Patent GB-110648-A (GB)
Title: Improvements in Machines for Forming the Grooves or Flutes in Twist Drills and the like.
IPC: B23C3/32
Filed: 1916-12-09
Abstract: 110,648. Smith & Coventry and Wright, I. H. Dec. 9, 1916 Milling helical surfaces.-In a machine for milling the flutes in twist drills &c. by moving them relatively to a stationary rotating cutter, the work pieces are carried by a turret having an oblique axis and being automatically rotated, and the work indexed to cut a fresh flute after each reciprocation. The speed of traverse is reduced just before the cutting commences and the cutter is automatically adjusted to vary the depth and width of the flute and is raised to relieve the cutter during the return. The drill D is carried by a chuch 152 having a bayonet connexion to the turret 147 obliquely mounted on the head 142. A spindle 72. having a reciprocating screw motion, has a spring pawl 146 adapted to impart its motion to the head except at the limit of the return movement when the pawl 146 is disengaged by a pivoted spring stop 169, Fig. 6, which also prevents rotation of the head by engaging a pin 171. One of a number of pins 148. Fig. 1, carried by the spindle 72 engages one of the pins 173 on the turret 147 which is thereby turned to bring the next blank into position. When this movement is complete, the pawl 146 engages the next recess in the head and the motion is reversed for the next cut. The number of flutes is even and the number of blanks is odd. or vice versa. so that all the flutes of each drill will be automatically cut. The spindle 72 engages a fixed nut 20 and carries a gear 44 engaging a long gear 35 which is driven by a gear 43 on a shaft 70 having a clutch 47 adapted to engage one of two bevels 45, 46 and a clutch 51 engaging the worm wheel 30 through a oneway ratchet 52. The bevel 45 is driven through bevel 50 by the bevel 46 which is driven from the step pulley 5 through the shaft 69 and spur gear. The worm wheel 30 is driven from the bevel 50 through gears 48 and a worm. The clutches 47, 51 are operated by a bar 80 which. in its left-hand position, clutches both wheels 30 and 45 to the shaft 70, but as the ratchet 52 is over-run, the drive takes place through the bevel 45, a rapid advance of the blank towards the cutter being effected. A slight movement of the bar to the right unclutches the wheel 45 only and the ratchet 52 drives for the slow cutting stroke. A further movement of the bar 80 releases the wheel 30 and clutches the bevel 46. giving a rapid return of the blank. The bar 80 may be moved into such a position that all the clutches are disengaged by a hand-operated pin 85. The bar 80 is given its slight movement by a disk. adjustable on the spindle 72, engaging a lever 99 in contact with a pin 82 on the bar. The movement is completed by an adjustable stop 98 which engages below a projection on a bar 19 as this travels along a helical groove in a cylinder connected to the gear 35. The bar 19 is connected tc a lever 15 also connected to the bar 80. Complete movement of the bar is ensured by a spring- pressed lever 16 having inclined faces engaging corresponding faces on the lever 15. The cutter C is carried by a frame 4 adapted to turn and move axially on a vertical pin 122, Fig. 3. The frame 4 is moved vertically by a cam 131 having an arm 12 to which an adjustable block can be clamped. This block is connected by a link 105 to a nut 31 on a screw spindle which is secured to the rotary spindle 70. The frame 4 can also be connected by a link to the nut 31 so that it is turned to vary the width of the flute cut in the blank D which is supportad by a fixed guide 28 The cutter is adjusted vertically by means of a hand-wheel 80<x> which rotates a screwed sleeve 125 in a fixed nut 124 by worm gear 29. The cutter is raised to relieve it during the return by a lever 14 and cam 104. The cam is carried by a sleeve 40, Fig. 1, which is rotated by a friction clutch 68 unless held by one of two pins engaging corresponding pins on a lever 17. Thislever is moved by the bar SO so that, at each reversal of the movement of the blank, the cam 104 makes a semi-revolution.