GB553502A - Improvements in or relating to precision boring and drilling - Google Patents

Abstract

553,502. Drilling-jigs. BUSH, H. D., and LEWIS, J. J. Nov. 20, 1941, No. 14906. [Classes 83 (ii), 83 (iii) and 83 (iv)] Assembling force-fits.-Holes such as those usually made in a precision jig-boring machine are made in an ordinary drilling machine and subsequently reamed. The error in location of the hole is then measured and two eccentric bushes are adjusted with relation to one another and to the work and then pressed into place so that the hole in the inner bush is in the exact location required. The external diameter of the bush B. Fig. 2, is equal to that drilled in the jig and the eccentricity of its bore and that of the bush C are preferably equal and of the order of one hundredth of an inch. The extensions may be serrated to fix them in position after assembly or an inclined hole may be provided in the inner bush and the outer bush and work A drilled through this after adjustment to receive a locking pin D, Fig. 4. The ends of the bushes have reference grooves B2, C2 or other markings such as graduations to facilitate adjustment. The bushes may be adjusted relatively to one another by members, E, F each being clamped to one of the bushes by a screw E2, F<SP>2</SP> holding the bush against a V-seating with sliding rods E<SP>1</SP>, F<SP>1</SP> engaging the grooves B<SP>2</SP>, C2. One bush is first entered into the other and the adjustment is effected by pointers E3, F<SP>3</SP>. A modified device employing oppositely sliding V-members operated by a right and left hand screw. A device for inserting the bushes in the jig comprises a frame L bushed at L<SP>2</SP>, the bush being splined to a spindle M having a spring pressed head N, with ribs, to engage the grooves in the outer bush, and a pilot M2. A bush having the diameter of the hole in the jig is first placed on the pilot and the frame L is set in correct relation to the jig, assisted by pointer L4, and clamped. The compound eccentric bush is then placed on the pilot and turned to the predetermined position by means of a pointer L<SP>3</SP> on the bush L<SP>2</SP> and scale O. The bush is then pressed into position by the spindle M.