US1662521A - Grinding machine for twist drills - Google Patents

Description

March 13, 1928.

C. KOBIS GRINDING MACHINE FOR TWIST DRILLS Filed Feb. 14. 1927 2 sheets-sheet 1 March 13, 1928. 1,662,521

c. KOBIS GRINDTNG MACHINE FOR TWIST DRILLS Filed Feb. 14, 1927 2 Sheets-Sheet 3 Patented Mar. 13, 1928.

UNITED STATES CARL KOBIS, OF BERLIN, GERMANY.

GRINDING MACHINE FOB TWIST DRILLS.

Application filed February 14, 1927, Serial No. 168,144, and in Germany February 9, 1926.

This invention relates to that type of drill grinder in which a tubular holder. into which the drill fits, and having an abutting stop to engage the conical surface of-the drill end or lip to limit its projection'therethrough is mounted with its axis inclined to an abrading surface and so as to be movable bodily toward said surfacein a direction normal thereto, and specifically my invention relates to means (which may be supplemental to the ordinary feed screw for ca'us ing such bodily movement) for producing a limited movement forward or back in the same line, the limits of which may be prcdetel-mined with a View to securing that the grinding operation is stopped just the moment the last ground conical surface terfiiinates in the center or axial line of the In thevdrawings one embodiment of the invention is shown diagrammatically.

Fig. 1 shows the drill just brought into contact with the grinding wheel before grinding the first lip, with the point of the drill lying on its center line.

Fig. 2 is the position after the first axial adjustment to the full amount of play.

Fig. 3 is the position before grinding the second'lip.

Fig. 4 shows the position after grinding the second lip.

Fig. 5 shows the eifect ofthe new device.

Fig. 6 is an elevation and partly a vertical section of the improved grinding machine,

Fig. 6 is a section taken along the line 66 of Fig. 6, parts being broken away.

Fig. 7 is a sectional front View of Fig. 6.

Fig. 8 is a plan View of Fig. 7.

In front of the grinding wheel a is the guide-casing b in a sloping position, which guide casing holds and guides the twist drill a during grinding and has at its foremost end a gaging stop member d for the conical or substantially conical lip of the drill which for the moment is not to be ground.

The drill is inserted in the casing axially in the direction of the arrow, until the free lip comes up against the gaging stop d, whereupon the turning position of the drill is ensured by the transverse gaging stop.

Then in the usual machines as also in the new machine, by means of the adjusting .spindle 7 (Figs. 68) engaging the work piece sppport, the casing 5 together with the drill a is radially adjusted against the grinding wheel until the outer surface or lip to be ground just touches the grinding wheel a (Fig. 1). The casing is then again further adjusted by the spindle f to the distance indicated at 7 (Fig. 2), which represents the grinding feed contemplated, and the drill if it has not been carried up with the casing is then pushed forward by hand within the casing up to the gaging stop at of the casing to effect grinding as in the usual machines. If, in accordance with Fig. 1, the point has lain exactly on the centre line, that is on the axis A-B of the drill and casing, then owing to the sloping position of the drill relatively to the wheel, after this first adjustment. and grinding, the point 72.

be at a distance of about 2' from the gaging stop (Z corresponding to the amount ground on the lip first ground and the amount to be ground off the second lip.

When the drill, by being pushed forward by hand in the casing is so far adjusted that its lip opposite to the gaging stop (I again contacts with the gaging stop (1 (Fig. 4), which therefore corresponds to an adjustment to the double amount 2 the point h will again be to the right of the drill axis A--B, i. e. again out of the centre position, and so on. In this way the drill is roughly ground. the grinding being effected by swinging the drill round the sloping axis py means of the hand wheel provided there- The present invention is characterized by the provision of an auxiliary device which permits, in a simple manner, the easy withdrawal for thefinal grinding by the amount of play between the lip previously ground and the stop gauge at due to such previous grinding of that lip so as not to add this to the amount to be ground oft the second lip as the bit, is again fed forward the.

casing 6 being preferably drawn back through this distance so that for the last position. as shown by Fig. 5, it returns to the position shown in Fig. 1. Then if the drill bit he placed with the lip-to be ground touching the rinding wheel, its other 11p just ground Wlll be a distance 9 from stopgage (Z and'the drill can only be forced forward for grinding this distance, when it will be stopped by engagement with stopgage (1.. The point it of the finished drill is then exactly on the centre line (Flg. 5).

The machine will now be further described.

The casing b is pivotally held on a sloping axis in the usual way, by the member The member 2' is secured to the support In mounted on the slide m. Said slide m engages by means of a slideway at its lower part with an intermediate plate 11. which is provided with a recess 1 elongated transverse the direction of motion of the slide. A pin 0 pivotally engages a block w slidable in said recess, said pin 0 being eccentrically arranged upon an eccentric p. The eccentric p is keyed atthe top into the hub or boss of a. lever g and is rotatably mounted with- .in an intermediate socket r fixed in the slide m.

The eccentricity between the pin 0 and eccentric p corres onds to the largest adjustment g for dri ls of the diameter range concerned.

In using the machine, the lever q is first brought into'the position q shown in dotted lines (Fig. 8), in which the slide on takes up its middle position with respect to the plate n. Then, by means of the spindle f, the slide at together with the plate 'n (to which it is connected by the pin 0. and eccentric p) is adjusted so far that the drill just touches the grinding wheel a (Fig. 1).

The actual adjustment through the distance g, however, is no longer done by means of the spindle f,,but the eccentric p is moved by turning the lever from the position (Fig. 8) to the position q to the left (Fig. 8; or to an intermediate position. As the p ate 1:. is then rigidly secured to the body of the machine by the spindle f, it follows that b turning the eccentric, the slide on with tie support In, the member 2', and the casing b, are moved to the left through the distance 7, i. e. they are suitably adjusted for grinding.

In this manner grinding takes place cor responding to Fig. 2, the spindle f and the lever q and consequently also the eccentrically arranged pin 0, and eccentric p retaining their positions'during the grinding, whilst through continued oscillation of the drill holder 6 around its axis, said axis being kept stationary on account of the member i, the drill is gradually ground down. until the conical or substantially conical lip contacts with its gaging sto d. The drill is then turned round througii 180 and the grinding continued in the same way until finally the rough grinding is finished. When the position is reached as shown in Fig. 4, i. e. the position prior to the final grindin the lever 1 is moved back into the position 9' and thereby the slide m together with the casing b are drawn back through the adjustment distance 7 into the position shown in Fig. 5, whereupon the point h of the drill is brought by the final grinding exactly onto the centre line.

The. end positions of the lever q and ot the ccccntrically arranged pin 0, and eccentric p, and preferably many intermediate positions, are located by a fixing device t. This fixing device may consist of notches adapted to be engaged by spring stops as shown. V

Naturally the eccentrically arranged pivot-s could be replaced by many other devices, for example by a cone, a coarse thread, or the like.

As the adjustment in previous drill grinding machines was carried out exclusively by means of the support spindle, the movement of which is practically unlimited, there is always the danger with these machines of the workman adjusting too strongly and thus grinding down the casing. This danger is eliminated in the new machine, as in this case the adjustment, in the working operations takes place by means of the pin 0 and eccentric p, of fixed or limited throw.

However, the advantages of the invention could be secured, although in a less favourable manner, by usin the spindle only for adjusting, by fixing tfie adjustment distance 9 by means of a suitable snap ball and socket, a cone stop, a stepped stop, a screw stop or the like, cooperating with the spindle, so that an easy withdrawal to this distance prior to the final grinding can also take place.

What I claim is 1. In a twist drill grinding machine, the combination with a grinding surface and a drill guide casing mounted oblique to the grinding plane, a gage-sto arranged to engage the end of the drill lip opposite to the one being ground and a screw spindle for adjusting said guide casing to and from said grinding surface, a second adjusting member adapted to adjust said guide casing to and from said grinding surface and having a predetermined throw or range of action, so that its reverse action repositions the gage stop to determine on a later grinding of one lip an amount of reduction equal to that produced by a previous grinding of the other lip, thereby bringing the point of the drill accurately into the center.

2. In a twist drill grinding machine, the combination with the grinding surface, and a drill guide casing mounted oblique to the grinding plane, a gage stop arranged to engage the end of the one hp opposite to the one being ground and a screw spindle for adjusting said guide casing to and from said grinding surface,a second adjusting'memher-adapted to adjust said guide casing to and from said grinding surface and having a predetermined throw or range of action, so that its reverse action repositions the gage stop to determine on a later grinding of one lip, an amount of reduction equal to that produced on a previous grinding of the other lip, thereby bringing the point of the drill accurately into the center, said second adjusting member being an eccentric.

3. Ina twist drill grinding machine, the combination with the grinding surface, a drill guide casing mounted oblique to the grinding plane, a gage stop arranged to engage the end of one lip opposite to the one being ground and a screw spindle for adjustingsaid guide casing to and from said grinding surface, a second adjusting member adapted to adjust said guide casing to and from said grinding surface and having a predetermined throw or range of action so that its reverse action repositions the gage stop to determine on a later grinding of one lip an amount of reduction equal tothat produced on a previous grinding of the other lip, thereby bringing the point of the drill accurately into the center, said second adjusting means being an eccentric. and means for setting the throw of said eccentric.

4. In a twist drill grinding machine, the combination with the grindlng surface, a

drill guide casing mounted oblique to the grinding plane, a gage stop arranged to en gage the end of one lip opposite to the one being ground and a screw spindle for adjusting said guide casing to and from said grinding surface, of a second adjusting member adapted to adjust said guide casing to and fromsaid grinding surface and having a predetermined throw of range of action, so that its reverse action reposltions the gage stop to determine on a later grind.- ing' of one lip an amount of reduction equal to that produced on a previous grinding of the other lip, thereby bringing the point of the drill accurately into the center, anIeccentric and means for adjusting the throw of said eccentric, said means consisting of spring detents carried by said eccentric, and cooperating with a member having notches and spring stops cooperating with said notches for setting the,throw of said eccentric. L

In testimony whereof I aflix my signature.

CARL KOBIS.

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