Screw thread terminology

Approximately. The major diameter is the nominal diameter after the allowance (intentional reduction in material to allow for clearance between male and female threads) and tolerance (acceptable manufacturing variation) have been applied.

So, for example, if you measure the OD of 1/2-13 UNC-2A thread with a micrometer it will measure from .4876 to .4985 inches.

Ned Simmons

There are several handbooks that will give you the dimensions of screw threads. Probably the most commonly used is Machinery Handbook. Check with an available drafting department. Someone should have a copy.

Jim Y

Yep. You beat me to it.

Also, the shank diameter will be about the same or a few thousands smaller.