ASME B1.13M (2005)
Metric Screw Threads: M Profile
Annotation and contents
This Standard contains general metric standards for a 60 deg. symmetrical screw thread with a basic ISO 68-1 profile designated M profile. The M profile threads of tolerance class 6H/6g are intended for metric applications where inch class 2A/2B have been used. At the minimum material limits, the 6H/6g results in a looser fit than the 2A/2B. Tabular data is also provided for a tighter tolerance fit external thread of class 4g6g which is approximately equivalent to the inch class 3A but with an allowance applied. Formulation and tolerancing data is included for applications requiring other fits. Note: A 4H5H/4h6h is approximately equivalent to a class 3A/3B fit in the inch system.