GB653254A - Improvements in or relating to apparatus for grinding screw threads - Google Patents

Abstract

653,254. Forming screw threads by grinding. LANDIS TOOL CO. Sept. 17, 1947. No. 25365. Convention date, Feb. 21, 1946. [Class 60] A grinding wheel 12, Fig 4, has a roughgrinding section B, with a number of circumferential ridges 33 of successively increasing external diameter for progressively rough forming a screw thread on a workpiece 24 and, adjacent the larger diameter end of the section B, a finishing section C with a number of circumferential ridges 38 of substantially the same diameter and conforming substantially to the shape of the grooves of a finished screw thread. The section B may be pre, ceded by a plain section A which has a bevelled edge 32 and may be provided with a taper over the whole or part of its length. The ridges of section B may increase in both diameter and depth and decrease in crest width towards section C as shown in Fig. 4 or they may progressively increase in diameter and be of uniform depth as shown in Fig. 5. The grinding wheel forms part of a centreless grinding machine in which the control wheel may be cylindrical, concave or of the form shown in Fig. 4 in which a cylindrical section 47 ranges with a section 48 increasing in diameter towards the throat exit and provided with a succession of ridges 50 to provide greater surface contact with the work. The control wheel is mounted on a base angularly adjustable in a horizontal plane and slidably adjustable towards and from operative position. A base 21. Fig. 9, carries a vertically adjustable work rest 22 and supporting members 27 for guide plates 26 which are adjustable towards and away from each other to suit the diameter of the workpiece. One of the supporting members carries a dressing device 28, Fig. 7, for dressing the control wheel 15. A guard member 30 positioned so that it does not normally make contact with the workpieces prevents the latter from being ejected out of the throat. The grinding wheel of Fig. 4 may be formed by first using a crushing roller with a series of uniform V-shaped ridges and then truncating the ridges so formed with a diamond traversed at an angle to the wheel axis. The inclined traverse may be obtained either by mounting the diamond on the control wheel base or by mounting it on the grinding wheel fender to cooperate with a template. An alternative method of forming the wheel comprises using the diamond first to give the wheel its general shape and then producing the ridges with a contoured crushing roller. The grinding wheel of Fig. 5 may be formed by the latter method. Specifications 601,030 and 617,329 are referred to.