GB595593A - Improvements in or relating to the lapping of screw threads - Google Patents

Abstract

595,593. Grinding. STEVENS, A. H. (Sheffield Corporation). Sept. 20, 1943, No. 15403. [Class 60] The thread on a tapered gauge &c. is lapped by means of a tapered threaded lap, the workpiece and the lap being rotated and the lap fed axially. As applied to the lapping of a tapered thread ring gauge, the gauge 26, Fig. 2, is carried in a work-holder 11 mounted on a base 10, which carries also a tool support 12 and a drive shaft bearing 13 ; the support 12 carries a tool formed as a tapered threaded plug 48. The work-holder and tool are driven in opposite directions by belt &c. gearing from a motor. The work is held on an arbor 27, mounted in bearings 29 in the holder 11, by clamps 28 and is centred by a tapered plug which has a cylindrical portion fitting a chamber 34 in a piston 33 slidable by a stem 35 in the arbor 27 ; when the centred work is clamped, the plug 37 is withdrawn. The pulley 24 is secured to a hollow shaft 40 rotatable in the bearing 13, the shaft 40 having therein slots 41 to act as guideways for rollers 42 on a pin secured to a rod 44, which is connected by a flexible coupling 45 to a shaft 46 fixed in the tool holder spindle 49. The support 12 is mounted to slide to and from the work on a carrier 52, balls or rollers 55 being provided between the parts, the carrier 52 being angularly adjustable on, and secured by screws 60 to a plate 56 secured to a plate 57 guided to move transversely of the work by a base 58, balls or rollers 59 being interposed between the parts 57, 58 ; the carrier 52 is set to align the movement thereon of the support 12 with the taper angle of the threads in the work, and the overhanging end of the carrier is supported by a foot 82 screwed into the plate and resting on a smooth flat surface on the base 10. The lapping tool 48, which may be made of cast iron &c., is longer than the thread to be worked. and is pressed against the work by a spring 63, Fig. 10, located in the plate 57 and adjustable by a stop 64 screwed in a lug 65 on the base 10 ; the extent to which the tool can move laterally is fixed by an adjustable stop 69 with which the side surface 68 of the plate 57 is adapted to contact. In operation, the work and the tool are rotated, the tool is moved into the work by manipulation of a handle 62 on the support 12 and, with the threads on the work and tool in engagement, the tool is moved through the work by such engagement ; the direction of rotation of the work and tool then is reversed, the tool moving back to its starting position, this being repeated until the surface 68 engages the stop 69. Reversal is effected automatically by means of switch gear at the ends of the strokes.