ARMY TM 9-6115-670-14&P H-7 Table H-5.  Materials and Specifications Specifications Description ISO AISI SAE Hardness Hardness Penetration Frequency of Use Chromium Molybdemn Steel 34CrMo4, 34CrMoS4 4137 Induction Hardening HRC 52 to 59 0.039 to 0.079 in. (1 to 2 mm) Frequent use — 1042/ 1043 Carbon Steel for Machine Structural Use C45, C45E4, C45M2 1045 1046 Induction Hardening HRC 48 TO 56 0.039 to 0.079 in. (1 to 2 mm) Rare use Table H-6.  Chamfer and Fine Finish Requirements No Chamfer Fine Finish 1 0.039 in. (1.0 mm) — 2 0.079 in. (2.0 mm) — 3 0.0102 in. (0.3 mm) — 4 0.157 in. (4.0 mm) — 5 — 500 m in. (12.5 m mm) 6 — 250 m in. (6.3 m mm)