Patent GB-654001-A (GB)
Title: Improvements in or relating to machines for fluting drills, reamers, taps, and the like
IPC: B23C3/32
Filed: 1948-09-11
Abstract: 654,001. Grinding flutes in drills, reamers, taps &c. STORER, G. E., and LIDSTER, H. Sept. 11, 1948, No. 23906. [Class 60] [Also in Group XXII] A machine for forming flutes in drills, reamers, taps and the like of the type in which a drill or like blank is mounted in a holder in non-rotatable connection with one gear meshing with a driving gear, the driving gear rotating with a barrel cam serving to move the holder lengthwise with a stroke first in one direction to carry the blank past a flute - forming tool and then with an idle return stroke in the other direction, at the end of which the blank has been rotated to a new angular position corresponding to the separation of two of the flutes to be formed, comprises a work-holding carrier pivoted with respect to the forming tool and having an edge cam rotating with the barrel cam and the driving gear to vary the inclination of the carrier and thereby to withdraw the blank from the tool in the return stroke. The machine comprises a bed 1 having a raised portion 2 carrying a grinding spindle 3 driven by V-pulleys 10 and belts 11 from a motor 12; the portion 2 is skew to the remainder of the bed 1 so as to bring the plane of a form-grinding, wheel 13 out of line, by the approximate value of the helix angle of the flutes to be formed, with the centre line of a workholding carrier 4 carried on a table 6. The table 6 is carried by a knee 15 in slideways 16 on a box 17 fitted slightly canted in the lower end 5 of the bed 1; the knee 15 and table 6 are vertically adjustable by worm gearing 20, 21 operated by a handwheel 19. The tilting of the table 6 corresponding to the canting of the box 17 enables cutting oil or other compound to drain into a sump within the bed 1 for recirculation. The upper part of the carrier 4 comprises slideways 7 for a reciprocating work-carrying head 8; the carrier is mounted by a transverse pivot 9 on a swivel plate 29 pivotal at 32 to the table 6 and secured by a screw 30 passing through a clearance slot 31; by means of a scale 33 the axis of the work head 8 can be adjusted with respect to the plane of the grinding wheel 13 in accordance with the precise helix angle required. A motor 23 on the knee 15 drives, through reduction box 25, V-pulleys 24, 27 and belt 26, a transverse shaft 28 in the carrier; the shaft 28 drives, through worm gearing 36, 35, a longitudinal shaft 34 carrying a barrel cam 37 and an edge cam 38, the latter being kept by the weight of the carrier 4 in contact with a follower roller 39 carried by a fixed pillar 40 on the plate 29. The cam 37 has a groove 43 engaged by a tapered follower 41 protruding downwardly from the carriage 42 of the work head 8, whereby rotation of the cam reciprocates the work head. A shaft 44 in the head 8 carries a gear 45, somewhat longer than the flutes to be ground, meshing with a spur gear 46 on the shaft 34. The blank is held by a chuck 47 and the part to be fluted projects through a bush 48 in a holder 49, an inclined slot 50 passing through both parts 48, 49 to receive the grinding wheel. The groove 43 in the barrel cam 37 is shaped from a-b to give a quick traverse motion to bring the point of the blank into the bush 48 from b-c to give a slower traverse motion during which the flute is ground, from c-d to give a quick return, and from d-a to give no axial movement of the blank. During the grinding stroke the edge cam 38 may vary the inclination of the carrier 4 so as to effect slight tapering of the depth of the flute; during the return stroke the edge cam 38 allows the carrier 4 to drop about the pivot 9. For cutting blanks with two flutes the gears 46, 45 have a ratio of 3¢:1 so that when the blank has been advanced and retracted once it has made 3¢ revolutions and is therefore indexed by 180 degrees with respect to its starting position; a ratio of 4¢:1 may be used. For forming three or more flutes, ratios will be chosen to give 120 degrees indexing. If the gears 45, 46 have straight teeth the helix angle of the flutes is a function of the combined rate of advance and rate of rotation of the blank; the gears 45, 46 may have helical teeth in which case the rate of advance derived from the cam 37 may be increased or decreased accordingly as the hand of the teeth on the gears 45, 46 is in the same direction as or opposite to the hand of the rotation of the blank resulting solely from the drive imparted through the gears 45, 46. Thus, the rate of advance may be slowed down to occupy a larger part of the complete rotation of the cam 37, the non-cutting return stroke being correspondingly speeded up. The cutting angle may be modified by appropriate formation of the groove 43 of the cam 37 over its advance section b-c, even to the extent of being parallel to the axis of the blank if the rotation of the blank due to the combined action of the cam 37 and the rotation imparted by the gears 45, 46 is cancelled out by a reverse rotation imparted by the helical teeth of the gear 45 moving along the helical teeth of the gear 46, the whole of the indexing movement taking place in the return stroke c-d. The machine may thus be used for grinding straight-fluted reamers. taps and the like, the angle of the tool in relation to the blank being correspondingly adjusted. When the whole of the flutes have been cut the work is brought automatically to rest by a trip mechanism. A pinion 51 on the shaft 34 meshes with a pinion 52 of twice the diameter so that at every two revolutions of the shaft 34 a notch 53 in a sleeve 54 on the pinion 52 allows a plunger 55 to enter; this takes place when the cam follower 41 is between d and a. The plunger 55 is pivoted at 56 to a lever 57 pivoted at 58 at one end and urged at the other by a spring plunger 59. The lever 57 is formed as a yoke 60 to surround the shaft 28 and in the arms of the yoke loose pivot-pins 61 carry pads 62 fitting a groove 63 in a slidable dog clutch part 64 facing a corresponding part 65 secured to the shaft 28. Passage of the plunger 55 into the notch 53 thus enables the spring plunger 59 to disengage the dog clutch, and driving of the shaft 34 not only ceases but the shaft is prevented from turning by the plunger 55. To start or restart the machine the plunger 55 is withdrawn and the dog clutch re-engaged by a handle 66 on a spindle 67, a lever 68 on the latter having a fork engaging a projecting end 70 of one of the pins 61. In a modification, Fig. 11, the work head shaft 44 has a gear 71 meshing with two gears 72 each carrying a chuck 73 so that two blanks may be simultaneously presented to two grinding wheels 74.