Cracks in bowl blank

[JMitch]

You will be able to tell from my question that I am new to wood turning. I have turned some pens, XMAS ornaments and 2 small bowls. I started to turn an Ambrosia Maple bowl the other day. I was able to turn the outside shape and the foot on the bottom. I then had to leave it over night, thinking that since it was "aged" wood I would be okay. I learned my lesson the next day when I went down to work on it some more and discovered several cracks in the blank. I was able to take the blank to my wood turning club and ask how to handle the situation. They gave me some great feedback on how to avoid it in the future and how to fill the cracks. I plan on using CA glue along with some walnut sawdust to fill the cracks. The question I forgot to ask was the sequence of finishing the bowl. Should I continue to turn the bowl until the shape is complete, and then fill the cracks following by sanding and finishing? Or do I need to fill the cracks now before continuing to turn it? If I fill now, will I have to stop and fill as I am turning the bowl to it's final thickness and shape?

It was also recommended that I apply some sanding sealer to the bowl prior to filling the cracks with the CA glue to avoid any discoloration from the glue.

Any help on the process I should follow would be GREATLY appreciated! Oh, and it will probably help me avoid something exploding in my face!

Thanks!

Jeff
www.gowoodzone.com

 

[Jeff Schutzman]

Cracking/Checking While Turning In Progress

Sometimes you will have to leave the blank while you are turning it, something always comes up. Unless the wood is fully dried I usually wrap the work in progress with a thick plastic bag and use a bungee cord to secure it. No need to take the piece of the lathe.

Jeff

 

[john lucas]

Jeff The best thing I've found to avoid cracks if you have to stop for any reason is to cover the piece with a plastic bag. I wouldn't do that for a couple of days because you will get mold but over night or even stopping for dinner.
In my shop the sun shines through the window in the afternoon and hits the lathe. I will cover the piece even if I stop to go to the bathroom.

 

[MichaelMouse]

Soft maple heartwood is often full of microcracks, so if you were trying to use a lot of the darker heartwood, you might have brought them with you. Always a good idea to treat any piece of thick stock as if it were green, even if you just do a courtesy week of equalization. Turn to thick and a half and weigh it, put it where the humidity isn't dreadfully low like below a heating duct (DAMHIKT) and then check it after a couple days. Usually you'll see some movement if the difference between interior and exterior was great. That's what the extra thickness was for.

I like to run the thin stuff into cracks, then paste 'em with thick and the fill. Helps keep those parts that haven't opened yet from following the lead of the exterior. You may be exposing them later, you know.

 

[Brian Hahn]

Jeff,
For surface checking like you seem have, I'd turn to final shape first, then fill the cracks. If you can wait a while, the cracks might close up on their own when the moisture content stablizes.

On the other hand, cracks that you can see daylight through should be addressed before further turning.

 

[GeorgeH]

Russ Fairfield has some comments that might help you make your decisions on gluing:

http://www.woodcentral.com/russ/russ6.shtml

 

[underdog]

A general rule of thumb when turning green is to rough turn the form to 10% of diameter - 10 inch bowl will be turned to 1" thick - then wrap the rough bowl heavily in newspaper (to slow the drying down, and help prevent cracking) and let it cure for 6 mos to a year.

That's the general idea. There are other methods of drying quicker, but there's plenty of opinions on each way of drying - ie controversy.

Some folks just turn to finished size green, sand and finish, and then just let it warp. When you do this, you should turn to a fairly thin consistent thickness.

You will eventually learn by experience though. I know I am still in process. I don't turn and process bowls the same way I did when I first started.