Straightening the bent

[LewisM]

No, I am not a psychologist/sexologist

The pinion shaft on a recently acquired older Takahashi refractor is SLIGHTLY bent - maybe 10° off true. I believe these are chromed brass pinions.

What is the best way to straighten/true it up? I was thinking to remove the knobs, and insert up to the bend juncture into a padded vice, then with light yet deft blows with a plastic mallet, TAP the bend back out very slowly.

Any other ideas?

Of course, if any of you old scroungers/hoarders have a spare old Tak pinion hiding in your parts/junque box, please let me know! This is single speed of course, with the k obs held on with single phillips head screws into the head of the pinion shaft.

[ZeroID (Brent)]

In a vice as you say but use a longish metal tube slid over the extended bent part of the shaft and gentle persuasion to move it like a long lever. Much less chance of damage and more accurate.

[traveller (Bo)]

I'd be careful with the long lever approach as you can easily apply too much pressure and bend it the other way.
My advice:
1. Put a ring of masking tape around the shaft
2. Roll the shaft on a flat surface to find out where the bend is and mark it on the tape
3. Wrap the shaft in cloths, or sandwich it between two pieces of softwood in a vice and using another piece of softwood, gently tap in the opposite direction of the bend.
4. Take of the vice and repeat steps 1-3 above until you straighten the bend (visually at least)
Bo

[MrB (Simon)]

I have straightened bent electric motor shafts with a very close fitting tube.
Slide the tube over and it will stop at the bend, a gentle tweak and the tube will slide on a little further, another gentle tweak and it will slide on a little further again... and so on. It's done when the tube slides easily past the bend.
This is good enough to allow bearings to be removed and reinstalled, your mileage may vary.
Gentle is key.

[ZeroID (Brent)]

As Mr B says, the advantage of the long tube is you can make small increments with a lot of control, more movement at the far end.
Percussive methods are more likely to result in fracture or excessive movement.

[LewisM]

Followed Brent and Simon's advice, and it took mere seconds to straighten up. I used a thick wall brass tube about 6 inches long.

Thanks for the assistance/ideas.

[ZeroID (Brent)]

Excellent !!! Phew, another $$$ saved for another toy. LOL