each of the cutting edges 34,36 can be about 0.48 inches wide and each of the cutting edges 70,72 can be about .032 inches wide. The back-off faces 56,58 on each tooth are inclin-ed in a manner as previously described with reference to FIGS. 1 through 4 and preferably intersect at a crest 74 which, in turn, intersects the outermost cutting edge 72 at approximately the center thereof.
In the cutter illustrated in FIGS. 5 through 8 cutting edge 72 is staggered circumferentially from cutting edge 70 a very slight amount such that these cutting edges produce a single chip having a central line of weakness. ~s a practical matter, in a cutter de-signed for cutting holes in steel, edge 72 should be staggered only about one-quarter of the extent of the stagger of the other teeth, preferably not more than about .015 inches. The deformed single chip thus cut by edges 70,72 is very susceptible to fracture as soon as it encounters an obstruction. However, this single weak chip is directed immediately into the large flute 22 which eliminates the tendency for narrow chips to become packed in the portion of the flute between shoulder 82 (FIG. 8) and the side wall 76 of the hole being formed.
16.
~h.~ 36 If edge 72 i5 staggered rearwardly from edge 70 such that each of these edges cut individual chips, then it is preferred that the portion of flute 22 associated with edge 72 be formed as a gullet 84 (FIG. 9) having a vertical extent substantially equal to the vertical ex-tent of gullets 44,50. Thus, when edge 72 is staggered sufficiently to cut a separate chip, the chip so cut is directed by gullet ~4 immediately into the large flute 22 and does not tend to cl~g gullet 84.
When the cutter shown in FIG. 9 is rotated and fed into a workpiece, four separate chips will be cut by the cutting edges 34,36 and 70,72. With the cutter shown in FIGS. 5 through 8 edges 34,36 will each cut separate chips and, as explained previously, edges 70,72 will cut a.single readily b.reakable chip. In either case, the chip cut by cutting edge 34 will be substantially immedi-ately directed outwardly into flute 22 and the chip cut by cutting edge 36 will also be substantially immediately directed upwardly and outwardly into flute 22. Likewise, the single or separate chips cut by cutting edges 70,72 will be directed upwardly in flute 22.
However, substantially immediately after the chips are cut by cutting edges 34,46,70 and directed into flute 22 they will come into frictional contact with the side wall 76 of the hole being formed in the workpiece.
~5~3536 Since the chips which have not fractured will normally have a somewhat spiral configuration, as they engage the side wall the frictional resistance created thereby will have a tendency to arrest rotation of the spiral chips with the cutter. ~s a result, the chips will be sub-stantially immediately engaged by the trailing side wall portion 78 of flute 22 (FIG. 6) and, in the manner pre-viously described, they will be cammed upwardly out of the flute without obstruction. Thus, because of the small circumferential extent of shoulder 82, with the cutter shown in FIGS. 5 through 8 the chips will not be engaged by and thus trapped by the trailing side wall portion 80 of flute 22. This is desirable since the tendency for any chips to become wedged between the outer periphery of the cutter and the side wall 76 of the hole being formed is substantially reducedO In addition, since the chips are narrow they are less likely to score the wall of the hole being formed as they flow upwardly through the flutes. Furthermore, the narrow chips are readily fractured upon exodus from the hole being formed and, thus, do not tend to wrap around the cutter and/or arbor and, thus, impede the free flow of the chips sub-sequently formed.
18.
3~
The provision of four circumferentially and vertically staggered cutting edges such as shown in FIGS. 5 through 8 and FIG. 9 has several other desirable advantages over the cutter shown in FIGS. 1 through 4.
In the first place, all of the cutting edges in these cutters can be narrower than the three cutting edges shown in the cutter shown in FIGS. 1 through 4 even though both cutters have the same web thickness and the same flute depth. Thus, the chips formed by these cutting edges can be even more readily disch~rged and ejected upwardly through the flutes 22. Another ad-vantage of the configurations shown in FIGS . 5 through 8 and FIG. 9 wherein the portion of the tooth corre-sponding to the depth of the flute is provided with two, rather than one, cutting edges resides in the fact that~
if it is desired to provide a cutter having an outer diameter of say .020 inches smaller than a standard size cutter, it is only necessary to take a finished standard size cutter and grind .010 inchres off the outer periphery thereof. Thus, the depth of flute 22 19.
~i5~;
will be reduced by only .010 inches and will still be sufficiently great to accommodate the width of the chips cut by the other three cutting edges. It will be appre-ciated that, even with the cutter shown in FIGS. 1 through 4, the outer diameter of the cutter can be ground down to produce a special size cutter, provided that the radial depth of the resulting flute is still substantially as large as the width of the widest chip cut.
A Eu~her advantage of the cutter having at least two cutting edges in both the web section and in the portion of the tooth corresponding to the flute depth resides in the fact that when a metal chip is cut it tends to expand as much as 10%. With cutters as shown in FIGS. 5 through 8 and FIG. 9 the depth of flute 22 is more than 10% greater than the width of the largest cutting edge. Thus, the tendency for any of the expand-ing chips to bind or clog in flute 22 is even further reduced. Even ~hough the edges 70,72 of the cutter shown in FIGS. 5 through 8 cut a single chip, the chip has a central line of weakness and thus readily breaks into small narrow chips.
20.
~ 3~
With a cutter of the present invention the ease of chip ejection and other advantages are obtained with-out sacrificing any strength in the cutter. This is true because at least three, and preferably four or more, cutting edges are provided on each tooth and the depth of the flute can be substantially less than the width or thickness of the web portion between successive teeth.
The strength of an annular cutter having a fluted side wall is determined primarily by the thicknes~ of the web.
Thus, if it is determined on a particular cutter that the web must have a predetermined minimum thickness, then the total wall thickness of a cutter of the present invention can be less than on a prior art cutter since with the present invention the depth of the flute can be less than the thickness of the web and still sufficient to accommo-date the widest chip cut by any of the cutting edges. A
thinner side wall is desirable from the standpoint of cost as well as a narrow cutting path.
Another advantage of a cutter constructed in accordance with this invention is apparent from the show-ing in FIG. 3. As pointed out above, adjacent each tDoth the thickness of th~ web 26 can be substantially greater than the depth of flute 22. This results from the fact that the portion of the tooth corresponding to the web thickness is formed with at least two cutting edges, each ~ J~3~
of which has a width which is preferably substantially less than the depth of the flute~ Thus, if the inner wall 28 of the flute is tapered radially inwardly in an upward direction immediately adjacent its lower end and relatively sharply up to about the section designated 62 in FIG. 3, the chip cut by edge 38 has immediate clear-ance with the flute. ~ikewise, when the inner periphery of the cutter adjacent its lower end is tapered radially out~rdly in an upward direction, tha web 2~ has its mini-mum thickness adjacent the upper end of the cutter sidewall at the region designated 86 in FIG. 3. This section 86 then becomes the critical section of the cutter insofar as its strength is concerned. It therefore follows that with a conventional prior art cutter where the depth of a flute adjacent the tooth of the cutter--is as great as the thickness of the web, then the total wall thickness of the cutter would have to be substantially greater if the cutter were formed with a flute of increasing depth in an upward direction and with clearance around the inner periphery thereofO It also follows that with a cutter of this invention a substantially greater clearance around the inner periphery of the cutter can be obtained ~ithout the need for substantially increasing the wall thic~ness of the cutter~ Greater clearance is also desirable with respect to the ability to increase the flow of cool3nt to the cutter teeth.
.
Y~ 5~Çi ~ he provision of a relatively thick web and a relatively shallow flute in an annular cutter is also very important rom the standpoint of manufacturing. With a given wall thickness, when it is attempted to grind a relatively deep flute in the side wall, there is a very strong tendency to develop small hairline cracks in the web which can result in relatively short tool life. Re-latively deep flutes also increase the tendency for hair-line cracks to develop during heat treatment. How2ver, if the flute is relatively shallow and the web is rela-tively thick, the web portion can absorb substantially more heat and, thus, substantially reduce the tendency for such cracks to develop during heat treatment and grinding of the flutes. A shallow flute is also desir-able from the standpoint of the cost of manufacture.It can be machined or ground in less time and results in proportionally greater -tool lifeO
Although not shown in the drawings, a majority of annular cutters require a center pilot pin or a center pilot drillO As a practical matter, the bore 88 in shank 14 for retaining the pilot pin or pilot drill has to be at least of a predetermined sizeO Thus, the inner diam-eter of the cutter has to be at least equal to the diameter of the pilot pin or pilot drill. Since the cutter of this invention has a web which can be thicker than the depth of ' 23.
the flute, it follows that with a pilot hole of predeter-mined size the outer diameter of a cutter according to the present invention can be less than the minimum prac~
tical outer diameter of a cutter constructed in accordance with the prior art.
Another advantage which flows from the fact that the present cutter has a thicker web section as com-pared with prior art cutters is that it can be made in two pieces, a tooth section and a body section, axially telescoped together in the web section and secured to one another by threads, welding, etc. The thicker web allows such telescopic connection without substantially affecting the strength of the cutter. A cutter of such two-piece construction has the obvious advantage of cost.
lS Onl~ the tooth section need be of expensive steelO
Furthermore, when the teeth become worn, only the tooth section need be replaced rather than the entire cutterO
A thicker web section also permits the forming of more teeth around the periphery of the cutter since it can withstand more torque and thrust. A greater number of teeth results in more cutting edges and faster cutting action.
24.
I have determined that from the standpoi.nt of maximum strength of the cutter in relation to the ease of ejection of the chips the thicXness of the web between successive teeth should be at least 55 to 60% o the thick-ness of the annular wall of the cutter. In the case ofcutters of the type illustrated in FIGS. 5 through 8 and FIG. 9 where each tooth is formed with four cutting edges, in the absence of special considerations, it is preferred to form the two inner cutting edges to about the same width and the two outer cutting edges to about the same width.
However, special consideration may dictate otherwise; or example, if it is desired to cut a very smooth surface on the central cylindrical slug, then the innermost cutting edge 34 should be substantially narrower than the next radially successive cutting edge 36. In any event, the wider of these two edges should not be wider than the depth of flute 22. on the other hand, i-f it is desired to cut an extremely smooth hole in a workpiece, then the outermost cutting edge 72 should be considerably narrower than the next radially successive cutting edge 70. If it is desired to cut both a smooth wall hole and a central - slug having a smooth side wall, then the innermost and outermost cutting edges should be narrower than the inter-mediate cutting edges. In any event, where the cutter is designed for cutting holes in steel and has at least four 3~
cutting edges, best results are normally obtained where the widest cutting edge has a width of not more than about .0625 inches. However, if increased rigidity is desired, this cutting edge width can be increased consid-erably by as much as two or three times.
Likewise, although it is preferred to form the crest between back-off faces 56,58 so that it intersects the outermost cutting edge, for certain applications the back-off faces may be ground so that the crest intersects one of the other cutting edges~ For example, if the cutter is being used to form a hole in two or more work-pieces which are stacked on one another, then the crest between the two back-off faces should lie very close to the inner periphery of the side wall of the cutter~ If the crest or the high point of the cutter is located closely adjacent the inner periphery of the cutter side wall, little difficulty is encountered in feeding the~
cutter through both of the overlying workpieces.
The high point of the cutter can be shifted to the inner cutting edge 34 without changing the location of crest 74. Since the back-off face 56 inclines upward-ly in a circumferential direction, it follows that if the shoulders 51,5~ are increased in length sufficiently, crest 74 will be spaced above, rather than below, edge 34.
In this case edge 34 will initiate the cutting action and 26.
3~
will penetrate through the uppermost workpiece before crest 74. Thus, if edge 34 is maintained at a very small width, the small lip remaining on the cut slug will not prevent it from moving up into the bore of the cutter so that the cutter can freely penetrate through the under-lying workpiece.
Since a chip tends to expand slightly immediate-ly after being cut, it is desirable to grind surface 28 of flute 22 so that the flute has its maximum radial depth at the junction of surfaces 28,32. This reduces to a minimum the frictional resistance of the chip cut by edge 38 against inner wall of the flute.
.
Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-An annular hole cutter comprising, a generally cylindrical annular side wall having a plurality of cutting teeth spaced circumferentially around the lower end thereof and having means for mounting the cutter on a rotary driving member; a plurality of flutes extending upwardly around the outer periphery of said annular wall from the lower end thereof; each tooth being connected with the next adjacent tooth by a circumferentially ex-tending web at the inner periphery of said annular wall, said webs being juxtaposed radially with said flutes;
each flute having circumferentially spaced and generally radially extending leading and trailing side walls and a circumferentially extending inner wall, said inner wall defining the radially outer side of said web; each tooth having a plurality of at least three radially extending cutting edges comprising a radially inner cutting edge, a radially intermediate cutting edge and at least one radially outer cutting edge, said inner and intermediate cutting edges on each tooth being formed on said web and disposed relative to one another such that each cuts a separate chip when the cutter is rotated and fed into a workpiece; said web being formed with a gullet means extending upwardly from the inner and intermediate cutting edges of each tooth and opening radially outwardly into the radially adjacent flute at their upper end; the outer cutting edge defining at least in part the lower end of the circumferentially trailing side wall of the adjacent flute; and each flute having a radial dimension not less than the radial dimension of the wider of the inner and intermediate cutting edges and a circumferential dimen-sion substantially greater than its radial dimension where-by, when the cutter is rotated and fed axially into a work-piece, the chips formed by the inner and intermediate cutting edges on the web portion of the cutter side wall are directed upwardly through their respective gullet means and into the radially adjacent flute.
2.
An annular cutter as called for in claim 1 wherein the cutting edges on each tooth are staggered circumferentially such that the radially outer end of the inner cutting edge is displaced forwardly in the direction of rotation of the cutter from the radially inner end of the intermediate cutting edge and the radially outer end of the intermediate cutting edge is displaced forwardly of the radially inner end of the outer cutting edge.
3.
An annular cutter as called for in claim 1 wherein said gullet means comprises a first gullet ex-tending upwardly from the inner cutting edge and a second gullet extending upwardly from the intermediate cutting edge.
4.
An annular cutter as called for in claim 3 wherein the upper end of each gullet inclines radially outwardly and axially upwardly.
5.
An annular cutter as called for in claim 1 wherein the radial depth of each flute is at least slight-ly greater than the thickness of said web.
6.
An annular cutter as called for in claim 1 wherein the thickness of said web is more than one-half the thickness of said annular wall.
7.
An annular cutter as called for in claim 1 wherein the thickness of the web is greater than the radial depth of the flute.
8.
An annular cutter as called for in claim 1 wherein the radial dimensions of the inner, intermediate and outer cutting edges are approximately equal.
9.
An annular cutter as called for in claim 1 wherein the radially inner cutting edge of each tooth is narrower than the remaining cutting edges.
10.
An annular cutter as called for in claim 1 wherein the outer cutting edge is narrower than the remaining cutting edges.
11.
An annular cutter as called for in claim 1 wherein the inner and outer cutting edges are narrower than the remaining cutting edges.
12.
An annular cutter as called for in claim 1 wherein the thickness of said web at its lower end is greater than one-half the thickness of said annular wall and the radial depth of the flute increases in an upwardly direction.
13.
An annular cutter as called for in claim 1 wherein the trailing side wall of each flute defines a smooth continuous spiral extending upwardly from the outer cutting edge.
14.
An annular cutter as called for in claim 1 wherein the two radially innermost cutting edges have a combined radial dimension not greater than the thick-ness of said web adjacent said cutting edges.
15.
An annular cutter as called for in claim 1 wherein the circumferential distance between the lead-ing and trailing side walls of each flute is maximum adjacent the upper end of the flute.
16.
An annular cutter as called for in claim 1 wherein each tooth is formed with four radially extend-ing cutting edges, the two outermost cutting edges de-fining the lower end of the trailing side wall portions of the adjacent flute.
17.
An annular cutter as called for in claim 16 wherein the thickness of each web is at least slightly greater than the radial depth of each flute.
18.
An annular cutter as called for in claim 17 wherein each cutting edge has a radial dimension of not more than about .0625 inches.
19.
An annular cutter as called for in claim 16 wherein the four cutting edges are circumferentially staggered progressively in the direction of rotation from the radially outer to the radially inner cutting edge.
20.
An annular cutter as called for in claim 19 wherein the radially outermost cutting edge is stagger-ed only slightly from the radially next adjacent cutting edge such that the two outermost cutting edges cut a single chip.
21.
An annular cutter as called for in claim 19 wherein the two outermost cutting edges are staggered sufficiently so that each cuts a separate chip.
22.
An annular cutter as called for in claim 21 wherein the outermost cutting edge is formed at the lower end of the gullet which opens at its upper end into said flute, said gullet having a vertical extent which is not substantially greater than said first-mentioned gullet means.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-An annular hole cutter comprising, a generally cylindrical annular side wall having a plurality of cutting teeth spaced circumferentially around the lower end thereof and having means for mounting the cutter on a rotary driving member; a plurality of flutes extending upwardly around the outer periphery of said annular wall from the lower end thereof; each tooth being connected with the next adjacent tooth by a circumferentially ex-tending web at the inner periphery of said annular wall, said webs being juxtaposed radially with said flutes;
each flute having circumferentially spaced and generally radially extending leading and trailing side walls and a circumferentially extending inner wall, said inner wall defining the radially outer side of said web; each tooth having a plurality of at least three radially extending cutting edges comprising a radially inner cutting edge, a radially intermediate cutting edge and at least one radially outer cutting edge, said inner and intermediate cutting edges on each tooth being formed on said web and disposed relative to one another such that each cuts a separate chip when the cutter is rotated and fed into a workpiece; said web being formed with a gullet means extending upwardly from the inner and intermediate cutting edges of each tooth and opening radially outwardly into the radially adjacent flute at their upper end; the outer cutting edge defining at least in part the lower end of the circumferentially trailing side wall of the adjacent flute; and each flute having a radial dimension not less than the radial dimension of the wider of the inner and intermediate cutting edges and a circumferential dimen-sion substantially greater than its radial dimension where-by, when the cutter is rotated and fed axially into a work-piece, the chips formed by the inner and intermediate cutting edges on the web portion of the cutter side wall are directed upwardly through their respective gullet means and into the radially adjacent flute.
2.
An annular cutter as called for in claim 1 wherein the cutting edges on each tooth are staggered circumferentially such that the radially outer end of the inner cutting edge is displaced forwardly in the direction of rotation of the cutter from the radially inner end of the intermediate cutting edge and the radially outer end of the intermediate cutting edge is displaced forwardly of the radially inner end of the outer cutting edge.
3.
An annular cutter as called for in claim 1 wherein said gullet means comprises a first gullet ex-tending upwardly from the inner cutting edge and a second gullet extending upwardly from the intermediate cutting edge.
4.
An annular cutter as called for in claim 3 wherein the upper end of each gullet inclines radially outwardly and axially upwardly.
5.
An annular cutter as called for in claim 1 wherein the radial depth of each flute is at least slight-ly greater than the thickness of said web.
6.
An annular cutter as called for in claim 1 wherein the thickness of said web is more than one-half the thickness of said annular wall.
7.
An annular cutter as called for in claim 1 wherein the thickness of the web is greater than the radial depth of the flute.
8.
An annular cutter as called for in claim 1 wherein the radial dimensions of the inner, intermediate and outer cutting edges are approximately equal.
9.
An annular cutter as called for in claim 1 wherein the radially inner cutting edge of each tooth is narrower than the remaining cutting edges.
10.
An annular cutter as called for in claim 1 wherein the outer cutting edge is narrower than the remaining cutting edges.
11.
An annular cutter as called for in claim 1 wherein the inner and outer cutting edges are narrower than the remaining cutting edges.
12.
An annular cutter as called for in claim 1 wherein the thickness of said web at its lower end is greater than one-half the thickness of said annular wall and the radial depth of the flute increases in an upwardly direction.
13.
An annular cutter as called for in claim 1 wherein the trailing side wall of each flute defines a smooth continuous spiral extending upwardly from the outer cutting edge.
14.
An annular cutter as called for in claim 1 wherein the two radially innermost cutting edges have a combined radial dimension not greater than the thick-ness of said web adjacent said cutting edges.
15.
An annular cutter as called for in claim 1 wherein the circumferential distance between the lead-ing and trailing side walls of each flute is maximum adjacent the upper end of the flute.
16.
An annular cutter as called for in claim 1 wherein each tooth is formed with four radially extend-ing cutting edges, the two outermost cutting edges de-fining the lower end of the trailing side wall portions of the adjacent flute.
17.
An annular cutter as called for in claim 16 wherein the thickness of each web is at least slightly greater than the radial depth of each flute.
18.
An annular cutter as called for in claim 17 wherein each cutting edge has a radial dimension of not more than about .0625 inches.
19.
An annular cutter as called for in claim 16 wherein the four cutting edges are circumferentially staggered progressively in the direction of rotation from the radially outer to the radially inner cutting edge.
20.
An annular cutter as called for in claim 19 wherein the radially outermost cutting edge is stagger-ed only slightly from the radially next adjacent cutting edge such that the two outermost cutting edges cut a single chip.
21.
An annular cutter as called for in claim 19 wherein the two outermost cutting edges are staggered sufficiently so that each cuts a separate chip.
22.
An annular cutter as called for in claim 21 wherein the outermost cutting edge is formed at the lower end of the gullet which opens at its upper end into said flute, said gullet having a vertical extent which is not substantially greater than said first-mentioned gullet means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17095980A | 1980-07-21 | 1980-07-21 | |
| US06/170,959 | 1980-07-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1150536A true CA1150536A (en) | 1983-07-26 |
Family
ID=22621982
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000375298A Expired CA1150536A (en) | 1980-07-21 | 1981-04-13 | Annular hole cutter |
Country Status (19)
| Country | Link |
|---|---|
| JP (1) | JPS5940570B2 (en) |
| AR (1) | AR223120A1 (en) |
| AU (1) | AU541273B2 (en) |
| BE (1) | BE888838A (en) |
| BR (1) | BR8103193A (en) |
| CA (1) | CA1150536A (en) |
| CH (1) | CH643168A5 (en) |
| DE (1) | DE3118579A1 (en) |
| ES (1) | ES8203250A1 (en) |
| FR (1) | FR2486842B1 (en) |
| GB (1) | GB2080162B (en) |
| IL (1) | IL62677A (en) |
| IT (1) | IT1142432B (en) |
| MX (1) | MX152082A (en) |
| NL (1) | NL182456C (en) |
| NO (1) | NO151850C (en) |
| NZ (1) | NZ196954A (en) |
| SE (1) | SE449060B (en) |
| ZA (1) | ZA812715B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GR77678B (en) * | 1981-09-21 | 1984-09-25 | Hougen Everett D | |
| CA1190419A (en) * | 1981-09-21 | 1985-07-16 | Everett D. Hougen | Annular cutter |
| US4952102A (en) * | 1982-09-27 | 1990-08-28 | Hougen Everett D | Annular hole cutter |
| US5145296A (en) * | 1982-09-27 | 1992-09-08 | Hougen Everett D | Apparatus and method for cutting holes |
| IL69696A (en) * | 1982-09-27 | 1987-12-20 | Hougen Everett D | Annular hole cutter |
| US4813819A (en) * | 1982-09-27 | 1989-03-21 | Hougen Everett D | Method for cutting holes |
| GB2137126A (en) * | 1982-10-19 | 1984-10-03 | Talbot & Co Ltd F W | Trepanning Cutter |
| USRE33598E (en) * | 1986-01-16 | 1991-05-28 | Walker-Hagou B.V. | Facing cutter |
| ATE54852T1 (en) * | 1986-01-16 | 1990-08-15 | Walker Hagou Bv | FLAT CUTTER. |
| US5049010A (en) * | 1988-08-04 | 1991-09-17 | Unibit Corporation | Metal cutting tool |
| US5074722A (en) * | 1991-03-15 | 1991-12-24 | Greenlee Textron Inc. | Hole cutter |
| TWI263552B (en) * | 2003-06-05 | 2006-10-11 | Miyanaga Kk | Core cutter |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US28416A (en) * | 1860-05-22 | Improvement in plows | ||
| USRE28416E (en) * | 1971-12-29 | 1975-05-06 | Annular hole cutter | |
| BE788401A (en) * | 1971-12-29 | 1973-03-05 | Hougen Everett D | ROTARY CUTTING TOOL |
| US3860354A (en) * | 1971-12-29 | 1975-01-14 | Everett D Hougen | Annular hole cutter |
| SE381592B (en) * | 1975-01-20 | 1975-12-15 | Sandvik Ab | DRILLING TOOLS |
-
1981
- 1981-04-13 CA CA000375298A patent/CA1150536A/en not_active Expired
- 1981-04-16 GB GB8112151A patent/GB2080162B/en not_active Expired
- 1981-04-16 SE SE8102461A patent/SE449060B/en not_active IP Right Cessation
- 1981-04-17 IL IL62677A patent/IL62677A/en unknown
- 1981-04-21 NO NO811353A patent/NO151850C/en unknown
- 1981-04-24 MX MX187011A patent/MX152082A/en unknown
- 1981-04-24 AU AU69839/81A patent/AU541273B2/en not_active Ceased
- 1981-04-24 ZA ZA00812715A patent/ZA812715B/en unknown
- 1981-04-27 NL NLAANVRAGE8102057,A patent/NL182456C/en not_active IP Right Cessation
- 1981-04-28 NZ NZ196954A patent/NZ196954A/en unknown
- 1981-05-07 IT IT48418/81A patent/IT1142432B/en active
- 1981-05-08 JP JP56068471A patent/JPS5940570B2/en not_active Expired
- 1981-05-11 DE DE19813118579 patent/DE3118579A1/en active Granted
- 1981-05-14 AR AR285317A patent/AR223120A1/en active
- 1981-05-18 BE BE0/204815A patent/BE888838A/en not_active IP Right Cessation
- 1981-05-19 FR FR8109946A patent/FR2486842B1/en not_active Expired
- 1981-05-22 BR BR8103193A patent/BR8103193A/en not_active IP Right Cessation
- 1981-05-22 CH CH334881A patent/CH643168A5/en not_active IP Right Cessation
- 1981-06-02 ES ES502680A patent/ES8203250A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| IL62677A0 (en) | 1981-06-29 |
| BE888838A (en) | 1981-09-16 |
| IT8148418A0 (en) | 1981-05-07 |
| FR2486842B1 (en) | 1986-04-04 |
| JPS5940570B2 (en) | 1984-10-01 |
| FR2486842A1 (en) | 1982-01-22 |
| GB2080162A (en) | 1982-02-03 |
| CH643168A5 (en) | 1984-05-30 |
| NL182456C (en) | 1988-03-16 |
| ES502680A0 (en) | 1982-04-01 |
| SE8102461L (en) | 1982-01-22 |
| NO811353L (en) | 1982-01-22 |
| NZ196954A (en) | 1984-12-14 |
| ES8203250A1 (en) | 1982-04-01 |
| NL8102057A (en) | 1982-02-16 |
| ZA812715B (en) | 1982-08-25 |
| NO151850B (en) | 1985-03-11 |
| IT1142432B (en) | 1986-10-08 |
| NO151850C (en) | 1985-06-19 |
| DE3118579C2 (en) | 1989-03-23 |
| DE3118579A1 (en) | 1982-06-24 |
| MX152082A (en) | 1985-05-28 |
| NL182456B (en) | 1987-10-16 |
| GB2080162B (en) | 1984-08-30 |
| SE449060B (en) | 1987-04-06 |
| BR8103193A (en) | 1982-08-24 |
| AU541273B2 (en) | 1985-01-03 |
| AU6983981A (en) | 1982-01-28 |
| JPS5727608A (en) | 1982-02-15 |
| AR223120A1 (en) | 1981-07-15 |
| IL62677A (en) | 1984-05-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |