View Full Version : Threading die question

01-06-2016, 03:21 PM
Just finishing up on a lathe tail stock die holder and I have a question about the die OD sizes.

I made the holder to use 1" OD dies on one end and was going to size the other end for 1.5", but then I questioned why?

I see the larger OD's offer a greater range of thread sizes but I figure I'll single point anything over .5" diameter.

Am I missing some other reason for larger OD's?
I have to buy all the dies anyway so I'm not accommodating existing stock.

01-06-2016, 03:26 PM
Are there not some specialized threads (camera, telescope spring to mind) that are fine but large diameter? If single pointing "fine" is the issue, which might not be true.

I am not sure there are even dies for those however so they maybe a moot point...

01-06-2016, 03:39 PM
On sizes I do repeatably, I will get the die for it and get it set to just the fit I want (split dies with setscrew). Then when single pointing that thread, I go to a few thou. oversize and finish it off with the die. That gives the advantages of single pointing - straightness, concentricity, etc. - and the advantages of a die - quick and easy size control. Then I can make that thread the same exact size weeks, months, or years later without having to thread mike, use wires, or fuss around with trying to measure it every time.

01-06-2016, 05:20 PM
No, I'm talking about the OD of the die itself and the need to have a larger OD die than 1".
But, thanks anyway, I think I answered my own question.

01-06-2016, 05:43 PM
1" and 13/16" are the two common dies sizes that will cover most needs. That's all I use and I made the die holder
those sizes, one on each end.


01-06-2016, 06:18 PM
I have a few larger dies (biggest are 2" OD), some for obscure threads, mainly Whitworth and BSF, as per Toolguy's rely they're good for finishing to size or even for directly cutting - I think the larger OD is probably to allow more torque without shearing or smearing the locating screws?
The die holders (T-wrenches) for the big'uns are a bit oversize, around 2-3 feet long, so you could probably apply a couple of hundred foot-pounds by hand...

Dave H. (the other one)

Paul Alciatore
01-06-2016, 08:59 PM
No harm in leaving the other end unfinished until you have a definite need for it.