Today one client asked us, they ordered 1 3/4-12 UN-2A ring gage, but they received 1 3/4-12 UNF 2A ring gauge. did they received the correc gauge? here I need to conform that they received correct gauge. Both of them, TPI is 12, so pitch is about 2.1167, they have same pitch. Sometimes it is marked 1 3/4-12 UN 2A, sometimes it is marked 1 3/4-12 UNF 2A, it doesn’t matter, it is same.

Another client ask whether 2-3/4-16 UNF-2B thread plug gauge is same with 2-3/4-16-UN-2B GO/ NO GO plug gage. Here I confirm, yes it is same. The TPI is same, TPI16, so the pitch is same, it is 1.5875. Why is it marked 2 3/4-16 UNF sometimes? Because it is threads number=16 per inch, it belong to fine threads, so sometimes it is also marked 2 3/4-16 UNF 2B plug gauge.