Thank you.
1 1/2" x 20 TPI is pretty close to my measurement D38,1mm and 25,4mm/20tpi = 1,27 mm/r. I'll try to figure changegear to make that 20 tpi and try it. Maybe I should try firs ali to nominal diameter and pich and see if I have to come down from there.
This drill is first one I found and it is made in china. It's this very generic form factor and probably there are quite a few manufacturers making these for very many brands. That picture on my first post is very close to drill I have.
It's probably copy of a copy and made cheaply. There is no way to assertain which units are used....probably it is a copy of imperial drill at one point, but dimensions are probably fudged to produce aproximate on materials available.... Bearings are metric (somewhat undersize), length measurements are very close to metric, but diameters and outside dimenssions looks imperial. Therefore I tought that if there were any universal or prefered dimenssions on these machines, that could be a good starting point. Like chuck threads are imperila and pneumatic fittings are imperial.
Pretty much only imperial tap I have is for G1/8" for smal selfmade pneumatic stuff.
I'm building here just a "proof of context" from odds and ends....I got this great idea, but there are guite a few uncertainties and I don't want to thrash the better drill just yet.
Pekka