GB410603A - Method of forming a splined member by hobbing - Google Patents

Abstract

410,603. Hobbing splines. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Barber- Colman Co.; River Street, Rockford, Illinois, U.S.A.) April 21, 1933, No. 11732. [Class 83 (iii).] In a method of hobbing a splined member 10 a hob 15 is located with its axis inclined to a perpendicular to the work axis 10<1> in accordance with the inclination of the hob thread and is fed transversely across the work while the hob and work are continuously rotated in timed relation. The sides of each key 12 on the work are parallel so that the sides of a groove 13 converge inwardly, the roots a of the groove being tapered longitudinally. Preferably clearance grooves 14 are formed at the longitudinal margins of the roots a. The hob has a cylindrical body with one or more threads 18 intersected by longitudinal gashes perpendicular to the threads to form teeth having relieved tops C, each thread being tapered from end to end of the body. The tops of the teeth are axially inclined in accordance with the taper. Lugs 21 may be provided to cut the clearance grooves 14 but if these are not required, the lugs may be dispensed with. The profile of the hob threads depends on the form to be generated. In operation, the hob is positioned as shown in Fig. 6, with the large end adjacent the work, the inclination being such as to bring the hob threads at the point of operation parallel to the work axis. The hob and work are rotated in timed relation and the hob is fed diagonally across the work in the direction n so that the large end of the hob cuts grooves of maximum depth at the point g while the small end subsequently engages the work at the point g<1>. The component h of the hob movement is preferably constant while the component i is varied according to the required length of the work grooves, being such that the intercept on a line parallel to the work axis made by lines passing through the ends of the hob and drawn in the direction of the feed, is equal to the required groove length f. Fig. 6, shows a triple-threaded hob, but in some cases a single thread hob may be used. In a modification, Fig. 7, the hob may be arranged so that when it is in correct angular relation to the work piece its projected length f on the work axis is equal to the groove length required. In this case the hob is fed perpendicularly to the work axis between the positions shown. Specification 410,604 is referred to.