Posted by Dan McEachern on May 07, 2002 at 18:45:20:
In Reply to: accuracy of ratio posted by steve green on May 05, 2002 at 23:59:12:
Steve- as a general rule, when hobbing spur gears, the index ratio must be exact- or you will experience some helix generation upon cutting. Since most hobbing machine index ratios are a whole number divided by the # of teeth, it is a simple task to find exact ratios for index trains.
An exception may be for large prime #'s of teeth.