I would like to hob a gear on my cnc mill using the 4th axis and need some help.Its an xyz 1020 vmc running Siemens 828 controls.It works with both Sinumeric or Fanuc style g code programming.I have a 0,3 module gear hob.Please note this is a hob, not an involute cutter , and so it needs to run at a set speed in relation to the 4th axis.The cutter needs to turn 100 times faster than the 4th axis to cut a 100 tooth gear.This bit i can do. If i program S495 and a feed of 1800°/minute for the A axis. That relates to the 4th axis turning at 5rpm.All fine and well, and that will give me the 99 teeth on the gear that i need.

Now, how can i program a different feed rate in mm/min to contol the actual motion of the x and y axes to work in conjunction with the A axis?Surely there must be a way of doing it, either with f groups or possibly with a feed inversely proportionate to time? One of the G codes in the 90's does this. Any advice would be most welcome !