GB518688A - Improvements in or relating to a boring tool, particularly for boring taper holes - Google Patents

Abstract

518,688. Drills. STEVENS, A. H., (Shawlock, Inc.)..Sept. 2, 1938, No. 25726. [Class 83 (iii)] In a tool for.drilling tapered holes the cutter is loosely supported within a bore in the shank having flat side walls for guiding the cutter and against which it pivots in one direction, an inclined stem on the cutter being engaged by a sleeve slidable in the shank and normally urged forwards by a spring. The tool comprises a hollow body 10 attached by a pin 14 to shank 42 and haying a square-section axial hole 12 to receive the stem 21 of the bit 15. The stem is loosely supported in the hole by a pin 22 and has two opposing flat sides which are a close fit against the sides of the hole and sides at right angles thereto which permit the stem to rock. The inclined portion of the stem passes through a block 38 slidable in a slot 39 in the body 10 and attached to a sleeve 24 surrounding the body. A spring 25 presses the sleeve against a thrust washer 27 and another sleeve 26 which carries a work-engaging member 28 provided with apertures 30 and spurs 31 to penetrate the work. An outer sleeve 32 pinned to the shank at 34 has a lower flange 35 co-operating with a felt washer 36 on the sleeve 26 to limit the downward motion of the latter and provide lubrication. In operation, the spring 25 maintains the sleeve 24 &c. in the lower position and the bit abuts either against the shank 42 or against the lower end of the body 10, and the tool is rotated and fed downwards to cut a parallel hole in the work. When the member 28 meets the surface of the work, further motion of the sleeve 24 and block 38 is prevented and,the stem 21 slides through the block to rock the bit and cause the base of the hole to be counterbored as shown, three sides of the stem always remaining in contact with the interior surfaces of the body to give it adequate support. In a modified form of bit a twisted body 112, Fig. 14 has a centre point 116, side points 118 and radial cutting-edges 115 which are swept forwardly and relieved on the end faces. One edge 118 of the bit is relieved to allow it to cut laterally whilst the other is cylindrical to guide the bit in forming the preliminary cylindricalhole. The upper end of the hole may be countersunk by means of a second cutter 148 and the bit is then arranged to project further from the body.