If you are going to make taps and dies then the first question has to be can the actual parts be thread cut? As that would be likely be easier than making taps & dies.

I like that prong die. While I frequently screwcut threads above BA sizes, that is an idea to remember for the exceptional awkward case.

On 16 May 2026 at 09:44 JasonB Said:

If you are going to make taps and dies then the first question has to be can the actual parts be thread cut? As that would be likely be easier than making t

aps & dies.

I must agree, I would always prefer to cut threads where I can, but sometimes it’s difficult to hold the part in question.

Andy.

If the thread is not particularly long and just to hold a nozzle, then you might get away with a slack 1mm pitch thread as 25 tip is 1.016mm pitch

Victor Machinery in USA might help,Don’t know about shipping etc. Satisfied buyer.

I got curious and checked a few of the largest tool suppliers here in North America since they all offer a series of what are called non standard but still stocked and available taps and dies. Unfortunately 1/2″ X 25 tpi doesn’t seem to be one of them anywhere I’ve searched.

It appears your correct Bill, thanks for the correction.

Bill, looking at the picture of the 25tpi gauge and the thread I’m not entirely convinced that the thread is 25tpi – it may be the lighting in the photo or a trick of perspective.

I believe that there is a “relatively common thread of 1/2″ od x 24tpi used on pipe fittings for 5/16 ” od pipe, which would seem a possible candidate.

Please check the thread with a 24tpi gauge before you go ordering any taps or dies.

Keith

On 16 May 2026 at 21:55 Keith Long Said:

Bill, looking at the picture of the 25tpi gauge and the thread I’m not entirely convinced that the thread is 25tpi – it may be the lighting in the photo or a trick of perspective.

I believe that there is a “relatively common thread of 1/2″ od x 24tpi used on pipe fittings for 5/16 ” od pipe, which would seem a possible candidate.

Please check the thread with a 24tpi gauge before you go ordering any taps or dies.

Keith

I agree it’s not 25 TPI, definitely try 24 TPI.

Tony

I can’t say that the one pictured is 25 TPI, the alignment is way out on the LH edge unless poorly manufactured?

Tony

I agree with Keith, the pitch doesn’t look like 25 tpi. It is slightly coarser than the 25 tpi gauge, by a bit less than half a pitch over ten threads. Which is exactly what the numbers say if one assumes the thread is 24 tpi; a 16 thou difference between 24 tpi and 25 tpi over ten pitches.

While UNS threads are specials there are still standards and 1/2″-24 is listed under tables of UNS threads. As far as I am aware no Unified thread has a 25 tpi thread. My Unified thread pitch gauges don’t include 25 tpi. Nor does my industrial lathe cover 25 tpi, although it does cover 23, 24, 26 and 27.

The link provided by Jason has an M after the thread definition, so I wouldn’t be surprised if that meant metric and the thread is actually 1mm pitch.

Irrespective of the thread specification I would assume that the external threads are rolled rather than cut. So dies are unlikely to be available.

Julie

I think some people must be looking at the 1mm (25.4tpi) gauge as that looks off to me and as there are a lot of turns won’t work. The 25tpi looks very good to me. You can see each shiny crest of the thread lines up perfic with the gauge valley bottoms.