Untitled record

867010

The subject of the invention is a twist drill with dovetail-shaped head made of high-speed steel.

In the previous drills of this type either no tension connection between the head and shaft is present, or the connection is such that the dovetail attachment adjacent end faces of the parts are pushed out of contact with each other. This makes the connection a more or less unsafe, and the dovetail is heavily stressed twisting and bending, so that it tears off easily.

The invention provides a remedy that the mentioned end faces in the longitudinal direction of the dovetail axial suit, so that they clamp the dovetail and also each other. As a result, these large surfaces act as a kind of friction clutch, which transmits a large part of the rotational force and thereby relieves the dovetail accordingly.

In the drawing, two embodiments of the subject invention are shown schematically.

Fig. 1 is a front view of the compound drill,

Figure 2 is a front view of the exploded parts,

Fig. 3 is a side view of the exploded parts,

FIG. 4 shows a plan view of the shank according to FIG.

Fig. 5 is a front view of a second embodiment,

Fig. 6 is a front view of exploded parts,

Fig. 7 is a side view of Fig. 6 and Fig. 8 is a plan view of the shaft according to Fig. 5.

The drill tip α engages with the dovetail b in the dovetail groove c of the shaft d. According to the invention, the dovetail attachment adjacent faces e and / of the parts α and d are not directed at right angles to the longitudinal axis of the drill, but have in the longitudinal direction of the dovetail suit, so rise as shown in Fig. 2 from front to back or as shown in Fig. 3rd from right to left. Thus, if the parts are pushed together by means of the dovetail guide, so on the one hand, the dovetail b against the walls of the groove c is pulled firmly outward, and on the other hand, the surfaces e and / are pressed tightly together.

The embodiment according to Fig. 5 to 8 differs from that according to Fig. 1 to 4, characterized in that in her the aforementioned end faces are not flat, but lead together with prismatic overlap, whereby the compound is further improved. The forehead of the shaft d thus consists of two projections whose end faces are formed by two roof-shaped abutting surfaces e 'and e ", which correspond to mating surfaces f and f" at the tip. Incidentally, the pitch of the faces e 'and e "and f and f" are the same as those of the faces e and / of Figs. 1 to 4.

By this training, a collision of the teeth of the bifurcated body d is counteracted by the overlap by the body α from the outside.