14 June 2016


Dear every vendor of a tap and die set.

4-40 is a UNC thread, the 'C' means "coarse".

4-48 is the UNF or "fine" thread in the #4 size.

Your inclusion of a 4-40 in your "fine" thread tapping set is wrong.


  1. I want a 1/2"-28TPI tap and die pair for a project I have in mind.

    That is apparently UNEF - Extra Fine. For some reason, that size is simply not available here, neither singly nor in any set.

    The only solution is to hire a tool maker at ~ $140 per - a little too steep for a whimsy project.

    1. This is what happens when you adopt Godless Metric! Normal everyday taps become expensive.

      That's a $30 US part here. What's shipping all the way across the other side of the planet?

      Also, I am shocked that Amazon's tendrils haven't extended out to you and give you access to the same vendors I'm looking at.


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