G-Wizard Machinist’s Calculator A Quick Feeds and Speeds Course
All Machinists Know the Basics RPM = SFM * 4 / Cutter Diameter Feed Rate = RPM * Chip Load * Teeth Isn’t That Good Enough???
4 Problems Tables Are Worst Case Estimates Chip Thinning Compensating for Odd Shapes Tool Rigidity Classic Formulas Don’t Consider All the Variables…
#1 Tables are Worst Case Estimates Only a Few Variables: Full Range of Tool Diameter, Depth of Cut, Width of Cut, Materials, etc. No Interpolation No Idea of Coolant or Other Conditions What About Micro-Milling? Is Manufacturer Pushing Tool Life or MRR? Have to Assume Worst Case HSM Toolpaths can go 3-5x Faster
#2 Chip Thinning Chip Thinning: Simple formulas assume the red chip The blue chip is reality. You have to feed faster to get to the recommended chipload!
Irony: Babying the Cut is Bad For Cutter Life! Think of the Cutter Edge Radius Versus the Chip Thickness: Radius <= Chip Thickness: Shearing Cut Radius > Chip Thickness: Rubbing!