How to measure special threads

26 TPI . Single is .0251 so double height would be .0502 to make it easy on you . :)
 
Since my copy of Machinery’s Handbook lives at work, I use this website at home:

UN imperial screw thread calculator

theoreticalmachinist.com theoreticalmachinist.com

It will do standard as well as nonstandard diameters and pitches, and it gives tolerances for the various thread classes. It also gives the “over wires” measurements if that’s how you measure them.
 
This site gives you all the data you probably need. If your thread isn't in the pull down menu, then you can enter it in the "Basic Diameter" and "Threads per Inch" boxes.
 
Try this:
3/8-26
OD .375
Core .3340
Radius .006414
Depth .0205
Pitch .0385
Effective Dia. .3545
TPI 26
Tapping Drill 8.5mm


1/4-26
OD .250
Core .2090
Radius .006414
Depth .0205
Pitch .0385
Effective Dia. .2295
TPI 26
Tapping Drill #4

60 Degree Cycle Engineers Standard Threads
 
Here is a link to files:
anyflip.com/yafd/anxo
My copy was found on oldengine.org which is now defunct. Found a post that the new site will be:
mikeandjensoldengines.com

I printed out all the pages and keep them in a thread notebook, along with Machinery pages and any other site information. Saves a lot of time figuring out what I have. And a WHOLE LOT LESS pages then Machiery pages each time!!!!

Always looking for obscure and ancient knowledge. If any of the readers have bookmarks, please post some. I learned a long time ago that if I have a question, most likely somebody in the past already found the answer.
 
@Chewy i did find the threads from you link. I will be saving that for sure. I did not find tolerances however like class fits for it in that link.

@SLK001 @KyleG i tried there at first and it wouldn’t work but bc bozo me didn’t think i could put in different information.
 
They may not have class fits. I'm thinking that was stuff developed later on when standards became necessary. If you have the original, simply make the new ones to the same size.
 
I believe the customer is sending me nuts and some dies
 
Word of caution. Don't be surprised if the dies are carbon steel and not HSS.
 
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