Wood Cracking Question - also centering

[David Metzman]

I found some Black Walnut freshly cut in 10.2018. I posted about it. I painted the end with sealer and stored in my garage. I just turned a piece from half a log. I turned the outside one day. The next evening, it had developed a nice crack. See picture below. I assumed being two years old, it should not crack. Should I have oiled it and or covered it with a plastic bag overnight. Do I need to turn it all in one day. BTW I superglued the crack


Also, I turned between centers, did the outside and made a tenon and then flipped it putting the tenon in a chuck in order to do the inside. When I did this it did not turn true. Whenever I flip something or remount it, it never turns true. Am I doing something wrong? Perhaps the wood is moving as seen by the crack?

Should I only rough the outside and make a tenon, flip it and then finish the outside before doing the inside all while held by the tenon?

Thanks for the advice,
David

[John K Jordan]

... I turned the outside one day. The next evening, it had developed a nice crack. See picture below. I assumed being two years old, it should not crack. Should I have oiled it and or covered it with a plastic bag overnight. Do I need to turn it all in one day. ...

David, if you can't turn a wet blank completely in one day you can cover it well with plastic wrap, bag, etc. I would spray it with water first. If you can't get to it the next day you may want to add more water since water vapor can go through plastic. Freshly cut wet wood can check and crack quite rapidly.

If you know ahead of time you can't work on it again for a few days, it might be best to coat it in Anchorseal and perhaps still put it in plastic.

I don't turn wet wood often but when I do, I will sometimes spray water on the blank if the turning takes a while and cover with plastic if I head out for lunch or to feed the llamas.

I'm sure someone will discuss the mounting - I have to rush right now to get a trailer ready to haul. There are several things you can do to get it true.

JKJ

[David Walser]

David -- John gave you good advice on turning wet wood. Allow me to address a related point: You obviously didn't think this blank was still wet. After all, it was stored in your shop for over two years, it should be dry, right? No, it shouldn't have been dry. Your post header doesn't tell us where you are, nor have you told us anything about your garage (is it heated and/or air conditioned?), but even in my climate controlled shop in Arizona, I wouldn't think a blank that thick would dry in two years. The standard rule of thumb for drying is 1 year plus an additional year for each inch of thickness. Wood dries much faster in Arizona and, I assume, it takes longer in humid locations such as Florida or Hawaii. (Which is why I never use the rule of thumb in my own shop.) Instead, I weigh a piece and keep weighing it until it quits losing weight. Then it's dry, not before. (Note: I'm NOT spending a couple of hours weighing blanks in my shop. Instead, if I think I'll use a blank soon, I weigh it and then weigh it a couple of days later. If there has been virtually no change, it's dry.)

On centering: You're not doing anything wrong. Mounting a blank in a chuck after turning the tenon will almost always require truing the blank up to get it back to round. The same is true when you take a blank out of the chuck and remount it even a few minutes later. You can improve things by mounting your chuck in the tail stock and advancing the quill to mount the blank on the tenon. They make tail stock adapters expressly for this purpose. I have one. I almost never use it because it's generally not worth the time and effort. I do use it on very small items when even a small amount of alignment can be a problem. On a bowl or even a box, it's almost never an issue.

Note: I assume you're doing nothing wrong. Obviously, you need to use care in cutting the tenon and mounting the chuck onto it. Even when you do cut a perfect tenon and do your best to mount the chuck properly, the blank will be a little off center when mounted on the lathe. There are two reasons for this: The primary reason is the tenon will compress unevenly when tightening the chuck. That will shift the blank a little one direction or another. The second reason is, even a high quality chuck, will have a little bit of run out. Even if the blank is perfectly mounted in the chuck with a perfect tenon and the wood was compressed evenly when tightening, the blank will still be slightly off center when mounted. If you're NOT cutting a good tenon or are not mounting the chuck properly, by all means start there. Just don't expect perfection. You won't achieve it.

HTH

[Reed Gray]

If you are air drying lumber to make furniture out of it, a 2 inch thick blank needs to sit for 2 years/1year per inch of thickness. Then you bring it in the shop and let it sit another 6 months to a year. Anything thicker than that never really reaches 'equilibrium', which means the outside can be dry, but the inside still has a higher moisture content because it is too thick to even out the drying. So, logs never dry all the way out until cut up, which with bowls means you can rough turn them, and then seal and let dry again for 6 months or so.

As for centering, When I reverse things, they almost never run perfectly true. If I can get less than 1/16 inch of run out on a 12 inch blank, that is pretty good. 1/16 equals +/- 1/32 of an inch which is pretty close. Depending on how good you are with your tools, you can get better results with very dainty cuts. Some times I use a gouge, but most of the time now days, I am using a NRS (negative rake scraper) to shape the shoulder. I use a recess, but the same works for both methods.

robo hippy

[David Metzman]

Thank you for all of the insights. Sounds like you must be correct about the wood being still wet. BTW, I was talking about the long crack starting (or finishing) on the left that formed overnight. I finished it in Mahoneys walnut oil. The wood is pretty dark. Very nice.

Just as background - I am in NJ and my garage is heated a bit but still brisk when cold outside.

Thank you for the points on centering as well.

[David Metzman]

BTW - here is the bowl finished with just Mahoneys Walnut Oil. I figured because it was walnut it is appropriate. It is 10.5 inches across the top, There is a bit of sap wood at the bottom.

bowl 12.31.20.jpg

[Don Stephan]

One time I started turning a blank cut from a tree that had been standing dead for a year or two. The tree was dropped in the fall and I cut off a section of the log within the next couple weeks. There were no visible cracks, I mounted on a screw chuck and began shaping the outside. After lab out 5 minutes I stopped to check my work, and saw a couple cracks opening up. Since even standing dead trees will lose moisture through the bark in lower humidity seasons and crack, and might gain moisture back through the bark and the wood swell in higher humiity seasons, I suspected that the crack was present but not visible because the wood had absorbed moisture in the fall and expanded, closing the crack although it was still present.

How well was the sholder cleaned up when the tenon was made? If the shoulder is not true and crisp the blank might not seat well in the chuck, leading to wobbling.

[John K Jordan]

Don't know if this was mentioned, but wood can crack from either moisture or internal stress in completely dry wood.

Turning small platter from a kiln dried 8/4 hard maple board I walked across the shop from a partially turned piece when I heard a "crack!" from across the room. There were stresses in the wood that partially turning released. It cracked another time or two before I turned through the area and executed a design change to finish the piece.

JKJ

[Reed Gray]

I guess I can add to John's comment with defects cause cracks. Specifically knots. It is not if, but when the piece will crack off of a knot. The bigger the knot, the sooner it will crack. I do have a 3 year old plate with a knot about the size of a pea. It hasn't cracked off of it yet, but a crack did appear in the bowl. It is one of those that may have been there and didn't show, or possibly it cracked just because.....

robo hippy

[David Metzman]

Perhaps I should try playing some soft music to destress the wood and hide the gouge until the last possible moment?