Drill RPM converts a target cutting speed (SFM) and drill diameter into the spindle speed that keeps the drill’s outer edge cutting at the rate the tool and material can handle.
How it works
Cutting speed describes how fast the cutting edge moves through material, independent of tool size, so a larger drill needs a lower RPM to hold the same SFM as a smaller one. Once RPM is set, the drill’s feed rate is calculated separately from the recommended feed per revolution for that diameter and material.
FAQ
What SFM should I use for drilling? It depends on drill material and workpiece: HSS drills typically run 80 to 120 SFM in mild steel, 250 to 350 SFM in aluminum, and 40 to 60 SFM in stainless or tool steel. Carbide drills can run roughly 2 to 3 times higher than HSS in the same material.
Related Guides
CNC Calculators · Drill Feed Calculator · Feed per Revolution Calculator