I have a Taig mill and a Taig fly cutter. I have a speeds & feeds chart for endmills in various materials, but don't know what S&F to use w/ my fly cutter in different materials. Is there a chart or standard calculation for this? Is there any general advice from some folks using the Taig mill and fly cutter? I'd seen a formula (from Sherline) for calculating the RPM for cutting steel:

3.8 x cutting speed (ft/min) / cutter diameter (in)

but given that my mill (cnc) moves at a rate of inches per minute, my mill couldn't produce speeds low enough. Additionally, it doesn't seem to take depth of cut into account.

Advice would be very much appreciated!