US2739496A - Gun drill - Google Patents

Description

March 27, 1956 J. FLElscl-IER 2,739,496

GUN DRILL Filed June 30, 1952 United States Patent GUN DRILL John Fleischer, Royal Oak, Mich., assignor to National Twist Drill & Tool Company, Rochester, Mich., a corporation of Michigan Application June 30, 1952, Serial No. 296,426

1 Claim. (Cl. 7768) The invention relates generally to drills and refers more particularly to improvements in relatively long drills commonly known as gun drills.

It is an object of this invention to provide a gun type drill wherein the cutting edge, or edges, are carried by a tip which is not only formed separately from the shank but, in addition, is readily removably secured to the shank of the drill.

As a result of the foregoing, manufacture and maintenance of the drill is greatly simplified. In practice the tips of the drills require considerably more time to produce than the Shanks and in accordance with this invention it is possible to produce the tips in their various required sizes separately from the Shanks. Thus, it is practical for a manufacturer to maintain an inventory consisting of a number of tips of different sizes so that when a drill of standard Size is required it is only necessary to make the comparatively simple shank. Also with the present invention, manufacturers may ship tips to users for installation on shanks in their possession. Hence, the tool cost is reduced because the user is not required to purchase a shank each time it is necessary to replace a drill tip. Moreover when the cutting edges on the drill tip become worn to an extent requiring resharpening, the user in the matter of minutes may remove the tip from the shank. Thus sharpening of the cutting edges on the drill tip is greatly facilitated as it is much simpler to handle the relatively short drill tip than it is to handle the complete drill.

It is still another object of this invention to provide a connection between the shank and drill tip which is not only readily detachable but which assures a strong, rigid tie between the shank and drill tip. Thus all of the numerous advantages of a readily detachable connection between the shank and drill tip are obtainable without sacrificing accuracy.

The foregoing as well as other objects will become more apparent as this description proceeds, especially when considered in connection with the accompanying drawing, wherein:

Figure 1 is an elevational view of a drill embodying the features of this invention and showing the same in operative relation to a workpiece;

Figure 2 is an end elevational view of the drill shown in Figure l;

Figure 3 is a cross sectional view taken on the line 3 3 of Figure l;

Figure 4 is a sectional View taken on the line 4-4 of Figure 3;

Figure 5 is a fragmentary perspective view of the inner end of the drill stern, and

Figure 6 is a fragmentary perspective view of the inner end of the drill bit or tip.

For the purpose of illustrating the present invention, l have selected a gun type drill of considerable length comprising a shank or stem 10 and a bit or cutting tip 11. The stem 10 has a reduced part 12 at the outer end and the inner end is formed with a generally V-shaped recess 13 having the opposite side walls 14 converging toward the axis of the stem and havingA a base 15. The base 15 extends substantially perpendicular to the axis of the stem and connects the radially inner edges of the side walls 14.

The bit or cutting tip 11 is fashioned with a projectionv 16 at the inner end having'opposite side walls 17 converging toward the axis of the cutting vtip and connected by an end wall 18 which extends perpendicular to the axis of the cutting tip. The projection 16 on the inner end of the cutting tip 11 is fashioned to extend into the recess 13 at the inner end of the stem 10. The walls 14 and 17 are predeterminedly fashioned to respectively inti-` mately engage one another and form driving faces in is secured to the stem 10 by a fastener element 19 having a head 20 and a threaded shank 21.

The fastener element 19 is insertable through a bore 22 extending for the full length of the cutting tip 11' and, for reasons to be more fully set forth, offset lat erally from the axis of the cutting tip 11. vThe bore 22 is reduced at the inner end of the cutting tip 11 in order to provide a shoulder 23 against which the head 20 on the fastener element abuts. The reduced portion of the bore 22 opens through the wall 18 on the projection 16 at the inner end of the cutting tip 11, and the stern 10 is fashioned with an aligned bore 24 which is threaded.

The shank 21 of the fastener element 19 extendsr through the reduced portion of the bore' 22 and thread*` ably engages the bore 24. The enlarged portion of the bore 22 is of ample diameter to freelyreceive the head 20 on the fastener element 19 and to also receive a suitable socket type wrench, not shown herein. present instance, the head 20 on the fastener element has a. socket 26 which cooperates with the Wrench to enable manipulating the fastener element 19. With the above construction, it will be noted that the fastener element 19 elfectively clamps the driving faces 14 and 17 together in a manner such that the fastener element is relieved of any driving stress. Although when the stem 10 of the drill is fastened to the cutting tip 11, the drill functions just as effectively as if it were made of one piece,

nevertheless, it will be apparent that the cutting tip 11 may be quickly removed from the stem by merely disengaging the fastener element 19.

By forming the cutting tip 11 separately from the stem 1l) and removably securing the two parts together,

numerous advantages are obtained. For example when the cutting tip 11 requires sharpening it may be readily removed from the stem 10 and consequently the sharpening operation is greatly simplilied. Also, when the cutting tip becomes worn to such an extent that it must be discarded, replacement may be readily accomplished without replacing or reworking the stem 1t). Moreover,

the foregoing structure renders it possible for the manucircumferentially of the cutting tip 11 and extend in theV direction of length of the latter. The outer surfaces of the inserts 27 project beyond the outer surface of the cutting tip and are arranged on a circle having a diin the ameter greater than the. outside diameter of the stem I0. lt has been stated above that the aligned bores 22, 24 are offset with respect to the axis of the drill and the and cutting; tip, ll respectively. The groove; 30 extends for the full length of the cutting tip' 11 and the; groove 29v has a length at least as great as the depth of?. t-he hole: to

be` drilled. i

The side wallsl of the chip. ute ZSLconx/ergc to a central opening or channel 31 which extendsaxially through the cutting tip 11, and` stem 10,. and coacts with anv inserted cutter 32 to form an undrillecl centerrod 33 (Fig.v l) fromthe work beingy drilled for guiding the drill during the Idrilling operation. In detail, the: cutter insert 32 is located at the outer endv ofthe'tipll' and extends along one wall of the groove 30' in the' tip 11. The insert 32 has a cutting-edge 34 at the radially outer edge thereof for cutting the hole in the workpieceand has a cutting edge 35 at the radially inner edge thereof which. intersects the openingl to'forrn the'rod33. l

It will also be noted from the drawing that the stem A10 and cutting tip 1l are formed with aligned passages 35. The passage 35 in. the tip 11 extends for the full length thereof and suitable means isA provided for introducing a coolant into the passage 35 at the outer end of the stem 10. It will be noted from Figures 2 and 3 of the drawings that the passage 35 is offset laterally from` both the openings 31 and aligned bores 22, 24 so as not to appreciably -Weaken the structure of the drill.

It will be apparent from the foregoing that we have provided a gun type drill havingl all of the desired structural features and at the same time renderingit possible to quickly detachably secure the cutting tip to the stem. The detachable mounting is of a nature that it does not interfereV with the chip flute 28, opening 31 for producing the drill guiding rod 33, and the coolant passage 35.

What I- claim as my invention is:

A drill having an elongatedstem. part, a separable cutting tip part aligned with said stem part' in end-to-end relation, one of said parts having a generally V-shaped recess extending entirely across the inner end thereof, the converging sides of said recess being symmetrically arranged relative to the drill axis to provide driving faces, a projection on the inner end of the other part received in said recess, said projection having converging sides arranged symmetricallyI relative to the drill axis to provide driving faces disposed. to have intimate surfaceto-surface engagement with the driving faces` ofsaid recess, thereby to alignsaid parts and to provide a driving' connection therebetween, the tip' of said projection being spaced from the base of said recess in order not to interfere withclamping the. driving. faces of said" parts `in intimate surface-to-surface engagemenh, a first bore in said cutting tip part extending from one end thereof to the other and having a shoulder adjacent the inner end of said cutting tip part, a second bore in said stem part aligned with the rst bore andY being internallythreaded, a fastener elementffor removably connecting saidv parts and for clamping said driving faces inintimate surfaceto-surface engagement, said` fastener element having a head seated against said shoulder andl havingia threaded shank threadedlyengaged with thesecond bore, said bores being` laterally offset from the drill axis, a groove in said cutting tip part providing a chip flute extending the full! ,length thereof, a groove in said stem part pro viding al chipV flute extending lengthwise thereof in continuation of4 the chip ute inJ said cutting, tip part, and

aligned central channels in said parts extending along.

the axis of said drill-,and communicating with therespectiveA chip utes.

References Cited in they file of this patent UNITEDl STATES PATENTS 1,461',462 Smith et al. July 1D, l92'3` 1,746,716 Sasse Feb. 1l, 1930 2,325,535 Nordberg July 27, 1943 2,418,021" Fleischer Mar. 25, 1947

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