20mm diameter Die Adapter for 1" Diameter Tailstock Die Holder

**Paul Jones** · Mar 30, 2018, 10:23 PM

I was taken by surprise during my simple addition of making the M2.5-0.45 and M3-0.5 thread gages (see the second page to http://www.homemadetools.net/forum/t...-caddy-55964-2 ) when I discovered the die diameters for cutting the treads were 20 mm and not 13/16" in diameters. I bought the dies years ago from Enco (now part of MSC) and never thought to check the diameters until I started using them. I do not have any die stocks or a lathe die stock for the 20 mm diameter dies.

I made a simple 20 mm ID sleeve from 1" dia. stainless steel 303 solid rod, bored to 20.05 mm ID, with three pass-through screw holding holes for holding the dies from the set screws in a 1" (25.4 mm) tailstock die holder.

The typical 13/16" dies are 0.8125" in diameter and the 20 mm dies are 0.7874" in diameter. Very easy to not notice the difference in diameters unless I laid one die on top of the other and looked closely to see the difference. Now that I know the difference I have found through the Internet several designs of the 20 mm diameter die stock holders for dies typically in the M2.5 to M6 ranges.