# Turnings coming out oval shaped



## JADobson (Aug 14, 2012)

So I turned a pen for a Christmas present and once I put it together I noticed a problem. Here is the photo:









As you can see the wood is not flush with hardware. When it was on the lathe it matched the bushings perfectly and it matches the hardware on the opposite side of the pen perfectly. It appears that the blank is being turned in an oval shape so that one side matches the hardware and the other is elongated. Any ideas how or why this might be happening? It only happened on one of the blanks, the other one turned out just fine. Any help is appreciated. Here is the whole pen:


----------



## bondogaposis (Dec 18, 2011)

The wood you used must not have been completely dry. Because wood shrinks about twice as much in the tangential direction than in the radial direction round turnings will dry somewhat oval.


----------



## Jesse_Rei (May 23, 2010)

your pen mandril could be bent. happened to me once with the 7mm pens same result.


----------



## Dark_Lightning (Nov 20, 2009)

You can bow the mandrel slightly if you clamp it too tightly in the lathe. I can spring back, or may stay bowed. Roll it on a flat surface to check for bending.


----------



## wormil (Nov 19, 2011)

I agree with Bondo, it lost moisture and went oval.


----------



## marcuscraft (Nov 14, 2012)

I would guess Bent mandrel based on my experience as well.


----------



## wormil (Nov 19, 2011)

If you bend the mandrel wouldn't it be lopsided like an off center turning?


----------



## WibblyPig (Jun 8, 2009)

You may have tightened you mandrel too much. One way to check is after you finish turning, loosen it a bit and turn the bushings 90 degrees or so. Does everything still line up? If so, then you should be good.

What did you finish it with? If something water-based; WTF or the like, one side may have absorbed more than the other.

My newest favorite is turning between centers. All you need is a live center and a dead center. You turn one side at a time and you don't have to worry about mandrels, over-tightening, etc.


----------



## Wildwood (Jul 22, 2012)

Several things can contribute to out of round pen barrels pretty much up to you to figure it out and correct.

Bent Mandrel
Over tightening tailstock, or mandrel nut
Bad bushings or pen tubes not fitting squarely or too loose on bushings
Head/tailstock not aligned
Run out at headstock, bushings on mandrel
Pushing too hard while turning with dull tools


----------



## Drew224 (Jan 16, 2012)

> Several things can contribute to out of round pen barrels pretty much up to you to figure it out and correct.
> 
> Bent Mandrel
> Over tightening tailstock, or mandrel nut
> ...


I agree with this 100 percent. wood would only crack if it was wet. the biggest culprit is the bent mandrel rod and an over tightened tailstock


----------



## REO (Sep 20, 2012)

possibly wet wood. bent mandrel is a good possibility. out of line centers can bow the mandrel but the uneven cutting is from flutter that develops from the mandrel being bowed allowing the workpiece to oscillate up and down from cutting pressure. If you set up the mandrel in the headstock does the tailstock engage cleanly with out shifting the barrel of the mandrel to seat?


----------



## JADobson (Aug 14, 2012)

Thanks for all the answers guys. I'm not at home right now so I can't check anything right now but I think a bent mandrel might be a possibility. For some reason as soon as I turn on the lathe the mandrel comes loose from the morse taper causing the blanks to loosen. To counter this I was clamping down on my tailstock to keep everything tight (it didn't help). I thought I might try some loc-tite on those threads to keep it from loosening. I don't think it was wet, I'd had the blank for a year and I got it from a guy who had had it for a long time as well. Dull tools could be a problem too (Wolverine grinding jig for Christmas!!).


----------



## REO (Sep 20, 2012)

I wouldn't use the lock tight on the mandrel that is just a bandied and could cause permanent damage to the threads.


----------



## Underdog (Oct 29, 2012)

I could never get anything perfectly centered on mandrels. There's too much play between the rod, the bushings and the pen tubes…. (not to mention all the other things that have been mentioned.)

My advice?

Turn with the pen tubes between centers and ditch the mandrels. 
Dead center in the headstock and live center in the tailstock.

Go!


----------



## JADobson (Aug 14, 2012)

When you turn between centres do you just use callipers to check for the proper width? Or can you get or need special bushings?


----------



## lumberjoe (Mar 30, 2012)

Your tubes are loose on the inside. If you have enough play to be able to get thick CA or epoxy on the tubes and not push it all off when inserting in the blank, this will happen. Your blank is perfectly round, the tube isn't centered.


----------



## WibblyPig (Jun 8, 2009)

When turning between centers, you use the same bushings as usual. You just put them between the ends of the centers instead of putting them on a mandrel.

When you're ready to finish, you can take the blank off the bushings and just put the blank between the centers. Then you don't have to worry about getting your bushings all gunked up.


----------



## Underdog (Oct 29, 2012)

Unless I'm missing something, if you turn between centers you can't use the same bushings as you use on the mandrel. You either have to turn with special stepped bushings made for a perfect 60° center, or just turn with the centers in the tubes.

When using the special stepped bushings you need a lathe where the centers line up EXACTLY, or you'll have the same problem you have now. My Jet 1642 has been adjusted every which way, and tailstock replaced under warranty (twice) and I still can't get the centers to line up perfectly.

Unless I highly modify my tailstock so that it's adjustable, I don't think I'll be using my stepped bushings anytime soon.

There's also a thing call a mandrel saver tailstock center that helps keep your mandrel from bowing up. I've met with limited success on that.

So I take it back…

Rough turn on your mandrel, and then finish turn between centers to final diameter, then put your CA finish on. I normally turn a pen down slightly undersize, then build up the CA glue pretty heavy, then true it up, and sand/polish down to final diameter. And yes you have to use a caliper to check the size. That's if you really want things to be absolutely perfect. (Which I have yet to achieve…)

I'm still on the quest for a perfectly centered pen… I've gotten a lot better results, but it's never perfect.


----------



## Jim Jakosh (Nov 24, 2009)

If the finished wood is oval, either it was round when you turned it and it dried and moved out of round or the tail center in the mandrel was moving while turning.
From you explanation that only one is oval, I'd guess the wood was pretty green when it was turned.
...........Jim


----------

