On 2004-10-19, Greg wrote:
I don't know about brass pipe, but in Electrical Metallic Tubing, 1/2"
EMT has a 5/8" inside diameter. The nominal or trade size may differ

Actually .56" according to table 4 in the NEC.

0.560" is the ID of 1/2" ENT. The ID of 1/2" EMT is 0.622", or almost 5/8".

Cheers, Wayne