Threading with dies

[Rick Kirchner]

I've been trying to make some long studs (non-critical application) by turning down long bolts and then threading with a die. inevitably I end up with a thread that is off-center - one side has well developed threads and the opposite is barely into the material.

What causes this and how do I cure it?

[R. Pare]

It is most likely due to the fact that the first contact between the stud and die is against only one tooth in the die. The only way to fix this is having the stud and the die in a machine - like a lathe - that allows that first die tooth to cut and not push the stud or die sideways.

The next possibility is that the die is not perfectly square to the stud when you first start it, causing uneven cutting forces ( not centered on the stud). The die will try to make those forces equal, but 99% of the time it doesn't succeed.

[J Leonard]

Use adjustable dies. The ones with a split and can be spread. Open all the way and work your way tighter.

[Rick Kirchner]

The next possibility is that the die is not perfectly square to the stud when you first start it, causing uneven cutting forces ( not centered on the stud). The die will try to make those forces equal, but 99% of the time it doesn't succeed.

I saw that on the start and wondered. I'm thinking of tapering the nose of the stud to match the taper in the die as a means of giving it the best chance to square up.

[FVRacer21]

Take a steel or copper tube that is a snug but not tight around the stud you want to thread.
cut it about 2 “ long if possible.

using a bolt or good stud threaded into the die, put the tube over and solder the tube to the die. Now you have a guide to keep the die straight when cutting the threads.

the solder is strong and low heat so does not mess up your die.




ChrisZ

[Charlie Schmidt]

my die handle has a guide piece on one side. Kind of like a camera iris, that you set snug around the stock. Keeps it straight as the die goes down the stock. Not perfect, but it helps.

A taper on the stock can't hurt

[Lotus7]

You mentioned it was a non-critical application, would all-thread rod not work?

[pacratt]

Also beware of the die itself.
The inexpensive taps & dies you find at auto parts stores (and retail stores) are generally only useful in cleaning existing threads (i.e.- rusty bolts & nuts).
Good quality taps & dies are the answer but can sometimes be pricey.
Also, use a good thread cutting oil and look up a thread chart to see what your actual turn/bore diameter should be.
Sizing the shaft or the bore to the exact thread size will usually lead to galling & a torn up looking thread.

Just my 3.5 cents worth, after 35+ years in the trade.
Glenn

[Rick Kirchner]

I'm using these as alignment pins, so I didn't want the abrasion of all-thread on the parts.

Due to a measurement error I was actually .010 undersize on the recommended threading diameter, which I think was .370 on a 3/8-24 item.

Some good info in this thread. I spent about a half hour on youtube and found a lot of stuff about threading that I had no idea of - like the holes in the bottom of a tap for the tailstock on a lathe!