Vibration during turning

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rtparso

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When I get to the live center end of a pen while I am turning the pen starts to vibrate. It will go into oscillations and set a pattern into the pen. If I cut real light I can over come this but that slows things down a lot. Is this normal? Is there a way to avoid this?
 
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Sounds like the mandrel is flexing under the pressure that you are applying. Sharp tools and light cuts should do the trick[:)]. Do you have a 60 degree live center? Before I got one, I had that problem too. But since using it, concentricity has improved greatly.
 
I agree with Stan. 60 degree, also known as machinist's live center. The hole in the end of the mandrel also has a 60 degree included angle, so it does not fit the woodturner's live center tip angle.

Many times I have wondered why this information is not included with the mandrels.
 
When you set the tail stock, you should be able to grasp the live center and hold it feeling some resistance. If you can't stop it with your fingers it is too tight and the mandrel may be flexing.
 
I've had something similar happen to me when I turn Corian. I think it has to do with the material and not your lathe setup. I'm guessing that someone who turns a lot of Corian can resolve this problem??
 
When you turn corian make sure that you take very light cuts and that your tools are very sharp. If the blank vibrates and is throwing chips try sharping your chisel. I have learned that I have to resharpen my tools after about three corian pens. When it is sharp the material comes off smooth and in ribbions or flakes not chips. Hope this helps.
 
I've had nasty vibration in my Jet mini lathe for while now, I think it is one of two problems (I've ruled out the above). 1) Burned out bearing in the headstock. I had a piece of birch that wasn't as perfectly centered as I thought and I hadn't seated the tailstock as well as I thought I had. I turned on the lathe, the wood slipped to WAY off center and promptly bounced the lathe across the bench before I could shut it off. Since then I've had a nasty vibration. 2) If I bring the tailstock right up to the headstock the centers are off. How do I go about "re-aligning" the centers and, if it's the headstock bearings, how do I change them?
 
I have turned alot of corian pens in the past. The same thing happened to me. What I found out was I was using too much pressure and the tool was not sharp enough. Once I lightened up and sharpend my tools the vib. went away.

Alan
 
Well thanks for the good advice. I tried a number of things tonight. Other then easing off the pressure I slowed down the lathe. BTW are tools ever sharp enough? I did check the run out on my mandrel and the run out is about .004" which is probably close to my measurement error.
 
Jason, Lou contatcted me about this:

1. Worn bearings make noise. They will also get hot.

2. Aligning the headstock is easy. Loosen the bolts that hold the headstock to the lathe bed, and snug them back by hand. Have a good live center in the tailstock. You can use a drive center in the headstock. Tap the side of the headstock with a rubber mallet until it is lined up, and tighten the bolts back.

The bearings in a Jet Mini are common metric sizes, and cost a few dollars each. Contact me if you need a source for the bearings, and instructions.
 
Jason i sell the jet midi lathe also teach on it the head stock bearings take a beating when turning greenwood for bowls have had to replace bearings because of vibration putting undue pressure on the HS from the TS will cause bearings to over heat and vibrate
some times your center pin in live center can be missed shaped replace it clem
 
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