Turning part with internal thread on centers

[brandon428]

Hi all,

I have a large OD part with a 2"-20 internal thread that I'd like to turn on centers. If it didn't have an internal thread, I'd just use/fab a mandrel.

I was thinking of turning a 2"-20 external thread on a rod using nuts on both sides to tighten, and center drilling the ends. Other ideas?

 

[tq60]

Center drill a couple of bolts.

Sent from my SM-G781V using Tapatalk

 

[brandon428]

2” bolts?

 

[markba633csi]

You're on the right track- make a 2" x 20 threaded shaft to hold the work

 

[francist]

You don’t say how long your part is although I’m getting the feeling it may be fairly short in which case the rod idea would be fine. It it was longer though, more like a tube say, I would take the same approach but instead of threading a full length rod I’d just thread two shouldered plugs to go in each each end and drill centres in those. Same idea as the rod, just saves on material and threading.

 

[GeneT45]

I'd use the plugs. Threads by themselves are not good for centering (unless you don't care about how centered it is). I'd indicate the dimension you want to preserve, if that's the case, and then center drill the plugs.

GsT

 

[brandon428]

Part is about 1-1/4" long, so was thinking to use a 1-7/8" rod, leave a 1/4" shoulder, thread the rest, and then fab a nut for the other side. Turn towards the shoulder. Good idea on the plugs if the part were longer, but wouldn't save enough material to be worth the extra time.

 

[rabler]

What is your reference surface, the ID threads, or some outside feature?
If there is an external (OD) feature that is the preferred reference, I'd create and insert the rod without drilling centers in the ends, then chuck the part in a 4-jaw (copper soft-face if necessary), dial it in, and center drill the rod that way.

 

[brandon428]

The reference is the internal threads.