I had an odd experience on the lathe yesterday!

[MichaelA Cooper]

I have a big chunk of wood I bought off Ebay a couple years ago, not sure what type of wood it is. It's a quarter cut out of a log, if that's the way to describe it. I've been wanting to turn it for a while, just always had something else in the works. Yesterday I was looking for something to do and decided to work on this. I cut it into a turnable size chunk, removed the excess. I turned it pretty slow till it was round.
Once I got it round I thought I'd be able to speed up the lathe some to get a cleaner cut, but when I did, it vibrated real bad. I thought maybe the turning wasn't round so I checked it with my calipers and it was fine. I figured the wood must have an imbalance in dryness so I just put it in the freezer, unplugged and door cracked open of course, to let it dry for a few months.
What do you folks think might be the cause of this?

[Steve Schlumpf]

Michael - could be moisture but it could also be a difference in wood densities creating an out-of-balance situation. I have had that happen a few times and end up changing the speed (variable) a little to get rid of most of the vibration and then turn it. Have had some turnings remain unbalanced even after hollowing - so sometimes its just the way the wood is going to be.

You did the right thing in that if something doesn't feel safe - STOP! You can always go back later.

[Ken Fitzgerald]

You did the only right thing. Stop and investigate.

I would look really close at it for fine cracks along the grain of the wood. I have had wood with fine cracks that ran with the grain of the wood. I'm nearly deaf but I can tell the difference when the vibration starts.

[Richard Madison]

Michael, Have read that a log stored for a long time can definitely develop a moisture imbalance. Assume severity of the condition would vary depending upon grain direction during storage and later, in use, and kind of wood.

[Bill Bolen]

Sometimes no matter what you do the piece will not balance out. Had it happen several times and never did figure out why. The last one was a bigand tall HF. Walls ended up pretty even but the piece was out of balance from the time it got mounted till I took it off...Bill...

[Nathan Hawkes]

I like turning really irregular pieces, which means things are always out of balance! In your case, I don't really know what to suggest. Firstly, tailstock support is key here, even if you have a very secure hold on the piece, or are using a faceplate. Secondly, sometimes even if a piece is perfectly round and perfectly balanced, there will be natural variations in density from one side of a blank to another. I recently finished a 15" x 8" deep bowl (sorry--my p.c. died--no pics for a while I'm afraid) that was about half burl, and half straight grained wood. The burl side was quite a bit heavier, and always settled on the bottom when allowed to coast to a stop (PM3520 uses dynamic braking). Even with the big lathe, and tailstock support, and a level floor, etc., the thing will vibrate sometimes. Its the nature of the game; do everything you can to change the situation; slow the speed down (or up--a little rpm's one way or another can help), make sure your tools are really really sharp, change your angle of attack--a diagonal pulling cut instead of push cut for example, or any other suggestions that don't involve unsafe practices. Try everything you can. Sometimes though, things just want to go awry. Good luck! ;)