Steel M-50 AMS 6490

AMS 6490 is the aerospace material specification covering M-50 bearing steel bars, forgings and tubing, made to premium aircraft quality for bearing applications by consumable-electrode vacuum melting. Once hardened and double tempered, it reaches 62-64 HRC and keeps its hardness and rolling-contact fatigue strength up to about 700°F (371°C).

What defines AMS 6490 is its single vacuum arc remelt (VAR). The steel is air melted, then remelted once under vacuum, which strips out most of the gases and oxide inclusions that start fatigue spalls in bearing races. It’s the original, long-established aircraft M-50 spec, with a slightly wider carbon range of 0.77-0.85%. That makes it a well-proven, cost-effective choice for bearings that need premium cleanliness but don’t demand the absolute maximum fatigue life of a double-melted grade.

Typical AMS 6490 uses:

• Accessory-drive, gearbox and auxiliary power unit bearings
• Missile, rocket and actuator bearings
• Racing engine and high-performance motorsport bearings
• High-wear tooling such as cold-heading and extrusion dies

Tubing is commonly cut into ring blanks and machined into inner and outer bearing races before hardening.

For main-shaft jet-engine bearings that need the highest cleanliness, see the companion specification AMS 6491 (VIM-VAR).

Tech Steel & Materials stocks and supplies AMS 6490 bar, forgings and tubing to aerospace and defense tolerances. Request a quote for certified material cut to your size and quantity.