Minimum rod diameters for a class 2A (medium class of fit) thread a

1/4-20 .2408
5/16-24 .3042


"Jim K" wrote in message
...
This may be a simplistic question but then I'm pretty simple...

My thread chart gives the OD of threads, e.g. .250 for 1/4-20 and .312
for 5/16-24.

Is it safe to assume that the OD given is the size of a rod one would
use for that size thread. Is there a rod diameter equivalent to the
75% or 100% tap drill size?