Cutting speed & RPM for Tool steel (O1 / A2 / D2, annealed)
Tool steel (O1 / A2 / D2, annealed) turns at roughly 200–350 SFM with carbide (40–70 SFM with HSS). A 1/2″ tool then wants about 1550–2700 rpm — enter your own diameter below.
Surface-speed bands are starting points · tune to your tool coating, coolant and rigidity
Tool steel (O1 / A2 / D2, annealed) cutting speed — SFM by operation & tool
| Operation | HSS SFM | Carbide SFM |
|---|---|---|
| Turning | 40–70 | 200–350 |
| Milling | 32–56 | 160–280 |
| Drilling | 24–42 | 120–210 |
Turning is the baseline; milling ≈ 0.8×, drilling ≈ 0.6× (rule of thumb). Bands per Machinery’s Handbook and tool-maker charts — starting points, not limits.
These are starting speeds, not targets. Real surface speed depends on tool coating, coolant, setup rigidity and how the chip clears. Start mid-band, then push up while the finish, chip colour and tool wear stay healthy.
Machining Tool steel (O1 / A2 / D2, annealed)
Speeds shown are for the annealed condition. Once hardened, conventional milling gives way to grinding or hard-turning with CBN.
How the RPM is worked out
Surface speed — SFM, or Vc in m/min — is the speed of the cutting edge past the work, and it is the number that actually protects tool life. Spindle rpm is just what that surface speed becomes once you fix the diameter: n = SFM × 12 / (π·D). Halve the diameter and the rpm doubles for the same surface speed, which is why a small drill spins so much faster than a face mill in the same material.
HSS vs. carbide
Carbide holds its edge hot, so it runs roughly three to six times the surface speed of HSS in Tool steel (O1 / A2 / D2, annealed) — the two columns above. HSS still earns its place on flexible setups, interrupted cuts and small-shop drilling, where its toughness beats carbide’s brittleness. Match the speed column to the tool actually in the holder, not the one you wish you were using.
Turning the feed into a number
Once you have the rpm, feed follows from chip load: feed = rpm × feed-per-tooth × flutes for milling. The calculator does this from the values you enter — pick a feed-per-tooth from your cutter’s data, then read the feed rate alongside the rpm.
Need chip-load numbers to set the feed? Tool steel (O1 / A2 / D2, annealed) feed rate & chip load
References
- Machinery’s Handbook — “Cutting Speeds and Feeds”: surface-speed tables by material and tool material.
- Tool-manufacturer speed & feed charts (grade- and coating-specific) — use these to refine the starting bands above.
Last reviewed: 2026-07 · Calculation method & assumptions