Drill with trimming attachment

Abstract: A drill and trimming attachment assembly is disclosed for drilling holes with beveled top openings in a work piece. The assembly includes a drill shaft with at least one longitudinally extending groove formed therein. A trimming attachment suitable for clamping to the drill shaft is also provided to form a beveled recess at the top of a hole formed by the drill. The trimming attachment includes a body and a trimming blade having base and arm portions. The base portion of the trimming blade is detachably secured to the body, and the body is arranged to be removably journaled about and clamped to the shaft of the drill such that an edge of the arm portion or the trimming blade is closely received by the groove. Thus, during use, the groove carries at least a portion of the load acting against the trimming blade.

Description: This invention relates to a drill having a trimming attachment for forming a frusto-conical shaped recess at the opening edge of the hole formed during drilling. Fig. 4 shows a known drill trimming attachment. As seen therein a trimming attachment 33 is attached to the shaft 32 of a drill 31. The trimming attachment 33 consists of a cylindrical body 34 that is clamped to the drill 31 and a trimming blade 36 for trimming the opening edge of a drilled hole 37 to provide a frusto-conical tapered surface 28. The inner surface 35 of the trimming blade 36 abuts against the shaft 32 of the drill, while the base thereof is supported and fixed in the body 34. Other generally known drills with trimming attachments generally have the drill and the trimming attachment formed as an integral body. Yet another has a trimming blade formed integrally with the bottom of a cylindrical body that is clamped to the drill. When a work piece is drilled using any of these types of drills, the drill can form a hole 37 and also chamfer the opening edge of the hole 37 to provide a frusto-conical tapered surface 38. In the drill with a trimming attachment of the type shown in Fig. 4, the trimming blade 36 is fixed to the shaft 32 of the drill by allowing the inner surface 35 of the trimming blade 36 to abut against the circumference of the shaft 32 and by supporting and fixing the base thereof in the body 34. Accordingly, the tip portion of the trimming blade 36 cannot be secured to the shaft, although the base thereof can be securely fixed. Thus, the trimming blade 36 is sometimes flexed or deflected by the force applied thereto during the chamfering operation. If a work piece is drilled in such state, the work piece suffers a poor appearance at the tapered surface 38, since the opening edge of the hole 37 cannot be chamfered neatly. On the other hand, drills having a trimming cutter formed integrally therewith, by shaping a piece of bar-like material suffers a problem in that the production cost is high since machining thereof is very difficult. On the other hand, the drill with a trimming attachment of the type having the trimming blade formed integrally with the body 34 at the bottom thereof also suffers a problem in that it requires a number of bodies 34 corresponding to the number of drills with different outer diameters since the outer diameter of the drill which is acceptable in the body 34 is limited, again leading to a high cost of parts. DE-C-3610016 discloses a drill having a trimming attachment removably clamped to a shaft of the drill for forming a bevelled recess, as defined in the preamble of claim 1. Accordingly, it is a primary object of this invention to provide a drill with a trimming attachment that can firmly be secured on the drill and which can be produced at a low cost and with reduced part cost. According to the present invention there is provided a drill for forming a hole in a work piece and a trimming attachment removably clamped to a shaft of the drill for forming a bevelled recess at the top surface of the hole, the trimming attachment including a body and a trimming blade having base and arm portions, whereby a longitudinally extending groove is formed in the shaft of the drill; the base portion of the trimming blade is detachably secured to the body; said body is arranged to be journaled about and clamped to the shaft of the drill such that an edge of the arm portion of the trimming blade is closely received by said groove such that during use, the groove carries at least a portion of the load acting against the trimming blade; the drill being characterised in that the body includes a plurality of separate blocks and a plurality of bolts for coupling the blocks together; and the trimming blade having a hole extending through the base portion and being secured by a said bolt inserted through the hole to the body at a position between the two of the blocks. In one preferred embodiment, the drill haft includes a plurality of helical flutes and a plurality of longitudinally extending grooves. The grooves are defined at axially and circumferentially staggered positions about the periphery of the shaft. The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with the objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: Fig. 1 shows in front view one embodiment of this invention, illustrating a drill having a trimming attachment clamped thereto; Fig. 2 shows a side view of the drill shown in Fig. 1 having a trimming attachment clamped thereto; Fig. 3 shows an exploded perspective view of the trimming attachment shown in Fig. 1; and Fig. 4 shows a side view of a prior art trimming attachment. An embodiment of the drill with a trimming attachment according to this invention will be described referring to Figs. 1 to 3. As shown in Fig. 1, the drill with a trimming attachment consists of a drill 1 and a trimming attachment 2. As shown in Fig. 3, the trimming attachment 2 consists of a cylindrical body and a trimming blade 4 for trimming the opening edge of a drilled hole. The body 3 is divided into three parts so that the inner diameter thereof may be changed and that the base of the trimming blade 4 may be secured therebetween. The blocks 5, 6 and 7 constituting the body 3 each have a threaded hole 11, and these blocks 5, 6, 7 can be combined by screwing bolts 8, 9 and 10 into the respective threaded holes 11. The trimming blade 4 is an elongated and thin plate. The base of the trimming blade 4 has a through hole 12 at a position corresponding to the threaded hole 11, while the tip thereof has a cutting edge 13 formed at a predetermined angle (< 90°) based on the axis L shown in Fig. 1. The trimming blade 4 is fixed in the body 3 being held between any arbitrary two blocks and secured by the bolt inserted through the through hole 12. As shown in Fig. 2, the shaft 14 of the drill 1 has a predetermined length of three grooves 16, for catching the inner surface 15 of the trimming blade 4 therein, formed along the axis L at staggered positions. These grooves 16 have a sufficient depth (about 0.5 mm in this embodiment) and a width approximately the same as the thickness of the trimming blade 4 so that the inner surface 15 of the trimming blade 4 may firmly be secured therein. Next, action of this embodiment will be described. The three blocks 5, 6, 7 are combined by three bolts 8, 9, 10 with the base of the trimming blade 4 being supported between the two blocks 5, 6 to fix the trimming blade 4 to the body 3. The inner diameter of the body 3 can be adjusted by tightening or loosening the bolts 8, 9, 10. The bolts 8, 9, 10 of the trimming attachment 2 are loosened a little to provide an inner diameter greater than the outer diameter of the drill 1, and then the trimming attachment 2 is applied to the drill 1. After the inner surface 15 of the trimming blade 4 is engaged in the groove 16 of the drill 1, the bolts 8, 9, 10 are tightened again, and thus clamping of the trimming attachment 2 to the drill 1 is completed. When drilling and trimming is carried out using the drill 1 having the trimming attachment 2 clamped thereto, the drill 1 is first mounted to the chuck (not shown) of, for example, a drilling machine. Then, the free end of the drill 1 is abutted against a work piece 19 while the drill 1 is rotated in the rotational direction X, whereby a tapered surface 18 can be formed along the opening edge of a hole 17 as it is formed by the drill 1. According to the above embodiment, the trimming attachment 2 is clamped to the drill 1 with the base of the trimming blade 4 being supported by the body 3, while the inner surface 15 of the arm portion of the trimming blade 4 is received by the groove 16 of the drill 1. Thus, flex or deflection of the trimming blade 4 to be caused by the force applied to the side face thereof can be reduced to achieve trimming more neatly than by the conventional drill. Additionally, damage of the trimming blade 4 can be prevented. Moreover these three grooves 26 formed axially at staggered positions allow wide selection of the position of fixing the trimming attachment 2 along the axis L, so that trimmed holes 17 having a variety of depths can be formed. It should be noted that the above embodiment can be modified or varied as follows: 1. The number of the blocks in the body 3 of the trimming attachment 2 may be increased or decreased. 2. The number of the grooves 16 may be increased or decreased.

Claims: A drill for forming a hole in a work piece and a trimming attachment removably clamped to a shaft of the drill for forming a bevelled recess at the top surface of the hole, the trimming attachment including a body (3) and a trimming blade (4) having base and arm portions, whereby a longitudinally extending groove (16) is formed in the shaft of the drill; the base portion of the trimming blade (4) is detachably secured to the body (3); said body (3) is arranged to be journaled about and clamped to the shaft of the drill such that an edge of the arm portion of the trimming blade (4) is closely received by said groove (15) such that during use, the groove (16) carries at least a portion of the load acting against the trimming blade (4); the drill being characterised in that: the body (3) includes a plurality of separate blocks (5, 6, 7) and a plurality of bolts (8,9,10) for coupling the blocks together; and the trimming blade (4) having a hole (12) extending through the base portion and being secured by one of said bolt inserted through the hole to the body at a position between two of the blocks. The drill according to claim 1, wherein the trimming blade (4) has a cutting edge (13) formed at an acute angle relative to a rotational axis of the drill. The drill according to claim 1, wherein the shaft has a plurality of longitudinally extending grooves (16) defined at axially and circumferentially staggered positions about the drill shaft, and the trimming blade (4) is selectively placed in one of the grooves.

Inventors: OMI SHOHEI C O OMI KOGYO CO LT, OMI TAKASHI, OMI, SHOHEI, C/O OMI KOGYO CO LTD., OMI, TAKASHI
Applicants: OMI KOGYO KK, OMI KOGYO CO., LTD.
Application year: 1991
Main classification: B23B51
IPC codes: B23B51