Out of Round

[jkeithrussell]

What are some of the common causes for blanks ending up slightly out of round? I made a number of pens/pencils with no problems. Lately, I've had several thicker pens that have ended up slightly out of round at the bushings. I'm not doing anything differently, so it's puzzling to me. I'm using a Jet mini (variable speed with belt drive) on a wood bench with pretty much brand new tools. Ideas?

 

[marcruby]

First check to make sure your headstock and tailstock are in alignment. Them make sure the mandrel rods are straight. I'm assuming you use mandrels. You can overtighten a mandrel, or overtighten the tailstock, or press too hard while turning. All of the above can put a kink in the mandrel guide.

 

[fernhills]

I can tell you how i solved it when it was happening to me. Just before it gets to its final diameter i back off the nut and the then snug it up by hand just enough so it don`t move when touched by cutting tools. That solved my problems of out of round.

 

[jkeithrussell]

I was thinking that I might have some vibration, so I tightened the nut and the tailstock. I bet I'm tightening them too much. I'll back it off and see how it goes. Thanks.

 

[randyrls]

Keith; All the suggestions are good ones. To determine where the problem is, mount the bare mandrel on your lathe. Turn on the lathe and hold both ends of a turning tool across the mandrel touching it. Do this at the headstock, center and tailstock end of the mandrel. If you detect any vibration, Loosen the tailstock until it is just snug. If no vibration, you are over tightening the tail stock. If there is still vibration, you have a bent mandrel or mis-aligned lathe.

If no vibration, repeat the test with blanks and bushings mounted on the mandrel. Rest the tool on the bushings ONLY! Use caution for this test. Whatever you are using must not touch the blank, only the bushings.

If the blank does not have perfectly square ends, the mandrel nut can "pull" the mandrel out-of-true if overtightened.

 

[Skye]

Bushings gone bad.
Overtightened tailstock.
Not using a 60 degree live center.

 

[Rifleman1776]

If you are using a mandrel some out of round condition is almost inevitable.
Start turning without the mandrel. Do a search here for 'no mandrel' discussions.

 

[jimbo5576]

This last week I noticed I was getting out of round turnings also. Checke all the normal items, bent mandrel, alignment overtightening and so forth. Couldn't find any obvious issues. Had the mandrel up against the 60 degree live cneter from Lil' Machine shop and absently-minded wiggled the mandrel at the tailstock end. I noticed some movement and realized the live cener itself had movement from side to side. Thought "o great, now the live center is worn out" Well I noticed there were two little holes in the retaining ring at her back of the center and put it in a wood-jawed vise, tapped it a little and the loose play was gone and so was my out of round problem. Haven't read of this before, anyone else ever had this this problem?

 

[leehljp]

Skye said it succinctly. Frank gave a great suggestion. 99% of the problems are solved in those two posts.

 

[jkeithrussell]

Thanks -- I've been looking for some information on "no mandrel" turning, but I haven't found much. Can someone point me to the right threads?

Thanks again.

 

[Skye]

I need to start some research on this myself as I'm a bit nit picker.

http://www.penturners.org/forum/showthread.php?t=38362

http://www.penturners.org/forum/showthread.php?t=37433

http://www.penturners.org/forum/showthread.php?t=36523

http://www.penturners.org/forum/showthread.php?t=36464

http://www.penturners.org/forum/showthread.php?t=7984

 

[jkeithrussell]

Thank you.

 

[heinedan]

I was having the same problem about a year ago. I threw my mandrel in the garbage, and have been turning center-to-center ever since. No more out of round pens. I feel that this is a vastly superior way of turning pens because you are only turning ond ehalf of the pen ata time. No mor edragging the gouge across the bushings or making the adjustment from one thickness level to the next. Since I switched, my pens have improved exponentially. Perfect fit with the hardware every time.

The other benefit is that you really learn to use the tool properly. If I present the tool at the wrong angle, I don't get a catch, the blank just stops turning. Aggravating at first, but I learned the right way to present the tool to the wood, and my turning is much better because of it.

I have a couple sets of bushings that are designed specifically for this method of turning. They were made by johnnycnc, but he lost all of his tools in a flood last year. Paul in OKC is currently working to take up the baton. Contact Paul for information.

I also turn Barons and Sedona the same way wth the standard bushings from AS.

Dan

 

[LEAP]

One thing that I have not seen mentioned here is to make sure your ends are square. I had one end mill that was not square to the shaft and it left the ends slightly off square. Or more precisely not evenly square as it sort of chattered and left the ends uneven. It only took a couple of pens to discover that this was causing out of round. I've stopped using mandrels so this is not a problem with out of round but would cause problems with mating the fittings if that mill was still in use.

 

[rherrell]

One thing that I have not seen mentioned here is to make sure your ends are square. I had one end mill that was not square to the shaft and it left the ends slightly off square. Or more precisely not evenly square as it sort of chattered and left the ends uneven. It only took a couple of pens to discover that this was causing out of round. I've stopped using mandrels so this is not a problem with out of round but would cause problems with mating the fittings if that mill was still in use.

Absotively posilutely! I had the exact same problem with those cheap a@# mills from China in that group buy a while back. The hole in the mill head was either too big or not centered and it made the ends of the blank off just enough to give me fits. I tried EVERYTHING until it dawned on me what the problem was. I bought 10 of those things, I don't have them any more.:wink::biggrin: