If it's any help M40 ¡Á 1.5 is a standard metric conduit thread. Not so common yet as industry still has a long legacy of Pg threads, but you might be able to find a die that doesn't cost an arm and a leg.
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And when you start the recess shown as 13.0 diameter should be a very tight tolerance 12.00 mm. I found a slightly worn 12 mm reamer which cut 11.995 mm, gave a really snug fit on the nose. I also made my collet holders (not ER) in hard brass. Easy to machine and good enough for light use.
