How to make a die using a tap

Excellent news. Can you refresh our memory of what material you'll be using the die on, and how much use the die will get? That may change the answer quite a lot. I did dig through my dies and I don't have a 12-20, but I do have a 1/4-40 LH that I'm sure is useful to someone...just not me...

Before you spend a lot of time on this I suggest you do some reading in Machinery's Handbook. Read the section on thread forms and classes for screw threads, and the material on thread forms and limits for taps and dies. If you expect male and female threads cut with your tap and a homemade die threaded with the same tap, I fear you'll be disappointed.

Ned Simmons

I've done this a couple of times, but I had a lathe handy to locate and bore the side holes to get the right clearance. I used a slice off a

1" section of O-1 drill rod. Centered it up in the lathe, bored the clearance-sized hole, then applied the tap using the tail stock and center for tap wrench support. Used plenty of the old-style, dark, smelly cutting oil, too. The ticklish part was boring the offset holes to form the cutting edges, I took measurements off the button dies I had and tried to use the same offsets on mine. Must have worked, it cuts fine. After that, I hardened the die per the instruction sheet that came with the steel and tempered it in an electric skillet for about an hour, think the temp was about 375 or so. After that, I split the edge with a Dremel cutting disk and rounded the edges off for the set screw. I did some stoning with an india stone to shaarpen the edges, too. The screws I made worked fine with the tapped holes and it seemed to cut as well as factory-made dies. I think you'll find it a challenge to get everything spot on with only a drill press and hand tools, but you could do it with luck and skill. Not sure how you'd get a blank formed with both sides parallel and the diameter even all the way. Use a hole saw and cut a slug out of some ground flat stock, maybe, mount it on a bolt and chuck it in a drill and work it down with a file. I did a lot of that in my much younger days, pre-lathe.

Stan

Excellent narrative!

Been there, done similar.

I love reading stuff like that which exemplifies expressions like:

"There's more than one way to skin a cat."

"Where there's a will there's a way."

and my favorite, from the farmers "down Maine":

"Pretty is as pretty does."

Jeff

Not really. I mean you could, but I'll give you this - my 1/2-20 tap and die do NOT fit together. The die is smaller or the tap larger, to allow clearance on the respective cut parts.

Tim

-- Deep Friar: a very philosophical monk. Website:

Tim, can you lend your die to Joel for a week, for say $5? problem would be solved. You can ask him for a deposit in case the die breaks or gets lost.

i i

Depends a great deal on what you are going to thread.

Given the size of the thread you can use a piece of drill rod [oil or water hardening ok] c. 1 inch in diameter. cut off a piece avout 1/2 inch long as square as you can. Drill tap and drill the thread. take a small three corner swiss file and cut a series of notches inside the "die," so the edge of the notch will be radial when you screw it onto what you want to thread.

harden the "die" and temper to straw color.

If what you are threading is soft and you only have one or two pieces, you can try using the die soft and even making it out of a scrap of better steel like 4140.

What uses a 12 X 20 thread?

Tim, You musta missed something. Usu. 2 or 3 relief holes are made in the proper locations and then those holes are filled in with close fitting plugs of mild steel, preferably hammered in so they will expand into a tight fit. The heads formed, if any, when hammering in the relief-hole plugs need to ground off so the plugs can be driven out. Next, the center hole is drilled and threaded with your new tap. Finally, the relief hole plugs are driven out with a punch. Viola! New die, ready for final shaping, if desired, (square is good, here) and heat treating.

I have made several tap and die combos; some custom for really strange threads but most just for the experience and being able to say, "I can do it". The largest I have is a 3/4 - 10,

Bob Swinney

I didn't see that technique mentioned before, but it would get around my concern about being able to mate the threads from such a tap and die pair. Pretty clever.

Ned Simmons

I recall reading about this technique in on old book (reprinted by Lindsay). In that account, it was suggested that the die be heat-treated before removing the mild steel plugs. It was claimed that the quench will loosen these plugs so that they will almost fall out.

It seems to me that leaving the plugs in would also help protect the cutting edges from overheating, as well as keep them from cooling off too quickly on the way to the quench tank. I always have trouble heat-treating tiny stuff.

Dave

Robert Sw> Tim,