ASME B1.13M-2005 (R2020)

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.