GB592888A - Improvements in or relating to reamers, broaches or similar cutting tools - Google Patents

Abstract

592,888. Reamers, broaches, &c. FEAR, R. G. Oct. 4, 1944, No. 19029. Convention date, Sept. 13, 1943. [Class 83 (iii)] A reamer, broach or similar tool has a helical cutting edge 12, Fig. 1, projecting from the body and making an angle of not more than twenty degrees with a plane normal to the tool axis. In one form the body 11 has the cutting edge formed by a double threaded helical land 14 which has a taper of about 0.02 inch per inch of length over the leading portion 19 and is parallel over the portion 20. The double thread of the land 14 enables the diameter of the reamer to be measured readily by diametrically opposed contacts and it may be formed by a turning operation. On the leading third or half of the reamer the land 14 has cutting rake of about 8 degrees and the circumference has radial clearance whilst the remainder is ground cylindrical to have a burnishing action. In another form the reamer is formed as a shell 23, Fig. 3, having tapered portions 25, 26 in the bore engaging a conical mandrel 42, the cutting land on the entering portion 35 being conical and on the rear portion 36 cylindrical. The shell is driven by lugs 39 on the mandrel entering slots 38 therein. In another form, which is expansible, the shell 65, Fig. 4, has axial slots 46 extending from the rear for about three quarters of the length and is expanded by a sleeve 61 screwing in the shell at 56 and having a conical portion 62 engaging the conical rear end of the shell. In another expansible form the shell 68, Fig. 6, has axial slots 96 and a rear tapered portion 81 of the bore co-acting with a conical portion 82 of the mandrel 87. To increase the diameter of the reamer by a specified amount a collar 67 is screwed rearwardly on the mandrel to allow the required expansion as indicated by graduations 93 on the mandrel and an index 95 on the collar, and the shell is then forced rearwardly on the mandrel by a screw 86 until the conical exterior 90 of the shell engages the similar interior of the collar 67. In each form the cutting land may be single or multiple threaded and the cutting rake of the entering portion may be ground rearwardly progressively as the tool becomes worn,