# Straightening a bent rod in the lathe



## ZipSnipe (Mar 28, 2013)

Just thought I would share this trick, I was working at a tool and die shop and had a round bar sticking out to far and then my cutter was below center , needles to say it rolled over the cutter and bent.

Our resident master craftsman machinist comes over as I was pondering what to do and he said just take a hammer to it while the lathe turns. And WALA !!! short strokes with a ball peen hammer and got it back straight to with .002.

You will see it start straightening out as you hit and you should then do smaller taps with the hammer as it gets truer ...

Just thought I would share , never seen it mentioned in any of the forums I am in.

If its really bent take it out of the lather and get half way straighten out and then put it in the lathe


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## canadianhorsepower (Mar 28, 2013)

Sound good what I did I took a knurling tool replace the knurling disk with to bearing
mount that in the tool holder spin it and apply pressure come straight as an arrow


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## Swifty (Mar 28, 2013)

Similar to Luc's method, I have just put a piece of steel in the tool holder and run it against the job. Works well in most cases.

Paul.


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## Mosey (Mar 28, 2013)

I wonder if it is good for your lathe bearings to hammer on it? where does the precision go?
Mosey


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## Walsheng (Mar 28, 2013)

When I worked in a tool room we had a "beater" lathe we used for things like that. It felt the spindle had detents in it after a while.  It knocks the crap out of the bearings.

John


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## ZipSnipe (Mar 28, 2013)

I'm talking taps here not beating it to death!!!


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## Walsheng (Mar 28, 2013)

Still wouldn't do it to my lathe.  It doesn't take much to do damage.

John


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## stevehuckss396 (Mar 28, 2013)

Mosey said:


> I wonder if it is good for your lathe bearings to hammer on it? where does the precision go?
> Mosey



I was wondering the same thing. If the rod is under say 1/2 inch I might do it but over that i picture little flat spots on the bearing balls.


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## ZipSnipe (Apr 1, 2013)

Yes I should also point out that it was a 14x48 lathe I was using and the piece was probably 3/8 diameter brass tube thick wall. So like Steve said no bigger than 1/2.

On my lathe being a 9 x 20 no bigger than 3/8. I agree you could wreck your bearings if ya went a little too ape on it!!!


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## ConductorX (Apr 4, 2013)

My lathe, has a "following rest" would that work?  Or do I have my terms mixed up?







"G"


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## Tin Falcon (Apr 4, 2013)

I agree hammering on a part in the lathe not a good idea. 
gentle tapping to indicate a part in is soften needed . even that can sometimes be done with a roller too when indicating in a face. 
I d not even like conventional knurling tools too much side load on the bearings I recommend scissor knurl for the home shop. most of us have small lathes or old lathes IMHO neither deserve abuse.
Tin


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## tornitore45 (Apr 25, 2013)

I am not arguing with the OP success, but must question the method theory.
How does the hammering at a random relation to the bend direction converge to straight?


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## Bastelmike (Apr 25, 2013)

Yes, I have seen this method in practice in industry. Straightening parts on a lathe with different methods.

*BUT it is done on the oldest most worn-out lathe*. A lathe thats never again used for something with any degree of precision.
Also it is done on heavy lathes, weighing several tons. With the small lathes most of You have this practice is inappropriate 

So I only recommend doing this if You have several heavy lathes in Your homeshop and one is so worn-out that it will be sent to the scrapyard anway soon.

Mike


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## Mosey (Apr 25, 2013)

OK, what is the proper way to straighten a rod, 1/2 or so?
Mosey


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