Patent GB-513677-A (GB)
Title: Method of finishing surfaces and machine therefor
IPC: B23C3/02
Filed: 1938-01-18
Abstract: 513,677. Milling - machines. NATIONAL BROACH & MACHINE CO. Jan. 18, 1938. No. 1654. Convention date, Feb. 8, 1937. [Class 83 (iii)] Cutters.-In a method of finishing surfaces such as a cylindrical surface 21 and an adjacent annular face 23 at the back of a bevel gear 22 integral with a motor car axle 20, Fig. 7, a tool or tools having bevelled surfaces interrupted by grooves to form lands provided with cutting edges are positioned with a bevelled surface in line contact with each surface to be finished, the tool and work being simultaneously rotated and pressure contact maintained between tools and work. In a machine, Fig. 1, for finishing the surfaces 21, 23, the work is supported between a motor driven stock 12, adjustable from a handle wheel 18 and a centre 19 while the tools are driven as shown from motors 26 through suitable reduction gearing. A fourth motor drives through worm gearing 31 a cam 29 controlling the tool feeds. The tools are carried on slides 13, 14. movable at right angles to the respective tool axes and the slides are fed to take a definite cut in the work by means of toggle mechanism comprising links 32, 34, the latter being secured to shafts 36 interconnected by arms 37 and link 38. The latter is operated by a pivoted lever 41 from the cam 29 which has a low portion into which the roller may drop to break the toggles and withdraw the tools from the work. Limit switches may be provided to stop the motors, for loading and unloading. The cutter 24 is of bevelled form and its spiral teeth, Fig. 6 have a clearance a of about 2 degrees and front rake # of about 5 degrees. The pitch in normal section is 0.16 inches and the tooth depth 3/32 inch. The tops 51 are 3/64 inch wide, the diameter 6 11/16 inches and the face width 1 inch. The tool 25 is similar but the spiral teeth are of opposite hand, the relative rotation. of tools and work being such that the work surface moves against the shaving edges of the tool. The speeds of the work and of the tools 24, 25 are respectively 425, 125 and 250 R.P.M. The finishing cuts are about .012 inch on the cylindrical part and .020 inch on the annular part of the work. In a modification the tools may have additional oscillatory movements of about 1/8 inch as shown by the arrows 20 and 60, Fig. 7, either during or at the end of the in feeds perpendicular to the tool axes. Instead of the work and tool axes being coplanar as in Fig. 1 they may be in different planes as in Fig. 11, the tool face being of slightly dished form 72 so as to obtain a wide zone of contact 70, 71 between tool and work. A feed along the work axis may also be given. In another modification, the cutter may be oftaper worm form. Fig. 12 with equal lands and gashes about .06 inch wide, Concave grooves 78 may be provided in the lands. to reduce the contact surfaces. The lands act as limiting gauges and by suitably adjusting the pressure between tool and work very light cuts may be taken. In another modification, Figs. 13 and 14, the tool may be fed in along either of the arrows 86 or 87 and in addition there may be a cross feed in direction 88, 89. In some cases a,feed longitudinally (f the work may be imparted. In another modification, Fig. 15 the cutter may be shaped so as to form a radiused corner 90 adjacent the cylindrical part 91 of the work. In another modification the tool may have straight instead of spiral cutting edges. The Specification as open to inspection under Sect. 91 describes also a modification in which a wide cylindrical cutter is disposed on an axis inclined to the work axis and is reciprocated transversely to the cutter axis to spread the shaving action over the work surface. This subject matter does not appear in the;Specification as accepted.