help

[onedash]

I cut a piece of stump to practice on. Its about 10 inches or so in diameter and about 4 inches thick or so. The entire table was shaking like an earthquake was trying to destroy it. I got it roughed out into round but continues to vibrate like a crazy monster hyped on crack.

The center of the tree is off center and im guessing the wood is actually off balance. will it even out if I hollow it out a little or make it smaller???

And I have end grain between headstock and tailstock. Is that ok or bad?

[onedash]

here are a few pics. The star shaped split is the center of the trunk. I put it off center hoping it might make it look better.

[SteveR]

Newbie here too....so until more advanced advice comes along.......

I *think* most bowls are mounted vice-versa of how you did it. So the pith will run perpendicular to the bed of the lathe. Not sure if that will make a difference in the piece running true, but maybe it does if the pith area is typically heavier?

Sometimes increasing or decreasing the lathe speed will help with vibration.
Also, for initial rough out, I mount the material between the headstock and tailstock. This helped vibration hugely!

Check this guys site out: http://www.wonderfulwood.com/ under the "for tuners" button go to "Roughing a Bowl Blank on the Lathe" and he provides pics and text to learn.

I have his first video/DVD and want to get the 2nd one. IMHO The first one is worth every penny. I think they are also available at woodcraft or maybe rockler.
HTH....and thanks for your service!
Steve

[DeanKC]

A bit more experience here.

You've got all kinds of things going on here.

1. Yes, you're going to have a MAJOR pith problem.
2. No, it's not unusual to mount endgrain between centers that way, just another variation on the theme.
3. Yes, you're going to have imbalance for sure.
4. No, you're not going to change that much, but you can do some things to help.

The pith on your project is going to continue to check and will ultimately split your work unless you do something about it. You could drill it out, say 1/4" beyond the existing splits and insert a carefully turned disk of good solid wood to replace it.

If you mount wood this way, it's harder to turn, but there are definitely ways! We had a GREAT session on endgrain turning. The instructor's point was that, whenever possible, we should turn that task into NOT cutting endgrain, but cutting side grain! He proceeded to use a gouge to drill a hole in the center of his piece and then began to take a bowl gouge with a fairly steep angle and cut from the center out. Cut like butter!

Yup, you're going to have imbalance forever on that piece!! Sapwood has a very different density than heartwood. As a result, the heartwood heavy side is going to try and thrash your machine! It's like adding 25-40% extra weight to one side!! Yes, change your speed, but SLOWER, not faster.

Other than speed, sharp tools, and good technique, the other thing that you could do is to add a LOT of weight to your machine to help dampen the vibration. This is especially useful if you have a lathe that does not have low enough speeds to kill the vibration. One of my machines won't go below 700rpm and a piece this size would probably destroy the bearings on that one! Add a couple of tubes of sand and the vibration is amazingly less, and you can make much smoother cuts with a lot of ease.

Last point is that you're probably too late to save this piece. I'm guessing that this was pretty green when you started. When turning green projects, you have to do one of two things (in my experience): You either turn it to your finished thickness and make it THIN and watch it warp to its own final shape, or you turn it so that it is about 3-4 times thicker than you plan to make it as a final size, and put it in a paper bag for a few months until the moisture content equalizes. That means measuring with a guage or weighing it with a really sensitive scale and marking the results over a period of weeks or months until you get several readings at least a week apart that are all the same. Did that make any sense to you?? If not, let me know and I'll try again.

There are other drying methods that folks try to profer, but most of them are iffy, some are pretty costly, and most of them have not withstood the tests of time. The paper bag or its brother method of air drying in closed cabinets. The point is to avoid excessive, and overly quick evaporation. Gotta be slow enough to be controlled. That's also why folks use the end-grain sealers like Anchor-Seal.

[onedash]

well there are checks all over the place now. all around it. I put it back on and mess around but most of them go all the way through. I would probably have to turn it down to the size of a cd before all the checks were gone and more would probably come. But I got the a new set of pinnacle tools this morning. The 5 piece set and they were making short work of this thing. I quit though after realizing it wasnt going to work out.
The tree in my back yard was cut down this summer and there are bugs in the bark but once I knocked all that off it seemed bug free. It was dead/dying and has some black streaks and dots in the wood.
Would it be worth trying again to get something out of it? Im down to the crotch now and figure there might be some cool grain in there somewhere.
One of the them had two centers in it. Like two trunks became one.
Here is whats left of it.

[DeanKC]

It's kind of late to be responding to this. Sorry, I was unavailable for a while.

You're right in that the crotch could probably produce some nice grain. Lots of feathery stuff associated with crotch slices.

HOWEVER, if the stump is as checked up as it seems to be in your picture, you probably now have firewood. Bummer.

When you're turning green wood (did I already mention this??), you want to turn the project down to about 3/4" or 1" max thickness. Generally speaking, you want to REMOVE the pith altogether in most species. In some of the oaks and in some of the nutwoods, you can get away with turning a thin walled vessel if you have the pith running horizontally through the piece. It would sit on annular rings, the opening at the top would be through annular rings, and the pith would run left to right through the piece. Ellsworth shows several pieces that he did that with. The piece dries and warps, sometimes producing a nice shape like a liqueur bottle (St Brennan's Irish Creme and others), other times producing a piece with two unsightly protrusions where the pith has pudged out.

If you want to save your greenish wood from splitting, you have to seal the endgrain on whole log end cuts or you're going to suffer splits every time.

Do you know anything about any of the proclaimed methods for drying green wood?? If not, say so and we'll start a thread and get all the theories out there for discussion, arguement, and dissertation.