If there was ever a tool invented, I probably have several of them. I love tools.
I have enclosed a link to McMaster-Carr and the item number of a tool I think every shop should have.
It can hang on nail in the corner until needed. When called on to perform, it does a wonderful job.
Although not real cheap at just under $30 clams, it can be indispensable when push comes to 'screw'.
Go to the link and type in
20375A21 in the search bar...
Thread-It Nut And Bolt Gauge http://www.mcmaster.com/ Stuart