US3177508A - Set of high speed carbide chasers - Google Patents

Description

April 13, 1965 J. A. scoTT ETAL 3, 77,5

SET OF HIGH SPEED CARBIDE CHASERS Filed Nov. 1, 1962 4 Sheets-Sheet 1 23 A TTOP/VE Y.

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April 13, 1965 "llm "Uni

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April 13, 1965 J. A. SCOTT ETAL SET OF HIGH SPEED CARBIDE CHASERS 4 Sheets-Sheet 3 Filed Nov. 1, 1962 INVENTOR 2M Q BY l 5" nrroe/wsk April 13, 1965 J. A. SCOTT ETAL SET OF HIGH SPEED CARBIDE CHASE RS 4 Sheets-Sheet 4 Filed Nov. 1, 1962 INVENTOR 4&Z/

' ATTOP/V'K United States Patent 3,177,508 SET OF HIGH SPEED CARBIDE CHASERS James A. Scott, Pittsburgh, Pa, and Donald 0. Appleby,

Mentor, Ohio; said Appleby assignor to The Pipe Machinery. Company, Wicklitfe, Ohio, a corporation of Ohio, and said Scott assignor to United States Steel Corporation, a corporation of New Jersey Filed Nov. 1, 1962, Ser. No. 234,752 1 Claim. (Cl. 10120) This invention relates to high speed carbide thread cutting teeth for cutting external threads of the general character disclosed in the applications of Donald 0. Appleby, Serial No. 234,751, filed November 1, 1962, and Serial No. 234,753, filed November 1, 1962. For convenience in comparison therewith, it is shown herein as embodied in aset of three chasers of two teeth each for cutting external tapered threads having a 45 forward flank angle, a 0 rear flank angle, and flat crests and roots, its use in a set of chasers of a different number and with a different number of teeth, and for cutting cylindrical threads and for tapping being apparent from the illustrative example.

As therein more fully disclosed, the problem presented in the forming of threads at high speed with carbide chasers is the result of a combination of factors. First, generally, carbide chasers should make a positive cut at all times. Second, they are very brittle and tend to break unless properly loaded. Thirdly, due to the high speed, loading with chips must be avoided and free access of coolant must be permitted. These latter problems are difficult of solution because of the rapid accumulation of chips at high speed and the resultant high heat developed. Loading of chips tends not only to greatly increase the stress load on the chaser teeth and the power requirements for forcing the teeth on their cutting strokes, it also results in the coolant used being dissipated largely on already formed chips and not reaching as effectively as desired the teeth and the metal at the cutting edges of the teeth. The problem, therefore, is to cut at high speeds while providing ample space for chips and their ready removal by the coolant, without packing, and to assure that the final surfaces originally cut by the teeth are not marred by chips or rubbed by succeeding teeth in any way thereafter.

The manner in which these combined results are obtained will become apparent from the following description, wherein reference is made to the drawings, in which.

FIG. 1 is a diagrammatic front elevation of the rotary spindle head with the set of chasers of the present invention installed therein;

FIGS. 2 and 3 are an elevation of the forward face, and a left end elevation, respectively, of the first operating chaser of the set;

FIGS. 4 and 5 are a front elevation of the forward face, and a left end elevation, respectively, of the second chaser of the set;

FIGS. 6 and 7 are a front elevation of the forward face, and a left end elevation, respectively, of the third chaser of the set;

FIG. 8 is an enlarged diagrammatic illustration showing, in superposed relation, the cuts made by the various teeth of the chasers of the set; and

FIGS. 9A through 9F are enlarged fragmentary illustrations showing the cuts made by the teeth, respectively.

Referring to the drawings, the chasers are indicated at C C and C and the teeth, in cutting sequence, as 1 through 6, respectively.

The first chaser is illustrated in FIGS. 2 and 3 at C this chaser having teeth 1 and 4, respectively. The next chaser, in order of operation, is illustrated in FIGS. 4 and 5, and indicated at C and has teeth 2 and 5, respectively.

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The third chaser, in order of operation, is illustrated in FIGS. 6 and 7, at C and has teeth 3 and 6, respectively.

Again referring to the drawings, the chasers are shown as mounted in a rotary spindle head 1 which is power driven for rotating the chasers about the common axis. The teeth of the chasers are arranged so that, in cutting sequence, the tooth 1 makes the first cut, indicated at 10, including a root portion 11, and an elongated leading portion 12. The first cut has flank ends 13 and 14, respectively. Since this tooth is of a relatively limited depth from its base to its crest, it can easily be made sturdy to resist the cutting stresses and can effectively make the cut despite the long length of the shear line and the depth of the portion 11, While providing ample space for removal of chips. It is noted that the flank ends 13, 13a, and 14 do not make a cut to the finished flank lines, indicated in dotted lines, of the thread.

The second cut is formed by tooth 2. This tooth plunges deeply into the metal toward the finished root line of the thread, as indicated at 15. This plunging cut has flank ends 16 and 17, the end 16 forming a continuation of the shear line on the forward flank formed by the preceding tooth 1, the flank end 17 being inset away from the rear flank line. The next cut, made by tooth 3, is indicated at 18. This out has flank ends 19 and 20 and root surface 21. The root surface 21 cuts to the root line of the finished thread for a substantial portion of the length of the root line in a direction endwise of the axis of the thread. The surface 19 forms a continuation of the surface 16 formed by the cut 15, and the surface 20 is inset away from the flank cut 17. Thus along the surface exposed at the leading flank of the thread, between adjacent teeth, the leading flank of the tooth 2 rubs against the surface and, in turn, the tooth 3 rubs against the forward flank surfaces 13a and 16. While this is objectionable, the teeth do have very substantial lengths, endwise of the thread axis in relation to their dimensions radially or toward the root of the thread. At the same time, ample space is provided for accumulation and escape of chips.

Having made three successive plunging cuts, the next, or fourth, cut is by the tooth 4 on the chaser C This cut is a simple flank cut, as indicated at 22. The fifth cut is made by tooth 5 of chaser C and is another flank cut, indicated at 23. Thus far none of the finished surfaces of the thread have been formed, except the root.

The last one or sixth cut 24a, 24b, and 240, is an interrupted flank cut, including the portion 24a on the forward flank and the portion 2412 on the rear flank, and the portion 240 on the crest of the trailing tooth. The cut, indicated at 25, also includes portions 24d and 24a of the root between the adjacent thread flanks.

As a result of this structure, a quick plunge cut in three successive steps can be made entirely to the root of the thread, the last plunge finishing most of the root. While each of these cuts removes a substantial amount of material, adequate space for the chips to be flushed out by coolant at each cut is provided. Furthermore, no portion of the final surface of the thread, except the root, is in any manner engaged by a tooth after the initial formation of the thread surface. The final out has a long interrupted shear line, but nevertheless adequate space to permit the coolant to flush away chips is provided. Each tooth can be large, and long lengthwise of the thread axis, and thus be strong enough to withstand the cutting stress imposed by the long shear line.

It has been found that, with this structure, considerable increase in life and improvement in quality can be obtained over the speed and quality obtained by the structure of the above identified application.

The sets of chasers herein are for cutting threads having a wide crest and wide root, as distinguished from I a i 7 3,177,508

conventional V-shapedthreadswhich have relatively sharp crests. and. narrow roots, for. instance, such. as produced;

by the intersection'of planar flanks at 60 to each other, and the words wide crest; wide root as used in the elai'msrin referring, to'the. threads are: meantto I exclude-v theconventional Wshapedthreads, inasmuch as the prob: lemswin; connection with: the: latter. are; totally different fronithose in connection with the wide crest,v wide root type 0 ad a a 4 Having thus described-our inventiomwe claimz.

A set of thread cutting; chasers, said set consisting of three high speed carbide chasers eachtwithtwo teeth only,

said zchasers being adapted to be mounted in a rotary,

spindle head" inradiall-yand: circumferentially spaced relation to eachother about the" axis of rotation of the head for. co-rotation of the chasers by the head about said axis and for concurrent advancement and'retraction of thetchasersrelative to the axis: for cutting on a cylindrical; member, coaxialtwith therspindl'e head, of an external-,wide crest, wide root, tapered thread, said chasers having their teeth shaped-and. arranged in'the order of cuttingas follows:

, 1st, 2nd, \and- 3rd teeth with said first toothyhaving at trailingportion and'a leadingportion of less height; than the trailing portion,' the radial heights of said;

i trailing; portion,'the 2nd tooth, and the 3rd tooth;

respectively, being, intheorder enumenated,gpro'-.- gressively shorter in a direction endwise ofthe axis and progressively, greater in height radially of the axis, and-having trailing flanks inset progressively:

relative toe'ach other, leadingflankssloping inwardly from base? to crest sothat the axially innermost-point on theleading flank. ofeach is coincident with the! axially outermost point; ofits successor, for making cessor, and with the leading flanks ofthe; root cutsforming; a continuous surface sloping inthe tnailing direction from crest to trough-of the thread; the major portion-ofthe'crest of" the 3rd tooth conform-7 ing :to: the major: portion ofthe finished root line. of: the. thread the flanks ofthe lstztoothibeing inset from the finished flank lines of the thread; a a. 4th? tooth. which; is; of. iaiheight greater than thatvof said tnailing portion of the: 1st: tooth: and less; than that: of,the 2nd tooth, and having; atrailing flank insetfromthe'rtrajlingflanks of said 2nd tooth and said-portion of the 1st: tooth and: having a leading flank passing, through a point between the radially innermost and-outermost ends of the; leading flank of the" 2nd tooth: and sl'oping fromftheucrest ofthe? 4th toothin-rtheleading direction; toward the base 7 i v (E. of the 4th tooth so as to 'lie forwardly fromsaid point and-from the leading flank ofsaid trailing portion of the first tooth throughout the radial extent of said leading flank of'the 1st portion, for making an uninterrupted flank cut on the trailing flank only ofthethread; a 5th toothxof greater height than that of me; 2nd tooth andf'less than that'of the '3rd-toottr; andhaving:atrail ing flank inset from the tra-iliirg'flankof the, 1st, 2nd, 'Bfrdl and 4th teeth and a leadingl'fianl'c sloping in the leading direction from itscrest toward the, base of the Sthxtoothuand intersecting {the leadingflank of the 3rd tooth scxasito lie .forwardlyofqthe leading'flank of the 4th tooth, for making a second uninterrupted flank'cut on the leading flank'only of the thread; a 6th tooth of substantially the-same height asthe 3rd tooth; andhaving leadingand trailing flanksoutset, endwise ofthe axis, from the' correspondingfianks of said: trailing portionof the' 1st toothandfrom the corresponding flanks-oh the Zndthrough: 5th" teeth, and conforming tothe finished trailing and leading flanks, respectively, of the finished thread, said 6th tooth having a wailing-portion.extending inthe trailing direction from the lowestpoint on its rear fl'ankpredominantly endwise of: the-axis andforrning with the' rear flanh'of the 6th tooth a, continuous cutting edge conforming to the finished Ieadingfl'ank and 1 contiguous crest of thE-th-FCadQ aHd said lead-ingportion of the lsttooth2extending from the lowest point on the leading flank ofthe trailing portion of the l'st ito'oth in the leading direction ge'nerallyendwisex of -the axis and: forming with' theile-a'ding'flankof said trailing-1 portionya'continuous cutting edge extending-:in the. leading ldirectionbeyond the leading fl'ank 'of the thread. and being'of a radia-l' height less 7 than thezhei ght' of 'the -trailing pontion of the- 6th tooth, for. makingatrue-up cutin strata of the 'pipe outwardly beyond the thread so that the: 3rd tooth- I 1 makes the: final cut on .at leastthe'major portionof cut of the remainder of 1 the: thread;-

Reference s. Citedthy the Examiner;

UNITED STATES AND E R., J-UI-IASZ, Primary Examiner,

-therthread trough andtheoth tooth: makes the finish

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