Perplexed...not sure how to finish, or start over....

[medic29]

It seems like there is a general consensus of using a collet and grabbing the threaded end, which I had considered, but wasn't sure if I would screw something up going that route. That makes the most sense to me as it would take quite a bit of the length out of the equation and provide the needed support.

I am interested in trying to straighten the original, which I had originally considered, but wasn't sure how. I had thought about using my press, but didn't for fear of messing it up. Straightening the original would be the quickest I'm thinking. Plus, for the one I'm creating, once I'm done with the lathe work I'll still need to take it to the mill to cut the key ways (something else I've never done, I haven't looked yet to see if I have the correct cutter...oops. One step at a time). I figure I'll cross that bridge of cutting the key ways once I'm successful with the lathe work.

 

[MrWhoopee]

How would I got about trying to straighten the original? I did place it in a collet chuck and turned it in the lathe to find the high area, but wasn't sure where to go from there since it involved the threaded area.

Hold it in the collet with the bend just the outside mouth of the collet. With the spindle turning at the slowest speed, use a block of wood, plastic or aluminum and push it against the shaft towards the outboard end with the tool post. Slowly advance the cross-slide as the shaft rotates. Cutting a vee in your pusher block may be helpful, but allow it to float up and down with the shaft against the toolpost. Not recommended for larger shafts, but should be no problem for something small like this.

 

[Chipper5783]

Straightening shafts is a standard shop procedure, and like anything else there are techniques (tricks of the trade). I approach such tasks carefully, since the first try usually gives the best results (after one has mangled it, it can be a real mess). Part of the challenge is that many metals strain harden, so the bent region has a higher elastic limit than the portion that did no bend (I.e. it is stronger). Go slow, map out the distortion, plan how to straighten given areas. It can work very well, I have straightened several long screws.

 

[medic29]

Hold it in the collet with the bend just the outside mouth of the collet. With the spindle turning at the slowest speed, use a block of wood, plastic or aluminum and push it against the shaft towards the outboard end with the tool post. Slowly advance the cross-slide as the shaft rotates. Cutting a vee in your pusher block may be helpful, but allow it to float up and down with the shaft against the toolpost. Not recommended for larger shafts, but should be no problem for something small like this.

The bent area is 1/2" diameter, this doesn't seem small to me, I'm thinking 1/4" or less, but compared to the threading screw on either lathe which are 3/4" or 1", I guess it is. I will definitely look into doing this.

 

[FOMOGO]

I know your already under way on the new part, but you should be able to heat straighten your original to pretty close to perfect. The new one is looking good. Mike

Edit: I see this has been mentioned already above by Chipper. I have also straightened shafting as large as 2" with good results. Just a matter of more heat (not that it takes a lot), or a bigger press. Mike

 

[markba633csi]

One way of straightening would be to mount the part in the spindle (collet, 4J, your choice) then determine where the
high spot is.
Once you know where the bend is, then you could use a piece of wood as a lever between the lathe compound and the part
with the spindle stopped, then rotating the spindle to check your progress, repeating as necessary. Once the part looks ok
to the naked eye you can check with a dial indicator. The naked eye test may be good enough

 

[Aukai]

Plug this into You Tube.
shaft straightening with heat

 

[medic29]

I've watched a couple of videos on using heat, but can I do this in a threaded area or would it somehow deform the threads with the shrinking of the metal and such? I get how it works with a solid rod/bar, but the threads will be a much thinner area and will heat up much quicker than the actual body of the bar.

 

[SLK001]

I see yellow paint on the original. Are you sure that it is bent and NOT the paint that is causing issues?

To continue with your new part, I would either find a fitting collet, or chuck it up in a three-jaw. An ACME thread should be able to spread the clamping load over the thread and not damage the thread. If you're worried about doing damage, just slip some copper shims over the jaws first, then clamp away.

 

[medic29]

I see yellow paint on the original. Are you sure that it is bent and NOT the paint that is causing issues?

The yellow paint is from me identifying the high spots with it turning on the lathe while in a collet chuck.