NOTE : I found it necessary to reinforce part of this design. I recommend using the improved version below instead of this one:
https://www.printables.com/model/75269-die-holder-lathe-tailstock-improved
This print is labeled experimental because I have no idea yet how well it will hold up in use. So far (Mar. 19, 2020) I have used it successfully one time to cut a 1/4"-28 thread.
This die holder is designed to work with 1" round threading dies and a lathe tailstock with an MT2 taper. The die holder section has four holes which should be tapped #10-24 for screws to hold the die (I used 1" SHCS for this). A 1/4" metal bar is used as a lever to prevent rotation (push the metal bar completely through the sleeve so it engages in both holes).
This is NOT designed to be used under power. In use, the die holder should be mounted in the tailstock, and the piece to be threaded is held in the lathe chuck which is turned manually.
As is clear from the specs, this is designed for an imperial lathe, but if anyone would like a metric version send me a message and I'll see what I can do.
Note: This print was inspired by this video by Marius Hornberger (although I ended up going with a very different design):
The OnShape 3D CAD files for this part can be found here:
My test version was printed in PLA, which so far seems strong enough.
There are two parts:
dieholder - the sleeve which actually holds the die
support - the part which fits in the tailstock and supports the dieholder
Both parts are printed with perimeters set to 12; this results in a solid print with effectively 100% infill, so the infill setting is irrelevant.
The dieholder requires supports.
The support piece does not need supports, but a brim is recommended for bed adhesion. I also raised the filament temperature by 5 degrees which gave better results for the filament I was using.
The author marked this model as their own original creation.