How-To: Feed Rate Calculation

[Jonathan]

Depends on your definition of free.

The one I use the most is:

http://www.cnccookbook.com/CCGWizardv40.html

(Unless you count doing some quick mental arithmetic and guessing!)

His is good because it calculates tool deflection, so you can get a rough idea of the surface finish and how close the tool is to breaking. I also use that when trying new materials by adjusting the depth of cut until the tool deflection is at the value I know is safe for that cutter in a known material. For instance I know on my machine that with a 6mm single flute cutter it will run all day with 1.6um tool deflection in aluminium but if I exceed that the surface finish is worse. So a few days ago I tried cutting mild steel with the same cutter on the router. Adjusted the depth of cut to get a calculated 1.6um deflection then did a test cut at that feedrate and depth of cut. It worked well...much less messing about to find the optimum.