Tool Steel Machinability Rating Chart
Approximate machinability ratings for annealed tool steels, on the scale where the water-hardening grades W1, W2 and W5 = 100. Ratings cover the full AISI tool steel range, from O6 (125) to the high-vanadium grades (25-30).
| Tool steel types | Machinability rating |
|---|---|
| O6 | 125 |
| W1, W2, W5 | 100 (a) |
| A10 | 90 |
| P2, P3, P4, P5, P6 | 75-90 |
| P20, P21 | 65-80 |
| L2, L6 | 65-75 |
| S1, S2, S5, S6, S7 | 60-70 |
| H10, H11, H13, H14, H19 | 60-70 (b) |
| O1, O2, O7 | 45-60 |
| A2, A3, A4, A6, A8, A9 | 45-60 |
| H21, H22, H24, H25, H26, H42 | 45-55 (b) |
| T1 | 40-50 |
| M2 | 40-50 |
| T4 | 35-40 |
| M3, class 1 | 35-40 |
| D2, D3, D4, D5, D7, A7 | 30-40 |
| T15 | 25-30 |
| M15 | 25-30 |
- (a) Equivalent to approximately 30% of the machinability of B1112 free-machining constructional steel.
- (b) For hardness range 150 to 200 HB.
Table notes
Ratings are relative to the water-hardening tool steels (W1, W2, W5 = 100) in the annealed condition — a higher number means easier machining. Because the tool-steel scale differs from the constructional-steel scale, 100 here is only about 30% of B1112 (=100 on the constructional scale).
Annealing condition and hardness strongly affect machinability; grades marked (b) are rated for the 150-200 HB range. Improve machinability by specifying the annealed condition or a resulfurized variant where the grade allows it.
Reference data for comparison — confirm the delivered condition and hardness with your supplier before planning machining times.
Related reference pages
Tool steel processing & service characteristics · D2 tool steel machining guide · A2 tool steel machining & fabrication guide · Annealing & normalizing temperature chart · Tool steel heat treatment guide · O1 tool steel · D2 tool steel · H13 tool steel · Tool steel selection by application · How to select tool steels
Source: ASM Handbook, Volume 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys, Table 15 “Approximate machinability ratings for annealed tool steels” (10th ed.). Reference data for comparison — verify the delivered condition before planning machining.