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Mandrel wobble in the middle

Midnight_Turner

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Miles
So you all know I have a new lathe, a new compression mandrel and I've done two or three pens fine, but now it's decided to start wobbling in the middle - what the heck am I doing wrong this time??


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Penpal

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To be able to sit alongside you is totally impracticable.

Time to turn between centres mate you do not need the other drama at this stage.

Peter.
 

Graham_C

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In my limited experience Miles, over-tightening the mandrel or too much pressure from the stock can bend the mandrel.

I turn between centres now :thumbs:
 

21William

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Have you over tightened the tailstock and bent the mandrel shaft? It's easily done if you're not careful.

Using a mandrel saver will help prevent this in future or you could turn between centres.
 

Midnight_Turner

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Walter

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With a compression mandrel it is near impossible to bend the mandrel by overtightening the tailstock so either the mandrel was bent in some other way, the lathe spindle is running out of true or is not properly aligned with the tailstock, or you are applying too much pressure with the rouging gouge. Without being there with you I cannot say which.
 

Penpal

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A wonderful lesson is in Pauls recent video you can see how easily he cuts , indeed he has a light touch as you can see he never over corrects when the blank slips.

To see if the mandrel is bent simply remove it let it run on a flat surface eg a table top, then you are in a position to say its straight or bent.

Always keeping an other straight mandrel is a bonus. Go between centres until you develop your technique mate. Have success.

Peter.
 

EStreet

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eb7e8435efcd05d786e8db128251056a.jpg


This between centers with bushings.
 

rayf6604

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Turning between centres means doing away with the mandrel and using a live centre in your tail stock (live centre rotates on bearings) and a dead centre in your head stock (dead centre does not rotate on bearings) and you use your bushes between the two. The dead centre becomes the drive for the set up and the whole things relies on friction to work. I have tried it a few times but I found that bushes made from certain types of steel make a horrible black dust and if it gets on your work is bugger to get off. This happens if the bushes loose friction and slip while turning.


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EStreet

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Mandrels bend easy because they are 1/4 metal rod. The pressure you use will warp them
 
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