Workpiece material / Cast iron
Gray Cast Iron speeds and feeds
Starting surface speeds and chip loads for milling Gray Cast Iron. Every value below is cross-checked against published sources and linked, so you can re-verify it yourself. Starting points, not limits.
- Hardness
- 200 HB
| Value | Used | Provider readings (each linked) |
|---|---|---|
| Surface speed, HSS (estimated) | 70 SFM | |
| Surface speed, carbide (estimated) | 300 SFM | |
| Chip load @ 0.25" (estimated) | 0.0016 in/tooth |
| 0.125" | 0.25" | 0.5" |
|---|---|---|
| 0.0008 | 0.0016 | 0.0032 |
| Constant | Value | Readings |
|---|---|---|
| Kc1.1 (specific cutting force) | 1,050 N/mm2 | ISO group-typical - see notes |
| mc (chip-thickness exponent) | 0.27 | ISO group-typical - see notes |
| Unit power | 0.60 HP/(in3/min) | ISO group-typical - see notes |
The power-model constants (Kc1.1, mc, unit power) are class-typical values for the ISO material group, used only for a rough spindle-power estimate. Only their relative ordering and internal consistency are verified, never tuned to match any vendor.
Notes
Gray cast iron machines dry and produces a powdery chip; carbide is preferred. Starting values are for general milling of class 30 gray iron around 200 HB. Power-model constants: Kc1.1 and mc are class-typical values; unit HP is derived from Kc, not independently published.
Verify this yourself
Every number above links to the provider that publishes it. Open two or more and confirm they agree with what is shown here. Full source list:
Take these into the feeds and speeds calculator for RPM, feed and power. Start a little under these numbers on a light or flexible setup.