About 1144 A311 CL-B|1144 steel manufactured to ASTM A311 Class B specification. This is the formal spec that covers stress-relieved, cold-drawn carbon steel bars with guaranteed minimum mechanical properties (115 KSI tensile, 100 KSI yield for Class B). This is what you're actually getting when someone says 'Stressproof' generically. The A311 process produces bars with very low residual stress, so parts don't warp when you machine asymmetric features like keyways or flats. Machines like a dream. Machinists describe it as
4140 pre-hard strength with
12L14-like machinability. Only available in round bar due to the drawing process. Not weldable. Compare to plain 1144 (same chemistry, less stress relief, cheaper),
ETD-150 (higher strength, same concept), and 4140 pre-hard (stronger but harder to machine and will move on you).
