Patent GB-257808-A (GB)
Title: Improvements in and relating to the manufacture of twist drills
IPC: B23C3/32
Filed: 1926-01-12
Abstract: 257,808. Whitehouse, A. E. Jan. 12, 1926. Drills.-In a process for making twist drills, a rod of material is advanced axially and simultaneously rotated by means of obliquelyarranged feed-rolls which move the rod past a pair of inclined milling-cutters which simultaneously cut both flutes. At the end of the feed movement the drill is pointed and cut off. On the bed 11 are mounted a main shaft 12 driven by pulleys 14 and driving through spiral gears 15 a shaft 16 which through worm gearing drives a shaft 13. The shaft 16 is also connected through chain gearing 19, shaft 20, and worm gearing 21 to a cross-shaft 23. The bed 11 carries a longitudinal slide 25 having pivots 29 for two parallel pairs of plates 27, 28 the outer ends of the plates being guided in slots in the frame so that longitudinal movement of the slide 25 causes equal simultaneous angular adjustment of all the plates. Each plate carries a longitudinally-adjustable bearing having a lug 39 coacting with graduated adjusting screws 40. Revolvable sleeves 41 - - 44 are mounted in the bearings and are eccentrically bored to receive shafts 45 - - 48, the eccentric adjustment of the sleeves 41, 42 being effected by means of arms 49 coacting with graduated set-screws 50. The shafts 45, 46 carry milling-cutters 55 which are shaped so as to cut the groove and relieve the cutting edges simultaneously. Movement of the cutters towards the work is limited by the setscrews 50. The shafts 47, 48 carry feed rolls 56 which are always parallel to the cutters and which impart the required rotary and longitudinal movement to the work. The cutters are driven in opposite directions from skew gears 58 on the shaft 12 through spur gears 59, 57. The feed rolls are similarly driven from the shaft 13. In order to regulate the stock feed, the shaft 16 may swing about the bearing 17 to disengage the drive of the shaft 13 when required without affecting the engagement of the spiral gears 15. Pointing of the drill is effected by an end-milling cutter 75 which is chain driven from the shaft 20. The pointing cutter is normally held inoperative by a spring 79, but is brought forward at the required moment for the pointing operation by means of a cam 83 on the shaft 23, the cam being provided with a dwell to maintain, the engagement of the pointing-tool with the blank during the severing operation. The pointing-tool is equipped with a drill-with-drawing device comprising spring arms 108, Fig. 12, which are withdrawn by a stationary ring 110 when the pointer is retracted. The severing saw 86 is mounted in a hinged frame 88 and is driven from the shaft 20 by gearing 93, 92, 91. Rocking of the saw frame is effected by a cam 98 on the shaft 23 which acts through a rocking lever 94. The stock is fed through guides 104, 105, mounted on the slide 25 the guides being provided with interchangeable bushes to accommodate different sizes of stock. In operation, the cutters preferably work in the track of the feed rolls so that any marks made by the latter are erased. After the required flute length has been cut the feed roll driving-gear is disengaged by a cam 68 and rocking lever 65 whereupon first the pointing-cutter and then the severing saw are brought into operation. At the same time the cutter sleeves are actuated through cams 72 and rods 51 so that the cutters are withdrawn clear of the work. The feed device is then re-engaged and the stock is again moved forward and the cutters are returned to cut another drill while the severed blank is ejected, by the advance of the stock and drops into a receptacle. In a modification, Fig. 11, the cutter shafts 45. 46 and the feed roll shafts 47, 48 may be arranged as shown and driven by bevel gears 570. The sleeves 410, 420 may also be geared together and provided with a single micrometer adjustment. For making large drills the cam 72 may be arranged so as to cut flutes which are deeper at the point than at the shank end,