US2204866A - Threading tool - Google Patents

Description

THREADING TOOL Filed Jan. 4. 1939 ATTORNEYS.

Patented June 18, 1940 UNITED STATES PATENT ,OFF'I'CE 8 Claims.

This invention relates to threading tools and more particularly to threading tools of the chaser type by which the thread is completely cutby one pass of the tool.

Considerable difliculty is experienced in cutting a smooth and uniform thread in metals due to the fact that the thread is in the nature of a groove, the bottom of which, in the case of the V I threads and Acme threads, is comparatively mar- 10 row, and the sides of the thread extend in angue lar relationship, whereby the cutting tool is of more or less pointed formation and cuts the thread on both sides of the groove. There is ac- 'cordingly no opportunity to provide side rake extending from both sides or cutting edges ofthe pointed tool. This results in thechips coming off from each side or edge of the tool, meeting over the top of the tool and immediately becoming bound and wedged together with the result that the tool tears the work making the thread rough and uneven.

This situation is particularly true in. connection with the softer metals, such as aluminum, copper etc., due to the characteristics of these metals to rag and tear during the cutting operation unless the tool is ground with top or side rake extending at a very appreciable angle. For example, I have found that cutting tools ground with a rake of forty-five degrees produces a much smoother cut in metals such as aluminum and its alloys, than do tools ground with a conventional angle of rake used in iron, steel an like metals.

Accordingly, the problem of cutting a thread in or on metals such asalum-lnum and copper presents even greater difliculties than the threading of iron, steel, and the harder metals. At the present time, it is attempted to overcome this situation by taking very fine cuts and passing the tool a number of times over the work. This not only consumes a considerable amount of time, but the thread, regardless of how many times the tool is passed over the work, is never smooth and uniform because there is no satis- I ness.

and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention, reference is made to the accompanying drawing in which like characters designate corresponding parts in all the 5 views.

Figure l is a sectional view of a threading tool and holder therefor involving my invention.

Figure 2 is an end elevational view of the threading tool and contiguous portion of the m holder lookingto the right Figure 1.

Figure 3 is an enlarged-fragmentary "view, of the cutting portion of thecutters shown in Figure 2. y

Figure 4 is an enlarged fragmentary detail 15 view taken on line G- i, Figure 2.

Figure 5 is an enlarged diagrammatic view showing the relative formation of the cutters arranged in superimposed position.

The cutters here shown are of disk formation 20 secured together as a unit and carried by a suitable holder. The cutters consist of disks Ni, ii, i2, I3 and I4. The cutters it, it and liars in the'nature of roughing cutters, and the cutters I 3 and It are finishing cutters. It will be apas parent as the description proceeds that the cutters may be of any general formation. I prefer the disk formation inasmuch as it is more economical than others. It 'will also be apparent that the roughing cutters Ni, ii and I? may be 30 formed of one integral piece and likewise the finishing cutters i3 and it. I

The disks It to it are'turned to the-proper size and the periphery turned to the proper formation as in the case of conventional circular form cut- 35 ters. v The disks are subsequently machined or ground oi as at I5to form a cutting portion. Thereafter, it is only necessary to grind the top surface of the cutting portion until the entire periphery of the disk is used up. 40

It will also be understood that in the event separate disks are used to form the roughing cutter, and separate disks are used to form the finishing cutter, the thickness of the disk will be determined by the pitch of the thread to be cut. For example, if. an eight pitch thread is to be cut, the individual disk will be $4; ,of an inch in thick The disks Ni, ii and I2, constituting the roughing cutters, are arranged to progressively cut the thread to full depth, as indicated in Figure 1, and more clearly in Figure 4. The included angle of the/cutting edges leis slightly less than the included angle of the thread to be ,cut. In other words, the grooves of the thread cut by the roughing cutters Ill, H and I2 is of less width than the groove of the finished thread. That is, the roughing cutters are so formed as to leave some material to be removed by the finishing cutters. The roughing cutters are formed with top rake ll, see Figures 2 and 3, the angle shown being substantially forty-five degrees, which has been found most suitable for certain aluminum alloys. The base of the cutting portion of the disks H3, II and I2 is ground circular as at E8, and after the cutters are assembled this surface is ground on an angle of approximately fifteen degrees extending in direction opposite from the finishing cutters iii, It, as more clearly shown by the surfaces I9, and 25, Figure 3. This surface aids in disposing of the chips formed by the cutting surfaces of the disks III, II and I2. However, the actual cutting surfaces of the roughing cutters are not provided with side rake and accordingly, the thread pro,- duced by these cutters is rough and uneven as is the case with conventional threading tools as previously referred to.

The finishing cutters I3, it are so formed and arranged that each cuts one side only of the thread. 22 designates the cutting edge of the cutter I3, and 23 the cutting edge of the cutter I3. These edges 22, 23 extend radially from the work and the included angle between the edges 22, 23 is complemental to the included angle of the finished thread being out. The cutters l3, H3 further distinguish from the roughing cutters in that they are provided with side rake extending from each of the. cutting edges 22, 23 transversely across the cutters and preferably this rake is ground to extend at right anglesto the cutting edges. That is, the surfaces 2%, 25 of the cutters l3 and M extend-downwardly from the edges 22, 23, the lines 26, 2'! indicating the inner wall extending upwardly from these surfaces and also indicating that the surfaces are ground perpendicular to the edges 22, 23. Also, I prefer that the cutters i3, I4 do not extend entirely to the bottom of the groove cut by the roughing cutter l2.

The relative form of the cutters is illustrated in the diagram Figure 5, the cutter Iii-ending at 23, the cutter II ending at 29, and the cutter l2 at 30. The sides of these cutters I0, II and I2 are indicated by the dotted lines at IS. The finishing cutters I3, I4 terminate at 3!.

The arrangement shown is for cutting external right hand threads and the tool is accordingly moved to the left during the cutting operation. The cutters I0, II and I2 successively ensage the work and groove the same to the full depth. Subsequently, the cutter. I3 engages the work. However, only the edge 22 thereof engages the left hand side of the rib of the thread and subsequently the edge 23 of cutter it engages the opposite side of the thread. Due to the fact that the cutters I3, I4 are formed with an appreciable side rake, the opposite edges 33, 35 extend at a lesser angle than the edges 22, 23 and accordy, that the chip removed by the edges 22 and 21-3 is neatly sheared from the work and is permitted to pass down the surfaces, 25 without any interference. Accordingly, one pass of the tool will produce a smooth, even and uniform thread which excels the more costly milled thread in that there are no waves or cutter marks on the surface of the thread.

In high pressure oil and gasoline lines, where it is necessary to have an absolutely perfect thread in order to effect a liquid tight joint, the

do not engage the thread. The result isserrations between the stem and the shank of the thread to proper form, said latter portion encased milled thread is not satisfactory due to the waves or cutter marks produced by the milling cutter.

The cutters Ill, II, I2, I3 and i in combination with the holder shown in Figures 1 and 2, form a particularly efficient threading tool and 5 one which may be quickly and conveniently adjusted after grinding operations. This holder consists of a shank member 40 provided with a transversely extending internally threaded bore to receive a sleeve 4i which is also threaded internally to receive a stem on which the disks or cutters are mounted. One end of the stem is provided with a shoulder 52, and the contiguous portion 52 is of such diameter as to slidably re ceive the disks which are secured thereto against rotary motion by a key 45. The opposite end of the stem is formed with surfaces 35 to receive a wrench, or other instrumentality, for threading the stem into the sleeve di,

The pitch of the threads in the shank 38 and if? the external threads on the sleeve ll are of dif ferent pitch than the internal threads of the sleeve and those on the stem, and the pitch of both sets of threads extends in a direction such that the cutting pressure on the cutting disk Ill will thread the stem into the sleeve 4! and the sleeve into the shank 40 to clamp the disks between the head 42 of the stem and the side of the shank. For example, in Figure 1 both sets of threads are left hand in direction, whereby the dowrfward pressure on the cutting surfaces of the disks II! to I4 tends to rotate the disks and the stem in a counter-clockwise direction Figure 2. Acordingly, the threads on the stem being left hand, this movement causes the stem to thread into the sleeve M, and by the same token because the sleeve Iii is threaded into the shank from the opposite side, it tends to move the sleeve dl to the right Figure 1. Due to the fact that the sets of threads are of different pitch, the stem is locked rigidly to the shank 40.

This construction permits the cutters to be quickly and conveniently adjusted after a grinding operation. It will be understood that the cutting surfaces of the disks Ill to I4 are ground slightly below the center of the disks and thereafter the threading tool is adjusted so that the points of the cutting surfaces are on the center of the work. This effects front clearance for-the tool. This method of obtaining front clearance on a circular tool is conventional practise.

With the structure herein described, the disks Ill to II may be removed from the stem and ground separately on a suitable grinding arbor or fixture, the setting for the grinding operation, of course, being relatively positioned on all cutters by the keyway to receve the key 44. After the cutters are ground and again assembled on the stem, the stem may be rotated until the newly ground cutting surfaces are properly positioned and are then locked in this position by threading the sleeve 4| outwardly, or to the right Figure 1. This adjustment may be minute, due

to the fact that there are no fixed surfaces or the tool.

What I claim is:

l. A threading tool having a portion arranged to rough cut the thread and a portion to finish 70 having a pair of cutting edges, one of said edges being arranged to cut one side only of the thread, and the other edge being arranged to cut the opposite side only of the thread, said finishing portion being ground with side rake extending trans- 7 versely from one cutting edge and 3. A threading tool comprising a roughing cutter and a pair of finishing cutters, said roughing cutter being arranged to cut the thread to substantially full depth, one 01' said iinishing cutters being arranged to cut one side only of the thread, and the other finishing cutter being arranged to cut the opposite side only of thethread, each of said finishing cutters being formed with a side rake extending transversely from the cutting edge of the cutter and at right angles thereto.

4. A threading tool-comprisinga plurality of cutters secured together as a unit, said cutters being of general disk formation, a'plurality of said cutters being formed and arranged to progressively cut the thread to full depth, and a pair of said cutters being arranged to subsequently finish the thread to size, each of said last mentioned cutters cuttingon one side of the thread only, and each being formed with side rake extending transversely from the cutting edge of each cutter and at right angles thereto.

5. A cutting tool comprising a stem formed with a shoulder, a circular cutter mounted on said stem and being secured against rotation relatively thereto a holder formed withan internally threaded aperture, a sleeve threaded in said aperture, said' stem being threaded into said Q sleeve, the threads on said stem and the internal threads of said sleeve being of difi'erent pitch than the threads on the exterior of the sleeve and in said holder, said stem being operable when threaded into said sleeve to clamp the cutter between the holder and the shoulder on said stem,

the. finished thread, one of said cutting edges beingarranged to cut one side only of the. rough cut thread, and the other edge being arranged to cut the opposite side only oi the rough cut thread, said finishing portion being ground with side rake extending, transversely in opposite di rections from each cutting edge.

7. A threading tool comprising a plurality of cutters, a group of said cutters acting to rough cut the thread, and a pair of said cutters acting to finish the thread to proper form, said'group of roughing cutters being formed to rough cut the thread with an included angle less-than the included angle of the flnishedthread, said pair of finishing cutters being formed with cutting edges arranged in angular relationship, the included angle between said cutting edges corresponding to the included angle of the finished thread, one of said edges being arranged to cutone side only of the thread, and the other edge being'arranged to cut the opposite side only of the thread, and each of said finishing cutters being ground with side rake extending transversely in opposite direction from each cutting edge.

8. A'threading tool comprising a plurality of cutters arranged in a common plane extending parallel with the axisof the work, a group of being formed with a. side rake extending transversely from the cutting edge of said cutter, and

the other finishing cutter being formed .with a side rake extending transversely from the cutting. edge of'the second cutter in opposite direction to a;

the rake oi the first finishing cutter.

WILLARD a. marsh.

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