US2392823A - Broach - Google Patents

Description

F. J. LAPOINTE' BROACH Jan. 15, 1946.

Filed May 10, 1944 2 Sheets$heet 1 Jan. 15, 1946. F J, LAPO E 2392,8233

BROACHI Filed may I0, 1944 2 Sheets-Sheet 2 IN VENTOR.

Patented Jan. 15, 1946 BROACH Francis J. Lapointe, Ann Arbor, Mich., assignor to American Broach & Machine 00., Ann Arbor, Mich., a corporation of Michigan Application May 10, 1944, Serial No. 534,848

8 Claims.

This invention relates to the art of broaching, and it is particularly concerned with a broach comprising a body with multiple cutters mounted thereon.

One object of the invention is to provide a novel and improved broach having a plurality of individual cutters mounted in a supporting base or body.

Another object of the invention is to provide a broach comprising a body of relatively soft metal with a plurality of individual cutters of wear-resisting metal mounted therein.

A further object of the invention is to provide a broach composed of a block or base having a plurality of holes or sockets formed therein, spaced apart and arranged in rows and provided with a plurality of individual cutter elements secured rigidly in said holes or sockets but individually removable for repair or replacement.

It is also an object of the invention to provide a broach comprising a body with individual cutters mounted therein in rows and spaced apart from each other, and with the cutters of one row sta gered with respect to those of an adjacent row so that the broach, as a whole, is adapted to operate upon an entire continuous surface.

More specifically, the invention is concerned with a broach comprisin a body block of relatively soft metal, with a plurality of holes formed therein in rows and spaced apart, and with slots cut in the marginal portions of the body at the ends of said rows, together with individual cutters set in said holes and in said slots and brazed therein, the cutters being arranged in staggered relation to insure operation upon an entire continuous surface and the spaces between the cutters serving as chip breakers in the operation of the broach.

Other objects and advantages of the invention will appear from the following description taken in connection with the drawings in which:

Fig. 1 is a plan view of a broaching tool or unit embodying this invention. I

Fig. 2 is a side elevation of the same.

Fig. 3 is a transverse sectional view taken as indicated at line 33 on Fig. 1.

Fig. 4 is a perspective view of an individual cutter before insertion in the body of the broach.

Fig. 5 is a plan view of a modified form of broach unit'embodying the invention.

Fig. 6 is a sectional view of the same, taken as indicated at line 65 on Fig. 5.

Fig. 7 is a fragmentary plan view of a broach, showing a modified arrangement of the cutter bits to secure a shearing cut.

Fig. 8 is a fragmentary side elevation of the broach shown in Fig. '7.

While there is illustrated in the drawings and hereinafter described a preferred form of the invention, it is contemplated that various modifications may be made by thoseskilled in the art without departing from the spirit and scope of the appended claims.

In constructing broaches of high speed tool steel the practice has been to construct a nearly complete breaching tool and apply strips of tungsten carbide tool steel thereto by brazing such strips across the face of the tool and then grinding the final cutting edges therein. This practice was not only expensive but the heat gen-- erated in the grinding would frequently cause surface cracks, and the brazing of the face pre-- sented a diflicult problem. Furthermore, with this continuous surface of the harder material: it was necessary to grind in the notches serving as; chip breakers and because of the hardness of the material this additional grinding was slow and expensive. The present construction is designed to secure the advantages of modern high speed tool steels for the broaching work without the disadvantages heretofore encountered in attempting to utilize this material in broaching tools.

As shown in the drawings, this construction comprises a body block or base I having formed in it a plurality of holes or sockets 2 arranged in rows extending transversely of the block, that is, transversely of the direction in which it is expected to move relatively to the work when employed in a breaching machine. As seen in Figs. 1, 2 and 3 the sockets 2 are formed by first drilling round holes and then breaching them to form square-cornered sockets, by using a broach in which the width is somewhat less than the diameter of the drilled holes. Individual cutters 3, shown as of square cross-section, are fitted snugly in the holes or sockets 2 and are rigidly secured therein by brazing. Preferably, at the ends of the rows of holes 2 the block I is formed with slots 4 of rectangular cross-section into which additional cutters 3 may be fitted snugly and brazed in position, the slots 6 being formed in the marginal portions of the block I because they can be conveniently machined in this form, whereas it is simpler to drill the round holes in the remaining areas of the block I and complete them by breaching as described. Either form of socket will rigidly support one of the individual cutters 3, the cutters in the slots 4 having cutting edges terminating substantially flush with the sides of the block, as shown in Fig. 1. Preferably, as shown in Fig. 2, the upper surface of the body or block I is provided with transverse grooves or channels arranged just in front of each row of the cutters 3 to afiord ample space to accommodate the chips removed by the cutting edges 3 in operation of the breach. The body block I may be secured to the supporting surface of thebroaching machine in any suitable manner, as," for example, by means of bolts engag ing threaded holes 6 tapped in the rear face of the block, as indicated in Fig. 3.

Preferably, with a breaching tool of this type of construction, the individual cutters 3 will be all of the same length, and the body I -will-be of uniform thickness, but may be mounted upon .:a tapered shim, indicated in dotted outline-at-l in Fig. 2. Thus, as each successiverow ofthecutters 3 traverses the work an additional increment of material is removed, until the required depth of .eut'has been effected. Inpractice, two or more unit breaches of the type illustrated hereinmay .be mounted in tandem -.on thetoolsupportof the .machine, .and'the. final breach. maybe supported on a shim of uniform thickness so, that its, cutters will merely clean upanyunevenness in thesurface andprovide a final finishthereon. I

Breaches of this type are not confined to single- -surface operation,.but may be mounteduponsuitable. supports. for simultaneous cutting on several ssurfaces, as,.fer example, ininternal work, eperating .-upon two, three .or four faces duringnthe .samestroke.

'As shown inthe drawings, theindividual .bits or...cutters3 are spaced apart in their rows by .distances slightly less than. the widthof each cutter. Adjacent rows are staggered with respect to each other. so that the bits of one row are aligned with the spaces in the adjacent row and slightly overlap these spaces so that two rows of bits will complete operation over the entire width of the surface. The spacing of the individual bits automaticallyprovides the equivalent of the notches which are usually cut into continuous cutting edges toserve as chip breakers, so that the material cutfrom the workwillbe subdivided into small enough pieces to clear itself readily" from the'broaching' tool. This arrangement notponly saves the time and expense incident to grindin any chipbreakers'in a unitary or'continuous cutter, but avoids setting up any strains as between adjacent cutting edges, since'in the present structure the cutters are separatetool bitsconnected only by their insertion in the same base.

In making this type of breach the body or base block isdrilled andthe holes arebroached to form square-cornered sockets; then, if the unit is to be made so as to cut over its entire width, the marginal slots '4 are also out, and may be breached so that they will fit. the tool bits? .60

within a few thousandths of an inch. Then all .the bits or cutters are inserted and secured by the brazing material shown at8, afterwhich the breach is .ground'a'll ever .to'final size and the cuttingfaces of the tool bits are ground .and backed off on top to the proper shape. :This keeps the cost of production comparatively low.

the event of injury or breakage of any of the cutting edges of the individual bits the injured bit or cutter can be spot-heated to. the brazing temperature and thenpushed out of the base so that a new bit can beinserted .in .position' to replace it. When the entire breach has .been worn and re-groundtosuch an extent thatthe cutting 7 therein by brazing.

breach can be heated to the low temperature required for loosening the brazing, and all the bits can be removed and replaced with new bits, thus salvaging the body or base of the breach for use indefinitely.

Figs.'5 and 6 illustrate a modified construction in which the individual bits or cutters [3 are set into square holes or sockets l2 in the body block H. Instead of being brazed in ,place they are secured by individual set screws which are set obliquely into the block H adjacent each socket l2 and are tapered or beveled at their inner ends for wedging contact with the bits Hi. This permits removal of any individual bit when required, and also allows replacement of all the bits when theyare-worn out.

Fig.6 also shows a modified arrangement for amounting thebroach unit on a supporting member l5 of a breaching machine. The opposite end surfaces I6 and H of the body I l are oppositely inclined, .with-a correspondingly shaped .bar i8 providingan inclined undercut surface 19 engaging-the face lfi-and-a bar 20 havingits inclined face 2| in contact with the face I! ofthe "breach body. An abutmentbar 22is :bolted in agroove. in the support, [.5 and the bar 20 is drawn into wedgingengagement between the bar-22 and the face I! when its holding screws 23 are tight- .-.ened.

iln-Figs. "Land .8 only a fragment of abase block Si is shown, but it maybe understood that the entire block-will carry several transversely disposed rows of cutter :bits 33. These bits-are shown set in-square holes which are arranged in a stepped or ofi-set-ser-ies across the baseblock 3 l, so that the row, asa whole, is inclincdto the direction uofscutting movement of the breach. .The cutting edges 33% of "the bits 33 are. ground in alignment with each other which makes them .all slightly inclined to a line perpendicular to the vdirection of cutting movementand causes them -to operate with asheari-ngcut.

. It willbe understood. that, ordinarily, the-base or body block will. be made of relatively softv .or f-mild-steel, whilethe cutter bits will .be-special tool material, suchas the tungsten carbide tipped .bits now available .-for us asalatherand pl tools. These bits are ready for useupon grinding to; shape. and-adovgnot require hardening ertem- :;pe'ring. Thus; as compared withthe cost-of. a @unitary; solid: breach of high-speed steel thereiis ausavingin cost 10f material in making. thebody :of. ordinary .soft= steel, and therekis. a :saving 'of the :labor cost involvedinithehardening and tempering of .a unitary breach. .zThetbody; is :merely "given a "normalizing 1 treatment, .or. may be left inits original condition. "Furthermorathe risk of loss arising from cracks, shrinkage, .warping and twisting ise'liminated and the special-equipment andfskill required for the hardening process may be-dispensedwith.

- I claim as my invention:

1. A breaching tool-comprising=a body-block with a plurality-of round holes spaced=at intervals 1 the-rein; said holes-having-angular grooves in their walls defining the corner portions-of square sockets, and iridividualcuttersof square cross section fitted in said sockets, respectively, and secured 2. A breaching-tool comprising a body block with aplurality of holes spaced apart therein, and individual cutters secured respectively in said "holes of the block; said cutters'being' arranged in edges are: no longer .efficient,i'then'the entireflea-pluralityof -rows-extendingtransversely of the block and being spaced apart in said rows, the space between adjacent cutters of any row being less than the width of the cutting edge of one cutter, and the cutters of each row being disposed in staggered relation to the cutters of the adjacent row opposite the spaces of the latter, and with their cutting edges overlapping the paths of the cutters adjacent said spaces respectively.

3. A broaching tool comprising a body block with a plurality of holes spaced apart therein and arranged in rows, each lateral marginal portion of the block having slots aligned with alternate rows of holes, and individual cutters fitted and rigidly secured in said holes and slots and with the cutters in the slots providing cutting edges which terminate substantially flush with the sides of the block.

4. A broaching tool comprising a body block with a plurality of holes spaced apart therein and arranged in rows, each lateral marginal portion of the block having slots aligned with alternate rows of holes, and individual cutters fitted and rigidly secured in said holes and slots and with the cutters in the slots providing cutting edges which terminate substantially flush with the sides of the block, the holes of the other rows and the cutters therein being disposed in sta gered relation to the cutters of the adjacent rows.

5. A broaching tool comprising a body block with a plurality of round holes extending in rows transversely of the block and spaced apart in said rows, individual cutters of square cross-section fitted snugly in said holes and brazed therein, said block having slots of square cross-section cut in its lateral marginal portions, and individual cutters fitted in said slots and brazed therein in alignment with the cutters in said holes.

6. A surface broach comprising a body block with a plurality of holes spaced apart therein, individual cutters secured respectively in said holes of the block, the cutting edges of all cutters being disposed at the same distance from the bottom surface of the block, and a tapered shim positioned under the block to vary the effective height of the cutters progressively from one end of the block to the opposite end.

7. A broaching tool comprising a body block with a plurality of holes spaced apart therein, and individual cutters secured respectively in said holes, said cutters being arranged in rows extending transversely of the direction of cutting movement, and each cutter of a row being oilset from the adjacent cutter in said direction of cutting movement, whereby the row as a whole is inclined to said direction.

8. A breaching tool as defined in claim 7, with the cutting edges of the cutters of each row aligned with each other and thus inclined to a line perpendicular to the direction of cutting movement of the broach, whereby a shearing cut is made by said cutters.

FRANCIS J. LAPOINTE.

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