US985168A - Device for cutting screw-threads. - Google Patents

Description

L. P. HART.. DEVICE FOR GUTTING scum THREADS. APPLICATION FILED APR. 20, 1907.

Patented Feb. 28, 1911.

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L. P. HART; DEVICE FOR CUTTING SCREW THREADS. APPLICATION FILED APR. 20, 1907.

985, 168.- Patented Feb. 28, 1911.

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UNI E STTS PATENT OFFICE.

LOUIS F. HART, OF CLEVELAND, OHIO, ASSIGNOR TO THE HART MANUFACTURING COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO,

DEVICE FOR. CUTTING SCREW-THREADS.

b all whom it may concern:

Be it known that I, LOUIS F. I-IA-RT, a citizen of the United States, resident of Cleveland, county of Cuyahoga, and State of Ohio, have invented a new and useful Improvement in Devices for Cutting Screw- Threads, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

My invention relates to devices for cutting screw threads, particularly for cutting screw threads on pipes and the like where it is generally desirable to make such thread with a taper in order to insure a tight fitting joint.

My invention accordingly has as its object the provision among other things of means for automatically producing such a tapered thread.

Other and equally important objects are the provision of means for quickly adjusting the device to fit work of different di mensions and to automatically positively release such work when the standard length of thread has been cut.

To the accomplishment of the above and related ends, said invention consists of means hereinafter fully described and particularly set forth in the claims.

The annexed drawing. and the following description set forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

Tn said annexed drawings: Figure 1 represents, in central longitudinal cross sec tion, a die stock embodying the several improved features of construction of my invention; Fig. 2 is a front elevation of such device: Figs. 3, 4t anc 5 are respectivelya front elevation, a plan and an end elevation of an adjustable catch forming a feature of such invention; Fig. 6 is a cross sectional detail corresponding to that appearing in Fig. 1, but showing the parts in a different operative position; Figs. 7 and 8 are respeetively a bottom plan view and a transverse cross section of a grooved rider-bar that Specification of Letters Patent.

Application filed. April 20, 1907.

Patented Feb. 28, 1911.

Serial No. 369,246.

forms another feature of said invention; and Fig. 9 is an end view of a plunger forming a part of the catch shown in Figs. 3, f and 5.

As has been stated the specific form of device chosen as best illustrating my invention is a pipe-threading tool or die stock. The general form of such tool or machine as it may be variously designated, depending upon the size of work it is designed to accommodate, and upon whether it is to be operated manually or by power, is clearly shown in Figs. 1 and 2. From an inspection of these figures the tool will be seen to be made up of two main elements, a stock holding frame member A, and a die-holding member or head revolubly mounted in said frame member. Frame member A, althoughintegral in actual construction, may

be regarded as being made up of three concent ic but aXia-lly separated annular portions at, a and a joined together by connecting portions a. Annular portion a of the frame is designed to serve as the work holding device. To this end it is provided with a. removable guide sleeve A of the usual construction. In the type of tool illustrated it is of course intended that the pipe should be held against rotation in a suitable vise or the like, the purpose of the work holding mechanism just described being merely to hold the tool frame from rotation on the pipe. However, by providing frame A with a foot or base whereby it can be attached to work bench or the floor, use of such a vise may be obviated.

Annular portion a. of the frame A is of larger diameter than portion (6 and the inner faces of both portions form bearings for the die holding member or head B. Said die-holding member or head comprises a sleeve portion B thus journaled within parto of the frame, and a flange portion B journaled in part a Such bearing is formed directly by the face of the annular portion (i in the case of portion o however, a bushing A Fig. 1, is introduced. This bushing is designed to be removably secured in place and is provided with an integral collar a adapted to fit against frame portion a Such bushing is designed to operate as a leader ring, its rear end being formed to present a cam surface a as shown in Fig. 1, this surface being of a suitable pitch to start or lead the dies onto the work. Disposed toco-operate with such cam surface a is a roller Bt mounted on the rear end of sleeve portion B of the die-holding member B. By cooperation of such roller'and cam face thedie holdingmember is obviously moved forward during its first turna distance equal to the pitch ofthe cam and thereby j the work; the feeding for the-remaining turns, is intended to'be left entirely to the dies, a form'ofdiefespecially designed to thus tit-itself on the work being fully described and claimed "in my copending application filed ll [arch 23, 1906, Serial "No. 307,598. p a 3 7 p s 4 On one side of fram e'A preferably inter- -mediately of two connecting portions are provided bearings a in which is V journaled V a short shaft A held in place'thereinby' a collar a secured to its one end, and shaped thereof. By this means it will loeseen that rotary motion may be communicated to said between 1 face a collar attthat registers in such groove.

' square at the other end to receive a ratchet .25

tated. Splined on such shaft wrench, not shown, whereby it may be ro- A interme- 'diately of'its bearings'is a small pinion A V "that'is adapted to mesh with a gear-B secured on sleeve portion B 'of memben B and just to the rear of flange portion member B. An encircling notch b is formed the rim of flange B and tlnsgear B and pmion A has attached to he outer Thus the pinion is moved alongshaft- A as the gear is shifted longitudinally-with memand slidably hold the ber B within frame A, and-the two are kept constantly in mesh.

In'its flanged face, member B is provided with a plurality of radial slots or recesses b, Figs l and 2 that are designed to receive dies (1' The number of such slots and-corresponding dies may of course be varied as desired, therebeing four inthe form of device illustrated. The dies are normally retained in their respective slots by means of anannular plate D revolubly secured to the face of member B by l f means of a shoulder ring E, the latter being attached to-=suchmember by suitable screws Y in v iew of theconformation suchrotatlonlsadapted to permit their re- "lease" from such slots entirely. Manual roof cam grooves cl, Fig. 2,

e. 'Plate D bears on its inner'face a series where, however,

only one is shown in order to avoid confusion. Such grooves correspond in number and dlsposltion wlth 'dles C which are .formed with lntegral projections'or pins 0, Fig. 1, adapted to register inthe grooves. Rotation of the cam plate obviously serves to either advance or retract the dies in the slots as may be desired, and in one position, of the latter,

cause the dies to initially grip near such end so as to 'in the periphery of the latter it the rotatiy e movement required in adjusting theposition of the dies.

the bar.

in turn to secure a second to prevent further rotation 1n one. d1rect1on. The

tudinal movement relatively to said frame.

The outer end of the bar, in the normal position of the parts shown in Fig. 1, PIOJGCl'S a trifle beyond the front face of D,'and an elongated recess 0?,- Fig. 2, is cut so as to allow In the under side ofrider-bar B is provided a groove 1) of substantially helical form having the axis of the device as its axis and a pitch depending on conditions presently to be set forth. Such groove b Fig. 7, beginning near the forward'end of the bar extends for substantially half the length of the same and terminates in an inclined groove portion 6 that intersects one of the lateral edges of Said 7 bar is also formed on its under side with a transverse slot b that intersects the forward end of the groove 7), the bottom of said slot being outwardly beveled on one side of said groove and both inwardly and outwardly beveled on the other, see Figs. 7 and 8.

Cam plate D is provided on its face with a recess or T slot 03? of circular conformation adapted to receive bolts d which serve plate D Figs. 2, 3, 4t and 5, in any desired axial position on the cam plate. Such plate D bears on its upper edge a fixed stop member or stud d adapted to laterally engage rider bar B of the cam plate position of this stop member is designed to be such as to prevent rotation of the cam-plate D such as would be sufficient to entire'lyrelease the dies from cam-grooves 0! without first loosening bolts d andretracting plate D to the farther end of slot d In a radially disposed bore 03 in theforward end of said plate is mounted a catch or projection consisting of a plunger d that is normally upwardly actuated by a. spring, d

of the parts shown in Fig. 1 its upper end is adapted to enter the groove 6 in the rider bar B by way'of the transverse slot 7) intersecting the same, from either side of said bar. Once engaging such groove such engagement is continued as will be obvious by cam plate The disposition of this catch is such that in the normal assembled position there presented in its broader the pressure of the spring upwardly upon the plunger. To permit the catch to be manually withdrawn at any point in the course of its movement along this groove, its lower end is desirably provided with a milled head (5 So long as it remains positioned in the forward end of the groove, moreover, it is adapted to escape therefrom by virtue of the doubly beveled bottom of transverse slot 6 merely upon rotation of the cam-plate, its own end, Figs. 3 and 4:, being oppositely beveled to conform with the two difierent bevels of such slot bottom. The end of the plunger is furthermore flattened on two sides as shown in the end view thereof appearing in Fig. 9. The one ai of such flattened surfaces is designed to conform with that wall of helical groove b against which the plunger end is forced by the outward pressure of the dies when the device is in operation; the other flattened surface (Z is similarly shaped to conform with that wall of the inclined groove portion If against which the plunger end is pressed at the conclusion of the cutting operation. The walls of the respective groove portions, against which the plunger end thus presses in the case of the form of my device here illustrated, are indicated by small arrows in Fig. 7 In order that the catch may always properly present these flattened faces to the groove walls in question it is necessary that it be held against rotation in catch-plate D plunger is also and a small pin and contacts with such flat surface, 5 and 9.

The general combination of a rider bar with a stop plate adjustably mounted on the die'positioning cam plate is, it should here be explained, also shown and described in the earlier filed co-pending application here- .inbefore referred to, such combination being patent aspect.

Having thus described, with what is thought sufficient detail,- the structure of my improved threading tool, it only remains to indicate briefly its manner of operation. Assuming that a thread of a given pitch is to be cut on a section of pipe, the pipe in question will be first securely gripped in a vice. To adjust the thread cutting tool, dies of the pitch desired are fitted in slots 2) and the leader bushing A of pitch to correspond with such dies is fitted in annular portion a? of the frame. Aguide sleeve A of the proper diameter is next fitted in the frame of the tool and die-holding member 13 thereupon rotated to position roller B at the beginning of the cam or leader bushing A Then cam-plate D is rotated to bring the dies into proper position for cutting thread on the size of pipe in hand. In on der to facilitate this adjustment the faces flattened slightly on one side (Z intersects the bore cl Figs. 4,

To this end the body of the.

of the cam-plate and ring E are preferably provided with graduations as will be readily uiulerstood, by the alinement or registration of which the proper position is indicated. Thereupon catch-bearing plate D is moved along slot d until plunger (Z registers in the groove 71 in rider-bar B; bolts d are then drawn tight. The tool being now secured in place on the pipe with the pipe end resting on the inner beveled edge of the dies, the actual operation of cutting is begun by rotating shaft A and. thereby die-holding member B. The leader bushing A assists the dies in firmly gripping the stock during the first rotation of such member; upon further rotation of the latter the dies are designed to automatically advance on the stock as has been stated. 00- incidentally with the advance of the dies, and therefore of die-holding member B, upon the stock, a limited rotative movement of cam-plate D occurs by virtue of the construction of rider-bar B and plunger cl engaging therewith, by means of which movement the dies gradually retreat and so cut a tapered thread. The pitch of the groove (Z wherewith said plunger (Z engages, determines the amount of rotation imparted to the cam plate, and thus in conjunction with the degree of divergence of the cam grooves in taper of such thread, as will be obvious. This rotative movement of the cam plate relatively to the die-holding member or diehead during the cutting operation, may be imparted thereto either by the pressure of one wall of the groove portion 6 in the rider-bars under face against the plunger (F, or by the pressure or the dies in cam grooves (Z of the plate, in which case the other wall of such groove portion 5 serves to control the rotation of the plate. In either event a positive, yet at the same time a controlled or regulated, movement of the dies is obtained outwardly from the axis of the device. Thus if the cam-grooves (Z are sufficiently inclined, when the device is in operation, the pressure of the pipe against the dies will cause the cam-plate and the second plate D that carries plunger (Z to turn axially. lnder such conditions the turning of the cam-plate is controlled or limited by the plunger engaging with the lower side of the groove portion 7) in the bottom plan view of rider-bar B designated by the arrow in Fig. 7. On the other hand, if the inclination of the cam grooves (Z is such as to render that component of the outward thrust-of the dies, which tends to rotate the cam-plate, insutlicient to overcome the frictional and other resistance, the turning of the plate will be brought about by the other side of groove engaging with the plunger d". Otherwise stated, when the cam-plate is formed with grooves of the latter determines the relatively littleinclination,

retraction, of the dies is caused by the action of groove Z2 turning of the plate; whereas, when the slots iuthe rider barefiecting the are of greater inclination, such that the pressure of th'e'dies imparts a' rotative tend- .ency thereto, theretraction of the latter is been cut the'plunger (Z enters permitted and uniformly controlled in a same to cease cutting." The final turn forsuch asmight permit ward given memberB, incidentally to this retraction of the dies,'serves automaticallv to clean out the thread-and remove the bur from them; no additional movement or operation, inother words, is necessary to accomolish this im )ortant result. T withdraw the tool, the cam plate D is then simply-rotated through :the medium of handle D" suflicientlyto entirely free the dies from the stock, and, upon releasing the stockholding device, the tool can be forthwith I removed. Undue rotation of the cam-plate, the dies to escape from' thecam-plate and fall out, is. prevented by engagement of thecrider-bar B with stop d, as has been previously explained. I 7 When the cam-grooves d are properly, designed so as to function in one or the .otherof the two ways above described, it'is I obvious that but one wall of the groove portion 6 will operate in the manner v the predetermined, or full, length of thread '55,

'of'the'cut, such portion 6 is really required, since the plunger will remain in contact therewith throughout the whole of its normal travel along the .rider bar. It will be-equally evi-- dent that the more sharply inclined groove explained, irrespective of which wall the plunger has thus. followed. 7 In otherwords it is contemplated that, even where the outward pressure of v the dies is utilized ,to impart a rotative tendency to the cam-plate, such tendency may not in all cases produce the quick-opening. eifect desired. This inclined :groove-portion, when has been out. 'As a matter of. fact, such positive opening means may be dispensed with in the caseof the cam-plate actuated by the pressure of the dies, and this pressure reliedon aloneto relieve said dies at the end being the construction which I describe in my co-pending application,

Serial No; 307,598, to which I have herein- =beforec referred.

tion on the. same size of the recession, or

andis thereby forced out of enholding member.

stock, all that is for purposes of adjustment or otherwise,

this is permitted by the double bevel of the other portion of such transverse slot.

The manner in which. my tool may be adjusted to cutting thread on a different size of stock f should be sufiiciently obvious to those skilled in the art from what has been said abovev of its construction and mode of operation. That to which I particularly desire to call attention is the means whereby a tapered thread is produced automatically pending the cutting operation.

Such means aside from being quite simple and in themselves easy of adjustment, are as has been explained, positive in action, and assure not merely the cutting of a thread of exactly the right taper but also therelease of the dies from the stock at the close of such cutting operation. At the same time thevarious other adjustments embodied in the type of thread cutting tool herein described are in no wise interfered with' by the inclusion of such taper threading means. It should be stated in conclusion that I contemplate, as coming within the scope of my invention, a reversal orexchange of position as regards the riderbar and catch engaging therewith. In other'words the groove of the rider-bar might be provided in connection with the cam-plate andthe plunger with the die- One specific construction embodying this arrangement of the parts in question will be found illustrated and described in another co-pending application filed April28, 1909, Serial No. 492,622.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any one of the following claims or. the equivalent of such stated. means be employed.

i I therefore particularly point out and distinctly claim as my invention 1. In a screw-cutting device, the combinationof work-holding means and a member longitudinally and rotatably movable with referenceto each other; dies movable in said member; an element carried by said mem her and operatively connected with said dies to position the same; and another element rotatable but not longitudinally movable with said member, said elements being adapted; to inter-engage upon a predetermined longitudinal movement between said work-holding means and member to positively withdraw said dies from the work.

2. In a screw-cutting device, the com bination of work-holding means and amember longitudinally and rotatably movable with reference to each other; dies movable in said member; means adapted to control movement of said dies outwardly upon relative longitudinal movement between said work-holding means and member; and means adapted positively to withdraw said dies from the work upon a predetermined amount of such movement.

8. In a screw-cutting device, the combination of work-holding means and a member longitudinally and rotatably movable with reference to each other; dies movable in said member; means adapted to control movement of said dies outwardly upon relative longitudinal movement between said work-holding means and member; and elements adapted to inter-engage upon a predetermined amount of such movement to positively withdraw said dies from the work;

4. In a screw-cutting device, the combination of work-holding means; a member longitudinally and rotatably movable with reference thereto; dies movable in said member; means adapted automatically to retract said dies as said member moves longitudinally; and means adapted positively to withdraw said dies from the work upon a predetermined amount of such movement.

5. In a screw-cutting device, the combination of work-holding means, a member longitudinally and rotatably movable with reference thereto; dies movable in said members; means adapted automatically to retract said dies as said member moves longitudinally; and elements adapted to inter-engage upon a predetermined amount of such movement to positively withdraw said dies from the work.

(3. In a screw-cutting device, the combina tion of a frame; a member longitudinally and rotatably movable therein; dies movable in said member; a bar longitudinally movable with respect to said member and held against such movement relatively to said frame; and a cam-plate rotatably secured to said member and adapted to position said dies, said bar and cam-plate being provided with elements adapted to inter-engage upon a predetermined amount of longitudinal movement on the part of said bar to positively withdraw said dies from the work.

7 In a screw-cutting device, the combination of a frame; a member longitudinally and rotatably movable therein; dies movable in said member; a bar longitudinally movable with respect to said member and held against such movement relatively to said frame; and a cam-plate rotatably secured to said member and adapted to position said dies, said bar and cam-plate being provided the one with a groove and the other with a projection adapted to engage such groove, the latter being formed to positively with draw said dies from the work upon a predetermined amount of longitudinal movement on the part of said bar.

8. In a screw-cutting device, the combination of a frame; a member longitudinally and rotatably movable therein; dies movable in said member; a bar longitudinally movable with respect to said member and held against such movement relatively to said frame; and acam-plat'e rotatably secured to said member and adapted to position said dies, said bar being provided with a groove and said cam-plate with a projecting element adapted to engage such groove, the latter being formed to positively withdraw said dies from the work upon a predetermined amount of longitudinal movement on the part of said bar.

9. In a screw-cutting device, the combination of work-holding means and a member longitudinally and rotatably movable with respect to each other; dies movable in said member; a bar longitudinally movable with respect to said member and held against such movement relatively to said workholding means; and a plate movably secured to said member and adapted to posi-, tion said dies, said bar being adapted to engage said plate to positively move the same relatively to said member pending a predetermined longitudinal movement of the latter, the length of the engaging faces of said bar and plate being proportioned to the length of thread to be cut, whereby said plate is left free to move upon proper longitudinal movement of said bar with respect to said member.

10. In a screw-cutting device, the combination of work-holding means and a member longitudinally and rotatably movable with respect to each other; dies movable in said member; a bar longitudinally movable with respect to said member and held against such movement relatively to said work-holding means; and a plate movably secured to said member and adapted to position said dies, said bar being adapted to engage said plate to positively move the same relatively to said member pending a predetermined longitudinal movement of the latter, the respective engaging faces of said bar and plate being formed to effect such movement at varying rates of speed, and the length of the portion of said faces for effecting the normal rate of speed being proportioned to the length of thread to be cut, the other rate of speed serving to move said plate to free the dies from engagement with the work.

' oured to said member V 11; Ina screw-cutting device, the combination of a frame; a member longitudinally androtatably movable therein; dies movable in said member; 'a'bar longitudinally "movable with respect to saidmember, and relatively to held against such movement said frame;'and a cam-plate rotatably se and adapted to pos1- tion said dies, said bar being adapted to en- ;gage. said cam-plate to positively rotate the same relatively to said member pending a predetermined longitudinal movement of the latter, the length of the engaging faces of said bar and cam-plate being proportioned to the length of thread to be cut, whereby said cam-plate is left free torotate' upon proper longitudinal movement of said bar with respect to said member;

12. In ascrew-cutting device, the combination of a frame; a member longitud nally and rotatably movable therein; dies movable insaid member, a barlongitudinally movable'with respect to said member and held against such movement relatively to. said frame, and a cam-plate rotatablv secured to said member and adapted to position said dies, said bar being'adapted to engage said oam plate and to positively rotate the same relatively to said member, pending a predetermined longitudinal movement of the latgter, the respective engaging faces of said bar andram-plate being formed to effect {such rotation at varying rates ofspeed, and

- ,t'helength ofthe portion of said facesfor i effecting the normal rate of speed being proportioned to the length of thread tobe cut,

" theother. ing'to rotate said cam-plate to rate of speed, thereupon had, serv,- free the dies from engagement with the work.

13. In a screw-cutting device, the combignation of. work-holding means, a" member longitudinally and rotatably movable with movable with respect to said member and held against such movement relatively to said frame; and a cam-plate rotatably se- I cured to said member and adapted to posithe work, and 'the element on tion said dies, said bar and cam-plate being provided with elements adapted to interengage' upon a predetermined amount of longitudinal movement on the part of said bar to positively withdraw said dies from said cam-plate being adjnstably positioned thereon.

15. In a screw-cutting device, thecombiin said member, a bar nation of a frame, a member longitudinally and rotatably movable therein, dies movable longitudinally movable with respect'to said member and held against longitudinal movement relatively to said frame, said bar being formed with a guide-way on its inner face, a cam plate rotatably secured to said member and adapted to position said dies, and a radially disposed spring pressed catch borne by said cam-plate and adapted to engage said guide-way.

16. In a screw-cutting device, the combination of a frame, a member longitudinally and rotatably movable therein, dies movable in said member, a bar longitudinally movable in said member and held against longitudinal movement relatively to said frame, said bar being provided, on its inner face with a groove inclined with 'espect to a line parallel with the axis of the device and intersecting a lateral edge of said bar, a camplate rotatably secured to said member and adapted to position said dies, and a radially disposed, spring-pressed, catch borne by said cam-plate and adapted to engage the groove in said bar.

17. In a screw-cutting device, the combination of a frame, a member longitudinally and rotatably movable therein, dies movable in said member, a bar longitudinally movable with respect to, said member and held against longitudinal movement relatively to said frame, said bar being provi ded 011 its inner face with a helical groove having the axis of the device as its axis, a cam-plate rotatably secured to said-member and adapted to position said dies, a radially. disposed catch born by said cam-plate, and a spring normally pressing said catch outwardly to engage the groove in said bar.

18. In a screw-cutting device, the combination of a frame comprising alined annular portions; a flanged sleeve longitudinally and rotatably mounted in said bar longitudinally movable in the periphery of such flange and held" against longitudinal movement with respect to said frame, said 'bar being provided on its inner face with a groove comprising a portion of helical form with the axis of the device as its axis and an inclined portion continuous therewith and intersecting a lateral edge of said bar; a

cam-plate rotatably secured on the face of said flangeand engaging said dies to position the same; a radially disposed catch ad.- justably mounted on said cam-plate; and a spring normally pressing said catch outwardly to engage the groove in said bar.

19. In a screw-cutting device, the combination of a frame, a member longitudinally and'rotatably movable therein, dies movable in said member, a bar longitudinally movable in said member and held against longitudinal movement relatively to said frame,

)ortions; dies movable 1n the flange of said -s eeve; a ridersaid bar being provided on its inner face with a groove inclined with respect to a line parallel with the axis of the device and with a transverse slotintersecting the forward end of said groove, a cam-plate rotatably secured to said member and adapted to position said dies, and a radially disposed plunger borne by said cam-plate and adapted to enter the groove in said bar by way of such transverse slot.

20. In a screw-cutting device, the combi nation of a frame, a member longitudinally and rotatably movable therein, dies movable in said member, a bar longitudinally movable in said member and held against longitudinal movement relatively to said frame, said bar being provided on its inner face with a groove inclined with respect toa line parallel with the axis of the device and with a transverse slot intersecting the forward end of said groove, the bottom of said slot being outwardly beveled on one side of said groove and both inwardly and outwardly beveled on the other, a cam-plate rotatably secured to said member and adapted to position said dies, and a radially disposed plunger borne by said cam-plate and adapted to enter the groove in said bar by way of such transverse slot.

21. In a screw-cutting device, the combination of a frame comprising alined annular portions; a flanged sleeve longitudinally and rotatably movable in said portions; dies movable in the flange of said sleeve; a rider-bar longitudinally movable in the periphery of such flange and held against longitudinal movement wlt-h respect to said frame, said bar being provided on its inner face with a groove comprising a portion of helical form with the axis of the device as its axis and an inclined portion continuous therewith and intersecting a lateral edge of said bar, and with a transverse slot intersecting the forward end of said groove, the bottom of said slot being outwardly beveled on one side of said groove and both inwardly and outwardly beveled on the other; a cam-plate rotatably secured on the face of said flange and engaging said dies to posi tion the same; a radially disposed plunger adjustably mounted on said cam-plate and adapted to enter the groove in said bar by way of such transverse slot; and a spring adapted to retain said plunger in engagement with such groove.

22. In a screw-cutting device, the combination of a frame comprising alined annular portions; a flanged sleeve longitudinally and rotatably mounted in said portions; dies movable in the flange of said sleeve; a rider-bar longitudinally movable in the periphery of such flange and held against longitudinal movement with respect to said frame, said bar being provided on its inner face with a groove comprising a portionof helical form with the axis of the device as its axis and an inclined portion continuous therewith and intersecting a lateral edge of said bar, and with a transverse slot intersecting the forward end of said groove, the bottom of said slot being outwardly beveled on one side of said groove and both inwardly and outwardly beveled on the other; a camplate rotatably secured on the face of said flange and engaging said dies to position the same, a radially disposed plunger adjustably mounted on said cam-plate and adapted to enter the groove in said bar by way of such transverse slot, said plunger having its outer end oppositely beveled to conform with the oppositely beveled bottom of such slot; and a spring adapted to retain said plunger in engagement with such groove.

23. In a screw-cutting device, the combination of a frame, a member longitudinally and rotat-ably movable therein, dies movable in said member, a bar longitudinally movable with respect to said member and held against longitudinal movement relatively to said frame, said bar being provided on its inner face with a helical groove having the axis of the device as its axis, a cam-plate rotatably secured to said member and adapted to position said dies, and a radially disposed plunger borne by said cam-plate and adapt ed to engage the groove in said bar, said plunger being held against rotation and having its end flattened to conform with walls of said groove.

24:. In a screw-cutting device, the combination of a frame, a member longitudinally and rotatably movable therein, dies movable in said member, a bar longitudinally movable in said member and held against longitudinal movement relatively to said frame, said bar being provided on its inner face with a helical groove having the axis of the device as its axis, a cam-plate rotatably secured to said member and adapted to position said dies; and a radially disposed plunger borne by said cam-plate and adapted to engage the groove in said bar, said plunger having its engaging end flattened on one side to conform with the side of said groove against which the pressure of the dies forces said plunger when said dies are in operation.

25. In a screw-cutting device, the combination of a frame, a member longitudinally and rotatably movable therein, dies movable in said member, a bar longitudinally movable in said member and held against longitudinal movement relatively to said frame, said bar being provided on its inner face with a groove comprising a portion of helical form with. the axis of the device as its axis and an inclined portion continuous therewith and intersecting a lateral edge of said bar; a cam-plate rotatably secured to said member and adapted to position said dies; and a radially disposed, springpressed, plunger bornefby said cam-plate groove portion against which it presses at vand adapted to engage the groove in said the conclusion of such operation.

flattened 0n onesi'de to vcqnfci 'm With the bar, said plungen'having its engaging end I 5 wall of said helical, groove portion against v L HARI' f which itpressed' duiingthe cutting oper- Attested by aticn of the dies and another side flattened D. T. DAvnzs,

to conform with the Wall "of said inclined JNo. F. OBERLIN.

Copies of this patent may be cbtained for five cents each, by addressing the Commissioner of Patents,

- Washington, D. C.

10 Signed by me, this 18th day of April 1907.

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