Reference data
CNC cutting data by material
The starting surface speeds and chip loads behind the feeds and speeds calculator. Each figure is a conservative published starting point, drawn principally from free tool-maker charts such as Harvey Tool and Lakeshore Carbide. They are starting values, not limits.
| Material | Group | SFM (HSS) | SFM (carbide) | Chip load @ 1/4" (in/tooth) | Hardness (HB) |
|---|---|---|---|---|---|
| Aluminum 2024 | Aluminum | 250 | 750 | 0.0020 | 120 |
| Aluminum 6061 | Aluminum | 250 | 800 | 0.0020 | 95 |
| Aluminum 7075 | Aluminum | 250 | 750 | 0.0019 | 150 |
| Alloy Steel 4140 | Steel | 70 | 300 | 0.0013 | 200 |
| Alloy Steel 4340 | Steel | 60 | 280 | 0.0013 | 220 |
| Mild Steel 1018 | Steel | 90 | 350 | 0.0015 | 126 |
| Steel 12L14 (free-machining) | Steel | 110 | 400 | 0.0016 | 160 |
| Stainless Steel 303 (free-machining) | Stainless | 60 | 250 | 0.0013 | 160 |
| Stainless Steel 304 | Stainless | 50 | 200 | 0.0012 | 170 |
| Titanium Ti-6Al-4V | Titanium | 35 | 150 | 0.0010 | 330 |
| Gray Cast Iron | Cast iron | 70 | 300 | 0.0016 | 200 |
| Brass 360 (free-cutting) | Brass / bronze | 200 | 500 | 0.0020 | 100 |
| Copper C110 (ETP) | Brass / bronze | 150 | 400 | 0.0020 | 50 |
| Acetal (Delrin) | Plastic | 400 | 1,000 | 0.0025 | — |
SFM is the recommended surface speed in surface feet per minute; carbide runs faster than HSS. Chip load is the starting feed per tooth shown for a 1/4 in end mill; smaller tools take less and larger tools take more. Hardness (HB) is the approximate Brinell hardness shown for context.
How to read this
Pick your material, read the surface speed for your tool material into the surface speed calculator to get RPM, then take the chip load into the chip load calculator for a feed rate. The feeds and speeds calculator does both at once. Always start a little under these numbers on a light or flexible setup and climb up once the cut proves stable.