13/64-24 Die - Source

[Johnm1]

An idea occurred to me. OP is looking for a die that is approximately 13/64-24 which as he has already said is very close to #12-24. An ideal 13/64-24 calculated using modern thread tolerances is only ~.013 inches smaller in diameter than standard #12-24.

View attachment 1140177
Inexpensive thread dies you get from Home Depot and similar are solid and most often hex in shape. Thay are primary for chasing damaged thread not necessarily for the best cutting new threads in raw material (all though they will do it).

View attachment 1140178
A proper thread cutting die usually used by a machinist is round in shape and they are often (not always) are split on one side so that machinist using the internal screw in the die and the screws on the die holder can make fine adjustments to the resulting threads diameter to make it slightly larger or smaller thread than nominal. It might be possible to take a #12-24 dies (preferable one made on a small die blank like 13/16" or 1" OD so that is it more flexible and adjust it down to the point were it cuts something approximating a 13/64-24 thread.

It might be worth a try.

That sir is a very good idea.

But first I need to determine the angle of the thread. I understand that common imperial threads are 60 degrees while Witworth threads sre either 50 or 55 degrees. I'm not sure what metric threads are. It is likely that this thread is neither imperial or Whitworth as it predates Whitworth by 50 plus years or so.

I have not been able to determine the angle from the impression I received. Casting a positive from the impression has proved a bit more difficult than I thought. Once I have a positive the best I can hope for is to be able to compare the positive to a known 60 degree thread using very high magnification.

I'm trying real hard to not recut the threads on the bottom of the cock. I'm not sure how this will resolve but I'm in no rush.

Thanks for the 'outside the box ' thinking.

 

[MachIVshooter]

An idea occurred to me. OP is looking for a die that is approximately 13/64-24 which as he has already said is very close to #12-24. An ideal 13/64-24 calculated using modern thread tolerances is only ~.013 inches smaller in diameter than standard #12-24.

View attachment 1140177
Inexpensive thread dies you get from Home Depot and similar are solid and most often hex in shape. Thay are primary for chasing damaged thread not necessarily for the best cutting new threads in raw material (all though they will do it).

View attachment 1140178
A proper thread cutting die usually used by a machinist is round in shape and they are often (not always) are split on one side so that machinist using the internal screw in the die and the screws on the die holder can make fine adjustments to the resulting threads diameter to make it slightly larger or smaller thread than nominal. It might be possible to take a #12-24 dies (preferable one made on a small die blank like 13/16" or 1" OD so that is it more flexible and adjust it down to the point were it cuts something approximating a 13/64-24 thread.

It might be worth a try.

Yeah, should be able to squeeze it down .013". But he'll need a proper die wrench for it as well, since the adjustment screw in the die only limits the amount of compression, will not close up the die. That is done with the screws on the wrench.

 

[MachIVshooter]

But first I need to determine the angle of the thread. I understand that common imperial threads are 60 degrees while Witworth threads sre either 50 or 55 degrees. I'm not sure what metric threads are. It is likely that this thread is neither imperial or Whitworth as it predates Whitworth by 50 plus years or so.

Modern metric threads have the same symmetric flank 60° form as Unified threads with root and crest radii proportionately the same. We cut them with the same tooling when not using full profile inserts, and they can be calculated using the same formula if you just convert major diameter and pitch lead to decimal inch. Our Mazak CNCs are set up in inch, so that's what we have to do, M16x1 threads, for example, get a .630" major with a .03937" lead.

Anyway, if you're just trying to make the screw fit, I wouldn't worry about matching the thread angle that's probably not any kind of standard and may not even be symmetric or perfectly matched to the female threads anyway, given the tools of the day. Just chase with the squeezed 12-24 die and try it, if it wont go, compress the die a little more and try again. Poor flank contact won't reduce the shear strength of the threads and just isn't very critical in this application.

 

[Johnm1]

Modern metric threads have the same symmetric flank 60° form as Unified threads with root and crest radii proportionately the same. We cut them with the same tooling when not using full profile inserts, and they can be calculated using the same formula if you just convert major diameter and pitch lead to decimal inch. Our Mazak CNCs are set up in inch, so that's what we have to do, M16x1 threads, for example, get a .630" major with a .03937" lead.

Anyway, if you're just trying to make the screw fit, I wouldn't worry about matching the thread angle that's probably not any kind of standard and may not even be symmetric or perfectly matched to the female threads anyway, given the tools of the day. Just chase with the squeezed 12-24 die and try it, if it wont go, compress the die a little more and try again. Poor flank contact won't reduce the shear strength of the threads and just isn't very critical in this application.

interesting. There is so much I don’t know. I’ll have to reread your post to see if I really understand it.