Posted by rob on April 24, 2017 at 18:01:20:
In Reply to: Fellows 20-4 cutter offset posted by Ben on February 17, 2017 at 17:40:46:
the formula I use is to first find the center distance of the internal (cd) using this formula. (gear pd-cutter pd)/2
then you find cutter offset=cd×sine back off angle. normally I use sine 5 degrees which is .08715. if trimming still happens add additional .02 to offset. I've only used offset for one job which was a standard internal of 53 teeth 3 mod pitch and 20 degrees pressure angle. offset to the left .140. the formula was givin to me by a 20-4 fellows mechanic