Is your mandrel out of round?

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Andrew_K99

Andrew_K99

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Joined
Feb 17, 2011
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Waterdown, ON, Canada
I wasn't aware that I had an issue until I was assembling a pen and realised I had a slight out of round issue. Albeit small, I noticed it.

With my mandrel on the lathe I turned it on to see if I could see or feel anything, and I couldn't. Slightly puzzled I wanted to figure out an easy way to tell if it were out of round. I guess I could of rigged up my dial indicator but i wanted something simple.

I took a piece of wood I had laying around, 1"x1/8"x3' or so, a metre/yard stick would do the job quite well (something thin and flat). I turned the lathe on (slowest RPM) and placed the piece of wood flat with the center laying on the mandrel. The slight out of round translated into the unheld end of the piece of the wood 'bouncing' up and down ±1/8". This confirmed that my mandrel was indeed out of round

Different sections of the mandrel had different reactions and the slowest setting yield the most noticable 'bounce'. There was also a big difference when adjust the pressure from the tail stock.

I thought I'd pass this along just incase you were looking for a quick way to test you mandrel.

I think I am moving to TBC in the near future!

AK
 
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Just thinking about this. Couldn't you take the mandrel rod, lay it on a table top or piece of MDF, get down and look at it from the surface level, and roll the rod to see if there are any gaps that show???
 
Richard Gibson said:
Just thinking about this. Couldn't you take the mandrel rod, lay it on a table top or piece of MDF, get down and look at it from the surface level, and roll the rod to see if there are any gaps that show???
Click to expand...
You could, but that'd be too easy :rolleyes:. I guess if it were a very small amount it may be hard to see?
 
I used to run mine down a flat sheet of glass and had a light behind it. If I do a pen now, which is rare I go TBC. I did keep mandrel setup though for other small projects. My 'mandrel' saver, I turned down a small piece to fit in it with a mushroom head. Good for putting up against a piece to stabilize it and not leave a mark like the 90 centers.
 
This is where the TBC SHINES! There is nothing about a mandrel that has higher tolerances than a TBC on a given lathe. Mandrels are IFFY, but with experience, (mostly considerable experience) they can be good or made to turn just as true. The TBC just eliminates a lot of the speculation. Mandrels by the fact of so many parts, bring into play more factors for error. Less parts, better precision, more reliability.

But, the mandrel does allow for both ends to be turned at the same time.
 
I could check mine to see if any of them were out of round but that would involve digging em out of whatever drawer they are in the bottom of!
Just as Hanks says TBC is the way to go!
 
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