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Milling 304 stainless: speeds, feeds and flutes
Conservative starting values for 304 stainless and how to avoid work hardening.
Harvey Tool lists 100-250 SFM for carbide in austenitic stainless (304, 316, 321) [1]. 6GTools lists 180-250 SFM depending on the tool series [2]. HSS runs 40-70 SFM per Travers [3]. ChiploadPro starts carbide at 200 SFM and HSS at 45.
| Diameter | Harvey IPT [1] | 6GTools IPT [2] | ChiploadPro start |
|---|---|---|---|
| 1/8" | .0001 | .0004 | .0003 |
| 1/4" | .0005 | .0009-.0013 | .0008 |
| 1/2" | .0015 | .0019 | .0016 |
| 3/4" | .003 | .0026 | .0025 |
Flute count
Harvey recommends 4 flutes for slotting stainless (bigger flute valleys clear chips), 4 or 5 for traditional roughing, 5 or more with a helix over 40° for finishing, and 5-7 for high-efficiency milling [4].
Work hardening
304 work-hardens. Keep the tool cutting, not rubbing. Digital Machine's chart notes that too light a chip work-hardens the surface [5]. If you slow the feed to "be safe," you can make it worse.
Tooling for this job
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