Bar length = index rating
80–100 EASY 50–79 MODERATE 20–49 HARD <20 EXOTIC
01 Brass C360
100
02 Magnesium AZ31
100
03 6061-T6
90
04 MIC-6
90
05 2024-T3
80
06 Delrin / POM
80
07 H13 Tool Steel
75
08 7075-T6
70
09 4130 Chromoly
70
10 A2 Tool Steel
70
11 C932 Bronze
70
12 Ultem (PEI)
70
13 4140 Steel
65
14 PEEK
65
15 4340 Steel
50
16 D2 Tool Steel
50
17 304 Stainless
50
18 316L Stainless
45
19 17-4PH Stainless
45
20 BeCu C172
40
21 17-7PH Stainless
35
22 Monel 400
35
23 Ti-6Al-4V
22
24 C110 Copper
20
25 Hastelloy C-276
18
26 Inconel 718
12
Fastest on the ladder
Brass C360 & Magnesium AZ31 · 100
Both tie the B1112 benchmark — chips break clean, feeds stay high.
Toughest on the ladder
Inconel 718 · 12
Index 12 of 100 — every feature is earned slowly.
Lower number = slower feeds, premium tooling, more spindle time — it's why an Inconel part costs more than its aluminum twin.