CA1220059A - Two-prong rotary bit, especially for use with roof drills, and insert therefor - Google Patents
Two-prong rotary bit, especially for use with roof drills, and insert thereforInfo
- Publication number
- CA1220059A CA1220059A CA000461321A CA461321A CA1220059A CA 1220059 A CA1220059 A CA 1220059A CA 000461321 A CA000461321 A CA 000461321A CA 461321 A CA461321 A CA 461321A CA 1220059 A CA1220059 A CA 1220059A
- Authority
- CA
- Canada
- Prior art keywords
- bit
- face
- inserts
- cutting edges
- degrees
- 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
- 239000011435 rock Substances 0.000 description 19
- 238000005553 drilling Methods 0.000 description 11
- 230000035515 penetration Effects 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 241000343235 Maso Species 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000010008 shearing Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 239000010438 granite Substances 0.000 description 1
- 231100000206 health hazard Toxicity 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/60—Drill bits characterised by conduits or nozzles for drilling fluids
- E21B10/602—Drill bits characterised by conduits or nozzles for drilling fluids the bit being a rotary drag type bit with blades
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
- E21B10/54—Drill bits characterised by wear resisting parts, e.g. diamond inserts the bit being of the rotary drag type, e.g. fork-type bits
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
- E21B10/58—Chisel-type inserts
Landscapes
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Drilling Tools (AREA)
- Earth Drilling (AREA)
- Processing Of Stones Or Stones Resemblance Materials (AREA)
Abstract
TITLE OF THE INVENTION
A TWO-PRONG ROTARY BIT, ESPECIALLY FOR USE WITH ROOF
DRILLS, AND INSERT THEREFOR
ABSTRACT OF THE DISCLOSURE
Disclosed according to the present invention is a two-prong rotary drill bit, especially for use with roof drills. The two-prong bit has a supporting body having an axis of rotation. The two-prong bit has a pair of inserts, one insert on each of the prongs. Each of the inserts has a cutting portion facing in the direction of rotation and a mounting portion. When viewed in a direction parallel to the axis of rotation, each of the inserts will have a cross sectional configuration which is generally wedge-shaped. Also disclosed are wedge shaped inserts especially for use with roof drill bits.
A TWO-PRONG ROTARY BIT, ESPECIALLY FOR USE WITH ROOF
DRILLS, AND INSERT THEREFOR
ABSTRACT OF THE DISCLOSURE
Disclosed according to the present invention is a two-prong rotary drill bit, especially for use with roof drills. The two-prong bit has a supporting body having an axis of rotation. The two-prong bit has a pair of inserts, one insert on each of the prongs. Each of the inserts has a cutting portion facing in the direction of rotation and a mounting portion. When viewed in a direction parallel to the axis of rotation, each of the inserts will have a cross sectional configuration which is generally wedge-shaped. Also disclosed are wedge shaped inserts especially for use with roof drill bits.
Description
BAC~GRQUtaD o~ ~E I~
p~ v~t~o~ t~ ~o ~g~
~oole an~ }or~ par~ rly~ ~elat~$ ~o ~ f dr111 bit~
for ~ ln coal ~in~.
~ a~l~, ~e ~ en~ n~ n re~
t~o-pre~n~ " ce~ter ~cuum rc~ dr~ll bl~
Roof d~ re ~ d or dr~ g 1~ole~
~~ ~ a~nder~ A~ 8., ~ r th~
dr~ d" ~:he drlll i~ ~e~ea a~n~l ~n a~cbor 1~ ~38 10 ln ~ hole as ~n ~ld ~n ~upporSlng th~ e roo~O
Under cert~in condie~on~ a ro~f drlll b~t ~e $e~eC~:Q
~hl~h ~n ~ u~ed ln c~n~uncUo~ h a ~ae~ y~
~hen the u~a ~y~e~ o~er rougb ~he ente~
t~e b~ called a center ~actau~ bà~ ~h~le p~Irp~
~5 o the va~u~ ~ys~ce~ is to colïect ~be ~ne p~r~icle~
gen~rated æ~rinq the dr~lin~ of ~e ~ole~ ~ben ~1~
¢~nter ~cuu~ rc~of drlll ~e ~c~ ~or~ u~t be re~ ced .
The center vacuum roof drill bit which has been the standard in the coal mining industry for a number of years is illustratedO This drill bit can be generally described as an insert brazed ~o a supporting body wherein the insert comprises a flat piece of hard, wear resistant material (usually cemented carbide)O The hard insert has a zero degrees rake angle and a continuous cutting edge profile extending diametrically across the roof 2S drill bito
p~ v~t~o~ t~ ~o ~g~
~oole an~ }or~ par~ rly~ ~elat~$ ~o ~ f dr111 bit~
for ~ ln coal ~in~.
~ a~l~, ~e ~ en~ n~ n re~
t~o-pre~n~ " ce~ter ~cuum rc~ dr~ll bl~
Roof d~ re ~ d or dr~ g 1~ole~
~~ ~ a~nder~ A~ 8., ~ r th~
dr~ d" ~:he drlll i~ ~e~ea a~n~l ~n a~cbor 1~ ~38 10 ln ~ hole as ~n ~ld ~n ~upporSlng th~ e roo~O
Under cert~in condie~on~ a ro~f drlll b~t ~e $e~eC~:Q
~hl~h ~n ~ u~ed ln c~n~uncUo~ h a ~ae~ y~
~hen the u~a ~y~e~ o~er rougb ~he ente~
t~e b~ called a center ~actau~ bà~ ~h~le p~Irp~
~5 o the va~u~ ~ys~ce~ is to colïect ~be ~ne p~r~icle~
gen~rated æ~rinq the dr~lin~ of ~e ~ole~ ~ben ~1~
¢~nter ~cuu~ rc~of drlll ~e ~c~ ~or~ u~t be re~ ced .
The center vacuum roof drill bit which has been the standard in the coal mining industry for a number of years is illustratedO This drill bit can be generally described as an insert brazed ~o a supporting body wherein the insert comprises a flat piece of hard, wear resistant material (usually cemented carbide)O The hard insert has a zero degrees rake angle and a continuous cutting edge profile extending diametrically across the roof 2S drill bito
-2--There are a number of long~standing problems with this prior art roof drill bit. A distinct disadvantage of a continuous cutting edge profile is the lack of cutting speed in the center of rotation, thereby requiring higher thrust at this point to penetrate ~he rock, The higher thrust required may cause the bi~ to fail, especially when drilling in hard rock formations.
Another prob7em with ~he prior art roof drill bit is the cutting action of the bit. The prior art roof drill bit proceeds through the rock by first primarily crushing the rock, then penetrating into the crushed rock and finally shearing the rock. This type of action requires a high thrust with a concomitant increase in wear of the hard, wear resistant material. Typically, the prior art roof drîll bit is replaced after only one pass.
A further problem with the prior art roof drill bit is the generation o very fine dust particles, which causes the vacuum system to work harder than iæ
necessary. Those particles which escape the vacuum system become a health hazard to those in the mine.
Th~ applicant of the present invention is familiar with another type of rotary drill bit which is illus-trated in U.S.S.R. Inven~or's Certificate No. 395271.
The present applicant is a coinventor of the drill bit disclosed in this document. The rotary drill bit illus-trated in this Inventor's Certificate was also the subject of a paper authored by the applican~ This paper was entitled "Hand-~eld Power Tools for Drilling Small Diameter Holes in Conskruction Materials,"
Industrial C~nstru~tion a~d En~ineerin~ Structures .____ gazine, Kiev (USSR), Volume l (1975).
The rotary drill bits illustra~ed in the Inventorls Certificate and in the paper are masonry drill bits for drilling in concrete, brick or other similar construG-tion materials with a hand-held electric drill. These masonry drill bits are tipped with wedge-shaped inserts.
A comparison of the operating conditions of masonry drill bits and roof drill bi~s illustrates ~he fact that the suitability of a drill bit for use as a masonry drill bit will not necessarily indicate that this same drill bit is suitable for use as a roof drill bit4 The comparison of maso~ry and roof drill bit operating conditions is as followso .
~ - Maso~ Blt. Roof Blt_ Cutting Diameter .. Inches ~. ~5`o.r 1~sa . . I.~r more Th-rust, ~ -.Sp.eed, rpm . ~ .~ 7.00-lOOU 250 .
.Po,wer ~t Motor.,.~.P . . 25-.~S. . . 3-S _.
Torque, Foo.t-Pounds . ..1.3-2~5 . ,~ 60-8.0 It is immediately obvious from this comparison that the thrust) power and torque for the respective masonry and roof drill bits differ by orders of magnitude~
Accordingly~ it is an object of the invention to have a roof drill bit, and insert therefor, without any of the disadvantages of the prior art roof drill bitso ~t ~ ~no~ ~ ~h~ ~Y~n~
dr i 11 ~ an~ ef~ h~ Y
~p~ n ~t~en~-h ~n~ n~ hlpp~
r~c:tu~i~g.
It ~ othe1r ob~c~ ~ ~e ~ven~g~on ~ca ha~e ~
s~er ~ l~e~ u~ le~ an~3 s~~er le~ ~e~r ~:b~a ~h~ prl~r ~ U6e of ~r~
~t 1~ o~ Qtlo~
a roof drill b~ nd In~er~ ~herefor econQ~ a~ a~u~ ~nd ~o~ e~ e ~
l~is~lo~ed ~c¢ord~ng ~o ~h~ ln~en~ D ~ rong rota~ b~k, espeel~lly or o~e wl~ roof drlll~
15 b~ co~prlse~ a ~upFort~ng body haYing ~n ~ of rota-tlcn and R p~ir ~ ln~ert~. ~ach of t~e ~n~er~ a~
cuttin~ portlo~ ~c~n~ in ~he dl~ectlo~ of r~3t~tlo ms)un'c~D~ port~on an~ hen ~ ed iL~ ~ ~ir~ctlo~
parallel eo ~he a~s ~f ro~atlora, ~ cro~ ~ec~lo~l 20 on~îgur~tlon ~hi~ y~n~r~ ed~çe ~h~
The advantages or this two-prong bit over the prior art bit are many. One advantage of the two-prong bit is that it is s~ronger due to the wedge shape of the inserts~ Another advantage of the two-prong bit is the way it proceeds through the rockO
X5 The two-prong bit proceeds through the rock by first, fracturing and crushing the rock, then penetrating the 0~
~2~5~
fractured and crushed rockf and finally shearing the rock.
As a result of this cu~ting action, there is lower thrust and, consequently, lower wear of the inser~s.
Due to the lower wear of the inserts, there is also less friction generated during a drilling process so ~hat the drill can be operated at higher drilling speeds.
In contrast, the prior art drill bit as explained earlier crushes the ro~k, penetrates through the crushed rock and then shears the rock. Because it takes more energy to crush rock than to fracture it, this type of action requires higher thrust and higher wear on each of the inserts which will then generate more friction. As a consequence, the prior art drill bit has to be operated at a lower drillin~ speedO
Also disclo~ed as a separate article of commerce is an insert especially for use with a roof drill bit.
This insert comprises a generally wedge-shaped body.
I'here are two planar front faces tapering toward each other and intersecting so as to form a face cutting edge. Opposite to the face cutting edge the two planar front faces diverge and terminate in a mounting portion.
The insert also comprises a clearance face and a support face angularly related to and separated by the face cutting edge~ the clearance face intersecting the front faces so as to form two main cutting edges. The clear ance face also intersects the mounting portion.
Fi.nally, the face cutting edge and the two main cutting edges coincide in a common apexO
The apex of the wedge~shaped insert is an important feature of the invention since it has been proven to be effective in fracturing the rock, instead of crushing the rock as was the case with the prior art drill bit~
~RIEF ~ NGS:
The exact nature of the present invention will become more clearly apparent upcn reference to the following detailed specification taken in connection with the accompanying drawings in which:
Figure 1 is a perspective view of a prior art drill bit.
Figure 2 is a front view of the drill bit according to the invention.
Figure 3 is the drill bit of Figure 2 rotated 90 degrees.
Figure 4 is a plan view of the drill bit of Figur~s 2 and 3.
Figure 5 is an enlarged plan view of the inserts shown with the drill bit of Figures 2 to 4.
Figure 6 is a frontal view of another embodiment of a drill bit according to the invention.
Figure 7 is the drill bit of Figure 6 rotated 90 degrees.
Figure 8 is a plan view of the drill bit of Figures 6 and 7.
Figure 9 is an enlarged plan view of the inserts shown with the drill bit of Figures 6 to 8~
Figure 10 is an enlaryement of the plan view of the inse~t shown in Figure 9.
pETAILED _E CRIPTIO~ O~ T~E VENTION:
Referring to the drawings in more detail, and specifically referring to Figures 2 to 5, disc].osed according ~o the invention is a two-prong bit 12, especially for use with a roof drill ~not shown). ThP
bit comprises a supporting body 14 having an axis of rotation 16. There is a pair of inserts 18 r each of the inserts 18 having a cutting portion 20 facing in the direction of rotation 22, a mounting portion 24 and, when viewed in a direction parallel to the axis of rotation 16, a cross sectional configuration which is generally w~dge shaped.
In operation, one end lS of the supporting body would be attached to the roof drill. End 15 would typically have an hexagonal cross section, as is partially shown at 17 in Figure 4 for connection with a similar hexagonal configuration on the roof drill.
The cutting portion 20 of each of the inserts 18 comprises two planar front faces 26 extending ~orwardly in the rotational sense and axially so as to intersect each other and a clearance face 28. With reerence to Figure 4, the direction of rotation is shown at 22, and it can be seen that the cutting portion of each o~ the inserts faces and rotates in the direction of rotation.
~2~5~
The intersection of the planar front faces forms a face cutting edge 30 at the forwardmost part of the insert.
Further, ~he intersection of each of the planar front faces 26 with the clearance face 28 forms two main cutting edges 32. The face cutt.ing edge 30 and two ma.in cutting edges 32 coincide in a common apex 34~ The nature of the apex 34 is most clearly shown in Figures 2 and 3. Due to the pointed or nearly pointed nature of the apex, the rock is easily fractured.
The cutting portion 20 of each of the inserts 18 further comprises two lateral cutting edges 36, 38 formed by the intersection of the two planar front faces 26 and the mounting portion 24. One o the lateral cutting edges 36 or 38 is an inner lateral cutting edge 36 and the other lateral cutting edge i5 an outer lateral cutting edge 38.
As best seen in Figures 4 and 5, the mounting portion 24 is curvilinear when viewed parallel to the axis of rotation 16. In a pre~erred embodiment, the mounting portion is cylindrical as can also be seen in Figure 2.
Preferably, the dihedral angle 40, as best seen in Figure 5, between the two planar front faces, is 90 to 100 degrees. As best seen in Figure 3, it is preferable for each of the inserts that the clearance angle 42 is 15 to 20 degrees r the rake angle 43 is -10 to -20 degrees, and the included angle 44 between the face ~9--5~
cutting edge 30 and the clearance face 28 is 70 to 90 degrees~
It has been found that the strength of the i~sert is enhanced when the dihedral angle is 90 to 100 degrees and the included angle between the face cutting edge and the clearance face is 70 to 90 degrees. The insert will be the stronges~ when the dihedral angle 40 is 100 degrees and the included angle 44 is 90 degrees.
It has also been found ~hat thrust requirements are minimized when the clearance angle 42 is 15 to 20 degrees and the rake angle 43 is -10 to -20 degrees.
At each of the lateral cutting edges 36, 3~, the angle 46, as best seen in Figure 5, between the planar front face 26 and a plane 48 tangent to the mounting ]5 portion 24 is 90 degrees~ Constructing the insert so that the mounting portion intersects with the planar ~ront ~ace at an angle of 90 degrees is important for two reasons. The first is that the insert is made stronger and the second reason is that the lateral cutting edge is sharper.
The drill bit 12 has an outside diameter 50, as measured between the respective outer lateral cutting edges, and an inside diameter 52, as measured between the respective inner lateral cutting edges. This is best seen in Figures 2 and 4. It is preferred that the outside diameter is about five times greater than th~
inside diameter. When the ratio of the outside to inside diameter is held at about five, it is insured that the central portion of the hole not cut by the inserts is not so large as to prevent further movement o~ the drill bit in~o ~he hole. At the same time, if the ratio of the outside diame~er to the inside diameter is much greater than five, thrust re~uirements would be increased. Preferably, the ratio of the outside diameter to the inside diameter should be in the range of ~.7 ~o 5.2.
When the bit is viewed parallel to the axis o~
rotation 16, a first line 54 passing through the inner and outer lateral cutting edges of one of the inserts will be parallel with a second line 56 passing through the inner and outer lateral cutting edges of the other insert. Preferably, the first 54 and second 56 lines are forward in the rotational sense with respect to a diametric line 58 which is perpendicular to the rota-tional axis 16 of the bit~ By staggering the inserts with respect to the diametric line 58 as is done in the preferred embodiment, it is believed that thrust reyuirements will be reduced.
In one embodiment of the drill bit, the main 32 and ~ace cutting edges 30 are rectilinear.
The central portion 21 of the supporting body 14 is beefed up so as to strengthen the body. Additionally, the top of the central portion 21 has sloping faces 23 which slope away from the center of the body. Slopin~
faces 23 assist in the removal of the cut rock.
5~
In another embodiment of the drill bit, as shown in Figures 6 through 10, the two main cutting edges 32 are rectilinear and the face cutting edg~ 60 is cylindrical.
The cylindrical nature of the face cu~ting edge is best seen in ~igures 8 through 10.
It has been found that the wedge--shaped insert is suitable for drilling in soft rock as well as in very hard rocX; however, it has also been found that, when drilling in very hard rock, it is best that the ~ace cutting edge 60 have a cylindrical shape. The cylin-drical shape assists in, first, strengthening the insert and, second, preventing the insert from chipping.
In all other respects, the drill bit of Figures 6 through 10 is equivalent to the drill bit of Figures through 5O
Referring again to the drill bit of Figures 6 through 10, and specifically referring to Figure 10, the radius 62 of the cylindrical mounting portion 24 is R
and the radius 64 of the cylindrical cutting edge 60 is .5 to .707R when the dihedral angle 70 between the two front faces is 90 degrees. When the dihedral angle between the two planar front faces is 10~ degrees, then the radius 62 of the cylindrical mounting portion would be R and the radius 66 of the cylindrical cutting edge 70 would be .5 to .643R.
The radius R of the cylindrical mounting portion is measured from point 61 which is the intersection of the extensions of planar front faces 26. In our experience, the values of R will range from about .29 inches for a one inch diameter drill bit to about .43 inches for a one and one-half inch diameter drill bit.
Disclosed also as a separate article of commerce is S an insert 18 especially for use with a roof drill bit 12.
Referring specifically now to Figures 2 through 5, the insert has a generally wedge-shaped bodv. Two planar front faces 26 taper ~oward each other and inter-sect so as to form a face cutting edge 30. Opposite to the face cutting edge, the two planar front faces diverge and terminate in a mounting portion 24. There i.s also a clearance face 28 and a support face 68 angularly related to and separated by the face cutting edge 30. As seen best in Figure 3, the clearance face and support face form the top and bottom, respectively, of the insert. While the clearance ~ac~ and the support face may be parallel, it is not necessary to achieve the objects of the invention that they be parallel and~ in fact, as shown in Figure 3, they are not parallel. The clearance face 28 intersects the front faces 26 so as to form two main cutting edges 32. The clearance face 28 also intersects the mounting portion 24. The face cutting edge 30 and two main cutting edges 32 coincide in a common apex 34.
The insert further comprises two lateral cutting edges 36, 38 formed by the intersection of the two planar front faces 26 and the mounting portion 24.
The mounting portion, as best seen in Figures 4 and 5, is curvilinear when viewed from the clearance face.
It is preferred that the mounting portion be cylindrical as seen in Figure 2.
S Preferably, the dihedral angle 4n between the two planar front faces 26 is 90 to 100 degrees, and included angle 44 between ~he face cut~ing edge 30 and the cl~ar-ance face 28 is 70 to 90 degrees. For the ultimate in insert strength, it is most preferred that the dihedral angle 40 be 100 degrees and the included angle 44 be 90 degrees.
It is also preferable tha~ at each of the lateral cutting edges 36, 38, the angle 46 between the planar front face 26 and a plane 48 tangent to the mounting portion ~4 be 90 degrees.
In the emhodiment of the insert as shown in Figures 2 to 5, the main 32 and face 30 cutting edges are recti-linear.
Referring now to Fîgures 6 through 10, another ~0 embodiment of the insert according to the present inven-tion is shown. In all respects, the insert shown in Figures 6 to 10 is similar to the insert seen in Figures 2 to 5 except that the face cutting edge 60 is cylindri-cal instead of rectilinear.
It is preferred that when the dihedral angle 70 between the two planar front faces is 90 degrees and the radius 62 of the cylindrical mounting portion is R, then the radius 64 of the cylindrical cutting edge 60 is .5 to .707R. When ~he dihedral angle 72 between the two planar front faces is 100 degrees, then the radius 6~ of the cylindrical face cutting edge 60 is .5 to .643R.
This is best shown în Figure 10.
5 TEST: RESULTS:
Applicant has undertaken comparative performance testing between the prior art standard center vacuum bit as shown in Figure 1, and a wedge-shaped inserted bit according to this invention~ In Table 1, the bit geometry is described for each of the standard bit and the wedge-shaped inserted bit.
Each of the drill bits was drilled into a sample uf Barre granite, which is a hard ype of rock. The tes~s began by starting approximately at the same initial thrust. The operator of the drilling rig would then attempt to maintain a constant penetration rate for earh of the drill bits. When the penetration rate began to decrease, thrust would be increased. Penetration rate and thrust were constantly monitored. After the test hole of about 28 inches in length was completed, the thrust at completion ~maximum thrust) was noted. The drill bits were then removed from the drilling rig and examined for wear. Finally, specific wear ~width of wear land per feet of hole drilled~ for the drill bits was calculated.
Table 2 shows results of the testing.
Even though an attempt was made to maintain a constant penetration rate for both types of bits, the standard bit fell behind the wedge-shapecl inserted bit, notwithstanding th~ increased amount of t:hrust applied.
I~ should be noted that the maximum thrust of 7497 pounds applied to the s~andard bit is close to the critical thrust load at which point sufficient heat due to friction will be generated that the hardness of the cemented carbide will begin to decrease If this critical thrust load is maintained for any length of kime, the drill bit will self-destruct.
Most noteworthy of the test results is the compara-tive wear of the bits. The standard bit exhibited over one hundred percent more specific wear than the wedge-shaped inserted bit~
Several conclusions can be drawn from the results in Table 2. Overall, the wedge-shaped inser~ed bit performed much better than the standard bit. The wedge-shaped inserted bit can drill faster and at lower thrust levels a~d sufEers less wear than the standard bit~
Ultimately, by drilling at lower thrust levels, there is less chance that the insert will break, and by drilling with less wear, this means that the bit can be used for longer periods of time and so will be cost effective.
T~BLE 1 Insert ShapeStandard Wçdged Bit Geometry Rake Angle 0 -10 Clearance Angle 20 15 Included Angle 70 85 Dihedral Angle - 98 ~T~B4E
Insert ShapeS~andar~
Initial Thrust, lbs. 1536 1700 Average Thrust, lbs. 56S5 4409 Maximum Thrust, lbs. 7497 6116 Penetration Rate, In./Min. 10.7 12.6 Specific Wear, In./Ft. .079 .036 Modifications may ~e made within the scope of the appended claims.
Another prob7em with ~he prior art roof drill bit is the cutting action of the bit. The prior art roof drill bit proceeds through the rock by first primarily crushing the rock, then penetrating into the crushed rock and finally shearing the rock. This type of action requires a high thrust with a concomitant increase in wear of the hard, wear resistant material. Typically, the prior art roof drîll bit is replaced after only one pass.
A further problem with the prior art roof drill bit is the generation o very fine dust particles, which causes the vacuum system to work harder than iæ
necessary. Those particles which escape the vacuum system become a health hazard to those in the mine.
Th~ applicant of the present invention is familiar with another type of rotary drill bit which is illus-trated in U.S.S.R. Inven~or's Certificate No. 395271.
The present applicant is a coinventor of the drill bit disclosed in this document. The rotary drill bit illus-trated in this Inventor's Certificate was also the subject of a paper authored by the applican~ This paper was entitled "Hand-~eld Power Tools for Drilling Small Diameter Holes in Conskruction Materials,"
Industrial C~nstru~tion a~d En~ineerin~ Structures .____ gazine, Kiev (USSR), Volume l (1975).
The rotary drill bits illustra~ed in the Inventorls Certificate and in the paper are masonry drill bits for drilling in concrete, brick or other similar construG-tion materials with a hand-held electric drill. These masonry drill bits are tipped with wedge-shaped inserts.
A comparison of the operating conditions of masonry drill bits and roof drill bi~s illustrates ~he fact that the suitability of a drill bit for use as a masonry drill bit will not necessarily indicate that this same drill bit is suitable for use as a roof drill bit4 The comparison of maso~ry and roof drill bit operating conditions is as followso .
~ - Maso~ Blt. Roof Blt_ Cutting Diameter .. Inches ~. ~5`o.r 1~sa . . I.~r more Th-rust, ~ -.Sp.eed, rpm . ~ .~ 7.00-lOOU 250 .
.Po,wer ~t Motor.,.~.P . . 25-.~S. . . 3-S _.
Torque, Foo.t-Pounds . ..1.3-2~5 . ,~ 60-8.0 It is immediately obvious from this comparison that the thrust) power and torque for the respective masonry and roof drill bits differ by orders of magnitude~
Accordingly~ it is an object of the invention to have a roof drill bit, and insert therefor, without any of the disadvantages of the prior art roof drill bitso ~t ~ ~no~ ~ ~h~ ~Y~n~
dr i 11 ~ an~ ef~ h~ Y
~p~ n ~t~en~-h ~n~ n~ hlpp~
r~c:tu~i~g.
It ~ othe1r ob~c~ ~ ~e ~ven~g~on ~ca ha~e ~
s~er ~ l~e~ u~ le~ an~3 s~~er le~ ~e~r ~:b~a ~h~ prl~r ~ U6e of ~r~
~t 1~ o~ Qtlo~
a roof drill b~ nd In~er~ ~herefor econQ~ a~ a~u~ ~nd ~o~ e~ e ~
l~is~lo~ed ~c¢ord~ng ~o ~h~ ln~en~ D ~ rong rota~ b~k, espeel~lly or o~e wl~ roof drlll~
15 b~ co~prlse~ a ~upFort~ng body haYing ~n ~ of rota-tlcn and R p~ir ~ ln~ert~. ~ach of t~e ~n~er~ a~
cuttin~ portlo~ ~c~n~ in ~he dl~ectlo~ of r~3t~tlo ms)un'c~D~ port~on an~ hen ~ ed iL~ ~ ~ir~ctlo~
parallel eo ~he a~s ~f ro~atlora, ~ cro~ ~ec~lo~l 20 on~îgur~tlon ~hi~ y~n~r~ ed~çe ~h~
The advantages or this two-prong bit over the prior art bit are many. One advantage of the two-prong bit is that it is s~ronger due to the wedge shape of the inserts~ Another advantage of the two-prong bit is the way it proceeds through the rockO
X5 The two-prong bit proceeds through the rock by first, fracturing and crushing the rock, then penetrating the 0~
~2~5~
fractured and crushed rockf and finally shearing the rock.
As a result of this cu~ting action, there is lower thrust and, consequently, lower wear of the inser~s.
Due to the lower wear of the inserts, there is also less friction generated during a drilling process so ~hat the drill can be operated at higher drilling speeds.
In contrast, the prior art drill bit as explained earlier crushes the ro~k, penetrates through the crushed rock and then shears the rock. Because it takes more energy to crush rock than to fracture it, this type of action requires higher thrust and higher wear on each of the inserts which will then generate more friction. As a consequence, the prior art drill bit has to be operated at a lower drillin~ speedO
Also disclo~ed as a separate article of commerce is an insert especially for use with a roof drill bit.
This insert comprises a generally wedge-shaped body.
I'here are two planar front faces tapering toward each other and intersecting so as to form a face cutting edge. Opposite to the face cutting edge the two planar front faces diverge and terminate in a mounting portion.
The insert also comprises a clearance face and a support face angularly related to and separated by the face cutting edge~ the clearance face intersecting the front faces so as to form two main cutting edges. The clear ance face also intersects the mounting portion.
Fi.nally, the face cutting edge and the two main cutting edges coincide in a common apexO
The apex of the wedge~shaped insert is an important feature of the invention since it has been proven to be effective in fracturing the rock, instead of crushing the rock as was the case with the prior art drill bit~
~RIEF ~ NGS:
The exact nature of the present invention will become more clearly apparent upcn reference to the following detailed specification taken in connection with the accompanying drawings in which:
Figure 1 is a perspective view of a prior art drill bit.
Figure 2 is a front view of the drill bit according to the invention.
Figure 3 is the drill bit of Figure 2 rotated 90 degrees.
Figure 4 is a plan view of the drill bit of Figur~s 2 and 3.
Figure 5 is an enlarged plan view of the inserts shown with the drill bit of Figures 2 to 4.
Figure 6 is a frontal view of another embodiment of a drill bit according to the invention.
Figure 7 is the drill bit of Figure 6 rotated 90 degrees.
Figure 8 is a plan view of the drill bit of Figures 6 and 7.
Figure 9 is an enlarged plan view of the inserts shown with the drill bit of Figures 6 to 8~
Figure 10 is an enlaryement of the plan view of the inse~t shown in Figure 9.
pETAILED _E CRIPTIO~ O~ T~E VENTION:
Referring to the drawings in more detail, and specifically referring to Figures 2 to 5, disc].osed according ~o the invention is a two-prong bit 12, especially for use with a roof drill ~not shown). ThP
bit comprises a supporting body 14 having an axis of rotation 16. There is a pair of inserts 18 r each of the inserts 18 having a cutting portion 20 facing in the direction of rotation 22, a mounting portion 24 and, when viewed in a direction parallel to the axis of rotation 16, a cross sectional configuration which is generally w~dge shaped.
In operation, one end lS of the supporting body would be attached to the roof drill. End 15 would typically have an hexagonal cross section, as is partially shown at 17 in Figure 4 for connection with a similar hexagonal configuration on the roof drill.
The cutting portion 20 of each of the inserts 18 comprises two planar front faces 26 extending ~orwardly in the rotational sense and axially so as to intersect each other and a clearance face 28. With reerence to Figure 4, the direction of rotation is shown at 22, and it can be seen that the cutting portion of each o~ the inserts faces and rotates in the direction of rotation.
~2~5~
The intersection of the planar front faces forms a face cutting edge 30 at the forwardmost part of the insert.
Further, ~he intersection of each of the planar front faces 26 with the clearance face 28 forms two main cutting edges 32. The face cutt.ing edge 30 and two ma.in cutting edges 32 coincide in a common apex 34~ The nature of the apex 34 is most clearly shown in Figures 2 and 3. Due to the pointed or nearly pointed nature of the apex, the rock is easily fractured.
The cutting portion 20 of each of the inserts 18 further comprises two lateral cutting edges 36, 38 formed by the intersection of the two planar front faces 26 and the mounting portion 24. One o the lateral cutting edges 36 or 38 is an inner lateral cutting edge 36 and the other lateral cutting edge i5 an outer lateral cutting edge 38.
As best seen in Figures 4 and 5, the mounting portion 24 is curvilinear when viewed parallel to the axis of rotation 16. In a pre~erred embodiment, the mounting portion is cylindrical as can also be seen in Figure 2.
Preferably, the dihedral angle 40, as best seen in Figure 5, between the two planar front faces, is 90 to 100 degrees. As best seen in Figure 3, it is preferable for each of the inserts that the clearance angle 42 is 15 to 20 degrees r the rake angle 43 is -10 to -20 degrees, and the included angle 44 between the face ~9--5~
cutting edge 30 and the clearance face 28 is 70 to 90 degrees~
It has been found that the strength of the i~sert is enhanced when the dihedral angle is 90 to 100 degrees and the included angle between the face cutting edge and the clearance face is 70 to 90 degrees. The insert will be the stronges~ when the dihedral angle 40 is 100 degrees and the included angle 44 is 90 degrees.
It has also been found ~hat thrust requirements are minimized when the clearance angle 42 is 15 to 20 degrees and the rake angle 43 is -10 to -20 degrees.
At each of the lateral cutting edges 36, 3~, the angle 46, as best seen in Figure 5, between the planar front face 26 and a plane 48 tangent to the mounting ]5 portion 24 is 90 degrees~ Constructing the insert so that the mounting portion intersects with the planar ~ront ~ace at an angle of 90 degrees is important for two reasons. The first is that the insert is made stronger and the second reason is that the lateral cutting edge is sharper.
The drill bit 12 has an outside diameter 50, as measured between the respective outer lateral cutting edges, and an inside diameter 52, as measured between the respective inner lateral cutting edges. This is best seen in Figures 2 and 4. It is preferred that the outside diameter is about five times greater than th~
inside diameter. When the ratio of the outside to inside diameter is held at about five, it is insured that the central portion of the hole not cut by the inserts is not so large as to prevent further movement o~ the drill bit in~o ~he hole. At the same time, if the ratio of the outside diame~er to the inside diameter is much greater than five, thrust re~uirements would be increased. Preferably, the ratio of the outside diameter to the inside diameter should be in the range of ~.7 ~o 5.2.
When the bit is viewed parallel to the axis o~
rotation 16, a first line 54 passing through the inner and outer lateral cutting edges of one of the inserts will be parallel with a second line 56 passing through the inner and outer lateral cutting edges of the other insert. Preferably, the first 54 and second 56 lines are forward in the rotational sense with respect to a diametric line 58 which is perpendicular to the rota-tional axis 16 of the bit~ By staggering the inserts with respect to the diametric line 58 as is done in the preferred embodiment, it is believed that thrust reyuirements will be reduced.
In one embodiment of the drill bit, the main 32 and ~ace cutting edges 30 are rectilinear.
The central portion 21 of the supporting body 14 is beefed up so as to strengthen the body. Additionally, the top of the central portion 21 has sloping faces 23 which slope away from the center of the body. Slopin~
faces 23 assist in the removal of the cut rock.
5~
In another embodiment of the drill bit, as shown in Figures 6 through 10, the two main cutting edges 32 are rectilinear and the face cutting edg~ 60 is cylindrical.
The cylindrical nature of the face cu~ting edge is best seen in ~igures 8 through 10.
It has been found that the wedge--shaped insert is suitable for drilling in soft rock as well as in very hard rocX; however, it has also been found that, when drilling in very hard rock, it is best that the ~ace cutting edge 60 have a cylindrical shape. The cylin-drical shape assists in, first, strengthening the insert and, second, preventing the insert from chipping.
In all other respects, the drill bit of Figures 6 through 10 is equivalent to the drill bit of Figures through 5O
Referring again to the drill bit of Figures 6 through 10, and specifically referring to Figure 10, the radius 62 of the cylindrical mounting portion 24 is R
and the radius 64 of the cylindrical cutting edge 60 is .5 to .707R when the dihedral angle 70 between the two front faces is 90 degrees. When the dihedral angle between the two planar front faces is 10~ degrees, then the radius 62 of the cylindrical mounting portion would be R and the radius 66 of the cylindrical cutting edge 70 would be .5 to .643R.
The radius R of the cylindrical mounting portion is measured from point 61 which is the intersection of the extensions of planar front faces 26. In our experience, the values of R will range from about .29 inches for a one inch diameter drill bit to about .43 inches for a one and one-half inch diameter drill bit.
Disclosed also as a separate article of commerce is S an insert 18 especially for use with a roof drill bit 12.
Referring specifically now to Figures 2 through 5, the insert has a generally wedge-shaped bodv. Two planar front faces 26 taper ~oward each other and inter-sect so as to form a face cutting edge 30. Opposite to the face cutting edge, the two planar front faces diverge and terminate in a mounting portion 24. There i.s also a clearance face 28 and a support face 68 angularly related to and separated by the face cutting edge 30. As seen best in Figure 3, the clearance face and support face form the top and bottom, respectively, of the insert. While the clearance ~ac~ and the support face may be parallel, it is not necessary to achieve the objects of the invention that they be parallel and~ in fact, as shown in Figure 3, they are not parallel. The clearance face 28 intersects the front faces 26 so as to form two main cutting edges 32. The clearance face 28 also intersects the mounting portion 24. The face cutting edge 30 and two main cutting edges 32 coincide in a common apex 34.
The insert further comprises two lateral cutting edges 36, 38 formed by the intersection of the two planar front faces 26 and the mounting portion 24.
The mounting portion, as best seen in Figures 4 and 5, is curvilinear when viewed from the clearance face.
It is preferred that the mounting portion be cylindrical as seen in Figure 2.
S Preferably, the dihedral angle 4n between the two planar front faces 26 is 90 to 100 degrees, and included angle 44 between ~he face cut~ing edge 30 and the cl~ar-ance face 28 is 70 to 90 degrees. For the ultimate in insert strength, it is most preferred that the dihedral angle 40 be 100 degrees and the included angle 44 be 90 degrees.
It is also preferable tha~ at each of the lateral cutting edges 36, 38, the angle 46 between the planar front face 26 and a plane 48 tangent to the mounting portion ~4 be 90 degrees.
In the emhodiment of the insert as shown in Figures 2 to 5, the main 32 and face 30 cutting edges are recti-linear.
Referring now to Fîgures 6 through 10, another ~0 embodiment of the insert according to the present inven-tion is shown. In all respects, the insert shown in Figures 6 to 10 is similar to the insert seen in Figures 2 to 5 except that the face cutting edge 60 is cylindri-cal instead of rectilinear.
It is preferred that when the dihedral angle 70 between the two planar front faces is 90 degrees and the radius 62 of the cylindrical mounting portion is R, then the radius 64 of the cylindrical cutting edge 60 is .5 to .707R. When ~he dihedral angle 72 between the two planar front faces is 100 degrees, then the radius 6~ of the cylindrical face cutting edge 60 is .5 to .643R.
This is best shown în Figure 10.
5 TEST: RESULTS:
Applicant has undertaken comparative performance testing between the prior art standard center vacuum bit as shown in Figure 1, and a wedge-shaped inserted bit according to this invention~ In Table 1, the bit geometry is described for each of the standard bit and the wedge-shaped inserted bit.
Each of the drill bits was drilled into a sample uf Barre granite, which is a hard ype of rock. The tes~s began by starting approximately at the same initial thrust. The operator of the drilling rig would then attempt to maintain a constant penetration rate for earh of the drill bits. When the penetration rate began to decrease, thrust would be increased. Penetration rate and thrust were constantly monitored. After the test hole of about 28 inches in length was completed, the thrust at completion ~maximum thrust) was noted. The drill bits were then removed from the drilling rig and examined for wear. Finally, specific wear ~width of wear land per feet of hole drilled~ for the drill bits was calculated.
Table 2 shows results of the testing.
Even though an attempt was made to maintain a constant penetration rate for both types of bits, the standard bit fell behind the wedge-shapecl inserted bit, notwithstanding th~ increased amount of t:hrust applied.
I~ should be noted that the maximum thrust of 7497 pounds applied to the s~andard bit is close to the critical thrust load at which point sufficient heat due to friction will be generated that the hardness of the cemented carbide will begin to decrease If this critical thrust load is maintained for any length of kime, the drill bit will self-destruct.
Most noteworthy of the test results is the compara-tive wear of the bits. The standard bit exhibited over one hundred percent more specific wear than the wedge-shaped inserted bit~
Several conclusions can be drawn from the results in Table 2. Overall, the wedge-shaped inser~ed bit performed much better than the standard bit. The wedge-shaped inserted bit can drill faster and at lower thrust levels a~d sufEers less wear than the standard bit~
Ultimately, by drilling at lower thrust levels, there is less chance that the insert will break, and by drilling with less wear, this means that the bit can be used for longer periods of time and so will be cost effective.
T~BLE 1 Insert ShapeStandard Wçdged Bit Geometry Rake Angle 0 -10 Clearance Angle 20 15 Included Angle 70 85 Dihedral Angle - 98 ~T~B4E
Insert ShapeS~andar~
Initial Thrust, lbs. 1536 1700 Average Thrust, lbs. 56S5 4409 Maximum Thrust, lbs. 7497 6116 Penetration Rate, In./Min. 10.7 12.6 Specific Wear, In./Ft. .079 .036 Modifications may ~e made within the scope of the appended claims.
Claims (18)
1. A two-prong bit especially for use with roof drills comprising: a supporting body having an axis of rotation;
a pair of inserts, each of said inserts having a cutting portion facing in the direction of rotation, a mounting portion and, when viewed in a direction parallel to the axis of rotation, a cross sectional configuration which is generally wedge-shaped and forms a longitudinally extending face cutting edge at the apex of said wedge.
a pair of inserts, each of said inserts having a cutting portion facing in the direction of rotation, a mounting portion and, when viewed in a direction parallel to the axis of rotation, a cross sectional configuration which is generally wedge-shaped and forms a longitudinally extending face cutting edge at the apex of said wedge.
2. The bit of claim 1 wherein the cutting portion of each of said inserts comprises two planar front faces extending forwardly in the rotational sense and axially so as to intersect each other and a clearance face, the inter-section of the planar front faces forming said face cutting edge at the forward most part of the insert and the inter-section of each of the planar front faces with the clearance face forming two main cutting edges, the face cutting edge and two main cutting edges coinciding in a common apex.
3. The bit of claim 2 wherein the cutting portion of each of the inserts further comprises two lateral cutting edges formed by the intersection of the two planar front faces and the mounting portion, one of said lateral cutting edges being an inner lateral cutting edge and the other being an outer lateral cutting edge.
4. The bit of claim 3 wherein said mounting portion is curvilinear when viewed parallel to the axis of rotation.
5. The bit of claim 4 wherein the dihedral angle between the two planar front faces is 90 to 100 degrees.
6. The bit of claim 4 wherein the clearance angle for each of said inserts is 15 to 20 degrees.
7. The bit of claim 4 wherein the rake angle for each of said inserts is -10 to -20 degrees.
8. The bit of claim 4 wherein the included angle between the face cutting edge and the clearance face is 70 to 90 degrees.
9, The bit of claim 4 wherein at each of the lateral cutting edges, the angle between the planar front face and a plane tangent to the mounting portion is 90 degrees,
10. The bit of claim 4 having an outside diameter, as measured between the respective outer lateral cutting edges, and an inside diameter, as measured between the respective inner lateral cutting edges, wherein the outside diameter is about five times greater than the inside diameter.
11. The bit of claim 10 wherein the outside diameter is 4.7 to 5.2 times greater than the inside diameter of the bit.
12. The bit of claim 4 wherein said mounting portion is cylindrical.
13. The bit of claim 12 wherein when said bit is viewed parallel to the axis of rotation, a first line passing through the inner and outer lateral cutting edges of one of the inserts will be parallel with a second line passing through the inner and outer lateral cutting edges of the other insert.
14. The bit of claim 13 wherein said first and second lines are forward t in the rotational sense, with respect to a diametric line which is perpendicular to the rotational axis of the bit.
15, The bit of claim 14 wherein the main and face cutting edges are rectilinear.
16. The bit of claim 14 wherein the two main cutting edges are rectilinear and the face cutting edge is cylindrical.
17. The bit of claim 16 wherein the radius of said cylindrical mounting portion is R and the radius of said cylindrical cutting edge is 0.5 to 0.707R when the dihedral angle between the two planar front faces is 90 degrees.
18, The bit of claim 16 wherein the radius of said cylindrical mounting portion is R and the radius of said cylindrical cutting edge is 0.5 to 0.643R when the dihedral angle between the two planar front faces is 100 degrees.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US53876583A | 1983-10-03 | 1983-10-03 | |
| US538,765 | 1983-10-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1220059A true CA1220059A (en) | 1987-04-07 |
Family
ID=24148333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000461321A Expired CA1220059A (en) | 1983-10-03 | 1984-08-20 | Two-prong rotary bit, especially for use with roof drills, and insert therefor |
Country Status (5)
| Country | Link |
|---|---|
| AU (1) | AU571262B2 (en) |
| CA (1) | CA1220059A (en) |
| DE (1) | DE3436128C2 (en) |
| GB (1) | GB2149329B (en) |
| ZA (1) | ZA846838B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5180022A (en) * | 1991-05-23 | 1993-01-19 | Brady William J | Rotary mining tools |
| DE4134425A1 (en) * | 1991-10-18 | 1993-04-22 | Boart Hwf Gmbh Co Kg | Rotary drilling head with cutter supports - has hard metal cutters welded to twin holders and supported at back and underneath |
| AU717071B1 (en) * | 1999-10-29 | 2000-03-16 | Sandvik Intellectual Property Ab | Self drilling roof bolt |
| US6637521B2 (en) * | 2001-07-11 | 2003-10-28 | Hilti Aktiengesellschaft | Earth borer |
| DE102006000085B3 (en) * | 2006-02-21 | 2007-10-11 | Hilti Ag | wellhead |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1050116A (en) * | ||||
| US1858988A (en) * | 1928-04-23 | 1932-05-17 | Reed Roller Bit Co | Drill bit |
| DE612147C (en) * | 1930-08-29 | 1935-04-13 | Gewerkschaft Wallram | Rock drill |
| GB669636A (en) * | 1947-07-04 | 1952-04-09 | Louis Camille Andre Gardelle | Improvements in or relating to rock drills |
| GB685967A (en) * | 1950-12-02 | 1953-01-14 | Jessop William & Sons Ltd | Improvements in or relating to rotary bits for coal and like drilling |
| GB705020A (en) * | 1952-04-28 | 1954-03-03 | Cons Pneumatic Tool Company Lt | Improvements relating to rotary bits for wet drilling coal and other hard substances |
| GB736982A (en) * | 1952-10-25 | 1955-09-14 | Howard & Dennis Ltd | Improvements in cutters for mowing and like machines |
| GB822029A (en) * | 1956-03-15 | 1959-10-21 | Coal Industry Patents Ltd | Improvements in or relating to scroll-type drilling tools |
| AT223151B (en) * | 1960-08-16 | 1962-09-10 | Hard Metals Ltd | Rotary cutting tool |
| FR2194512B3 (en) * | 1972-07-27 | 1976-07-09 | Tarmac Engineering Ltd | |
| DE2718920A1 (en) * | 1977-04-28 | 1978-11-09 | Wallram Hartmetall Gmbh | Stone cutting head with three radial cutting inserts - has hard metal plate shaped inserts with convex cutting faces |
| ZA782286B (en) * | 1978-04-21 | 1979-10-31 | Christensen Inc | Abrasive bodies |
| FR2479825A1 (en) * | 1980-04-04 | 1981-10-09 | Fabre Sa Pierre | BENZODIOXAN 1,4 METHOXY-2 PROPANOLAMINES, THEIR PREPARATION AND THEIR USE AS MEDICAMENTS |
| DE8107329U1 (en) * | 1980-05-08 | 1981-08-13 | Marwin Cutting Tools Ltd., Rothley, Leicestershire | "MACHINE CUTTING TOOL" |
-
1984
- 1984-08-20 CA CA000461321A patent/CA1220059A/en not_active Expired
- 1984-08-23 GB GB08421443A patent/GB2149329B/en not_active Expired
- 1984-08-31 ZA ZA846838A patent/ZA846838B/en unknown
- 1984-09-05 AU AU32736/84A patent/AU571262B2/en not_active Ceased
- 1984-10-02 DE DE3436128A patent/DE3436128C2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2149329A (en) | 1985-06-12 |
| DE3436128C2 (en) | 1986-08-14 |
| ZA846838B (en) | 1985-04-24 |
| GB2149329B (en) | 1987-10-21 |
| DE3436128A1 (en) | 1985-04-25 |
| GB8421443D0 (en) | 1984-09-26 |
| AU3273684A (en) | 1985-04-18 |
| AU571262B2 (en) | 1988-04-14 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |