Thread milling ?

[JohnHaine]

Best if you download and look at the little app that Richard has on the Chestnut Pens website - that defines the dimensions that you need. I measured mine by clamping the tool in a vee block and careful use of a digital height gauge, it was very quick. The app is designed for metric threads so it calculates dimensions from the standard formulas - it would presumably work for UNF, but I don't think it would for imperial 55 degree forms.

[JohnHaine]

One of the benefits of using a TCT threading tool or a tap is that it already includes the flat or radius. I just used the app, chose my fit class, and it worked.

[Leadhead]

John - My caution above is born of trying to use standard 55 deg trapezoidal tips which do not always, of course, have a compatible tip radius. Tripped me up until the penny dropped, but close approximations can be found if you search. I have tried it on the CA hardened MDF only so far. But reproduced a heavy Whit. thread quite well,