A method of NC gear cutting with a simply shaped tool. (2nd Report, Worm wheel cutting with a fly tool).

Abstract

The so-called fly tool method of cutting hourglass shaped worm wheels offers an economical production of large-size worm gears. This method however, gives us only an approximate tooth surface of the wheel. The previous reports introduced the numerical control (NC) technique to the fly tool method for making a tool which is able to trace the wheel surface. The fly tool method demands high responsibility of the NC servo to obtain a high cutting speed. To prevent the speed problem, this report discusses two methods of end milling : (1) the end mill tool is driven as the tool of the fly tool method, and (2) the tool is fed in the orthogonal three directions. The tooth profile errors of wheels cut with these two methods are investigated. Compared to the latter method, the first method gives a higher precision of profile, but it is difficult to realize the motion of the tool. A bronze wheel is cut for a trial with the latter method, and the tooth bearing pattern is checked. A method of tooth surface modification is proposed.