Matching tap and die?


i have a slight problem figuring this one out… i am tapping
stainless steel balls w/ a 1-72 tap, and threading a rod w/ a 1-72
die to thread into the ball for body jewelry barbells… the
problem i am having is that it is EXTREMELY hard to screw the rod
into the ball… now, recently i had found a barbell that i bought a
few years ago for myself, and i noticed that the tapped hole was
slightly larger than the ones i was making myself… so my question
is, if i threaded a rod with a 1-72 die, and i threaded a hole with a
2-56 tap, will it make it much easier to screw in? or is that the way
it’s supposed to go and i just didn’t know that… i just don’t want
to waste my money on the 2-56 tap and find that the threads won’t
catch each other and be useless…

David Basile
Gen-X Jewelry

You cannot screw a 1-72 male thread into a 2-56 female thread, well
you can but only once. 1-72 means 72 threads per inch and 2-56 means
56 threads per inch. Your problem is that your pilot hole for the
1-72 tap is too small. Go to the next larger drill size (only slightly
larger) and see if that helps. What size hole did you drill?

Daniel J. Statman, Statman Designs

   so my question is, if I threaded a rod with a 1-72 die, and I
threaded a hole with a 2-56 tap, will it make it much easier to screw

No they will not engage. A 1-72 and a 2-56 are not compatible. The
72 and 56 are the threads per inch. The 1 and 2 define the diameter.
If your rod is to tight, try drilling the hole for tap 1 drill size
larger before using your 1-72 tap. That should work. Most standard
drill sizes give a 70 - 80% thread engagement. Going with a slightly
larger drill will reduce the engagement but should make it easier to
put together.

Barb & Bob McLaughlin
Taylor River Clock Works & Jewelry Designs

You didn’t say if you had an adjustable die or not. An adjustable die
is not a complete circle. One side is cut. There’s a set screw on 1
side of the cut. The purpose of the set screw is to adjust the
diameter of the threading portion of the die. If it’s an adjustable
die, unscrewing the set screw just a little (1/4 or 1/2 turn) will
make the die cut a deeper thread & consequently a smaller diameter.
This maybe enough to get the 1-72 rod to fit in a hole tapped with a
1-72 tap.

Although a 2-56 tapped hole is larger in diameter than a 1-72, the
threads don’t match & a 1-72 screw or threaded rod won’t hold reliably
if you’re even able to get it into the hole.


Are you sure the tap and die are both the same size and thread
count??? As far as I know, a 2-56 will not thread (maybe cross
thread!!!) into a 1-72 threaded hole. Are you using the correct
size drill to make the hole to be tapped? Does it tap well? Is the
rod being threaded the correct diameter? If all of this is checked
and correct, something might be amiss with either the tap or die. A
1-72 should fit a 1-72 period. You would be wasting your $$ to get a
2-56 tap. I just keep going back to the 1-72 tap or die is wrong.

Good luck.

John Dach
MidLife Crisis Enterprises
Cynthia Thomas Designs
Cynthia’s sculptures are at:
Maiden Metals,
A small bronze foundry, no web site yet!!

You have theright tap and die to go together. The idea of usig a
2-56 tap with a 1-72 die is not correct . You probably are not
running in the tap deep enough to get a full cut thread. If you look
at your tap you will see that it is tapered at the start so it does
not make a full thead until it is deeper. Taping with these very
small thread sizes can lead totap breakage very easily. Be sure to
lubricate the tap preferably with one of the special taping
lubricants. You may also have to drill deeper so that the tap can go
deep enough. You can also get bottoming taps that will go into a hole
started with a normal tap which will then tap full theads to the
bottom of the hole. Be very carefull to not break the taps on drills
in this small size. You will probably learn what I say about this in
spite of the warning… good luck Jesse

   is, if i threaded a rod with a 1-72 die, and i threaded a hole
with a 2-56 tap, will it make it much easier to screw in? or is that
the way it's supposed to go and i just didn't know that... 

No, a 72 tpi. (threads-per-inch) rod will NOT fit in a 56 tpi. hole.
Often dies are made to be adjustable with a slot and set screw usually
arranged to push the opposing side apart slightly. If you have that
kind of die and the set screw is pressing the die halves apart it will
make a larger diameter screw. In that case, loosen the set screw to
allow the die to close more and make a smaller diameter screw.

If, on the other hand, your die is not adjustable and it’s cutting a
screw that’s too big, you can carefully MAKE it adjustable by grinding
a thin slot with a cutoff wheel (aim for the non-threaded place in the
center). Then squeeze the die with handle (limit the chance of
breaking it by using a shim in the slot) and it will cut a smaller
diameter screw.

Alan Heugh