threading concentric?

M

mark

Registered
Registered
I am making some parts that screw together the diameter is 3/8"-24 and 1/2"-28. I am having trouble threading them where they screw together they stay concentric in the X plane and Y plane. The parts have some wobble to them and I have tried single pointing them and dies in a die holder mounted to the tail stock and I am tapping the id. Can someone point me in the right direction here. I would like to hold a .001 run out on them. Only thing I have not tried is turning them between centers.
Thanks
Mark
 
Well, we need a little more information to get specific I think. Are you wanting the thread to run with an adjacent OD or ID? Or between two round parts, as in an extension of some sort based on a threaded connection? Thread to thread there will always be clearance, unless you want to enter the world of interference threads, but you can minimize it by cutting to higher class threads. Have a pictures of what you are running into?
 
I've found the best way to make extensions is to leave a closely sized shoulder just larger than the thread OD right behind the thread, and a matching counterbore in front of the female thread of the mating parts. That way you aren't depending so much on the threads being dead true, but the smooth step and c'bore. It doesn't need to be all that long, usually as long as the diameter of the parts being mated will work.
 
mark said:
I am making some parts that screw together the diameter is 3/8"-24 and 1/2"-28. I am having trouble threading them where they screw together they stay concentric in the X plane and Y plane. The parts have some wobble to them and I have tried single pointing them and dies in a die holder mounted to the tail stock and I am tapping the id. Can someone point me in the right direction here. I would like to hold a .001 run out on them. Only thing I have not tried is turning them between centers.
Thanks
Mark
Click to expand...

Mark,

If your die has a adjustment, some do, back the set screw out half a turn. This will cut a shallow thread. You can always re-tighten if it doesn't help. Check a machinist handbook for more advise. Good Luck
 
Bill C. said:
..., back the set screw out half a turn. This will cut a shallow thread. ...
Click to expand...

Bill are you referring to the set screw in the die itself? Backing that out should allow the die to close up and cut a deeper thread. Tightening it should force the die open to cut a shallower thread.

cheers Phil
 
Sounds like good advice! In conjunction with this, I'd cut the threads for a loose fit so that Tony's shoulder suggestion is more likely to be effective. Let the shoulder do the alignment w/o influence from the threads.

BTW: 0.001" concentricity is not going to be easy...


Ray


Tony Wells said:
I've found the best way to make extensions is to leave a closely sized shoulder just larger than the thread OD right behind the thread, and a matching counterbore in front of the female thread of the mating parts. That way you aren't depending so much on the threads being dead true, but the smooth step and c'bore. It doesn't need to be all that long, usually as long as the diameter of the parts being mated will work.
Click to expand...
 
If you are making the whole part, make the threads first, screw the parts together and turn to the finished diameter.

bob
 
Thanks for all the input. I tried it with the shoulder and run the part between centers and it work perfect, the shoulder made for some aggravating threading but once done was worth it.
Thanks guys
Mark
 
You must log in or register to reply here.
Back
Top