cracks in bowls

[Brian Grenia]

Finally,
Some of the bigger bowls in the nested sets are checking slightly or have imperfections (soft spot/knot). From a lack of more knowledge/experience I have just been filling with CA before I put on the Anchor Seal. Is this ok?

When I finish the bowls, will the CA glue screw up the finish. I don't want the cracks to get worse while the bowls dry or do I. Do you just let the cracks run the course while drying and address later???

Thanks

 

[MichaelMouse]

Depending on the location of the cracks and the orientation of the annual rings, they may open, close, or remain the same. Nothing you can do with CA is going to change that, in my experience. If the bottoms are very broad and the walls thick, they'll pop. If the rim has a heart check in it already and the rings are small, or if you left the whole wall too thick or vertical, they'll crack.

Don't know what the relative humidity is where you're storing them, but it sounds wet if you're getting mildew. That's the black spotting. You're real thick there. I go around an inch at sixteen, personally. But if they're confined to the endgrain, you might just get by if they dry to 16-18 per cent rapidly enough. the endgrain will not shrink, the sides will. can be as much as a quarter inch will come off.

This diagram from the Wood Handbook shows which direction the wood moves with various grain orientations. If your cracks are on the outside of the curves, they'll open. If on the inside, they'll close. Purely a mechanical thing. http://i35.photobucket.com/albums/d160/GoodOnesGone/LogEnd.jpg

These show the changes for a heart up configuration.
http://i35.photobucket.com/albums/d160/GoodOnesGone/Picture-Package-14.jpg

From the end, as in the diagram
http://i35.photobucket.com/albums/d160/GoodOnesGone/Edge-Droop.jpg

Or, more visibly http://i35.photobucket.com/albums/d160/GoodOnesGone/1-Oak-Distorted.jpg

Compare these to what happens to yours and see what modifications you might want to make. Leave the pieces standing on their edges if possible, so everything gets a shot at the air. http://i35.photobucket.com/albums/d160/GoodOnesGone/IMG_1454.jpg

 

[Dave W]

Michael,

Are these your rough out's in the pics? If so, is there a reason for leaving the cone in the center while drying? I have not tried this myself and was curious if it makes any difference in the drying process.

 

[Greg Keddy]

Michael,

Are these your rough out's in the pics? If so, is there a reason for leaving the cone in the center while drying? I have not tried this myself and was curious if it makes any difference in the drying process.

They're bundt cake pans

 

[MichaelMouse]

Michael,

Are these your rough out's in the pics? If so, is there a reason for leaving the cone in the center while drying? I have not tried this myself and was curious if it makes any difference in the drying process.

Not in the process of drying, if you discount the fact that it keeps me from nesting and mildewing pieces. It's the artifact of the pin chuck or pin jaws that I use for working bottom out from the headstock.

I've got a 1" pin chuck I got from bestwoodtools that I use for an easy mount on anything I can turn over the bed. http://i35.photobucket.com/albums/d160/GoodOnesGone/Chuck-Sheet.jpg Bore a 1" hole it will bottom in, and the rotation of the lathe locks the roll pin. Safe, because a dismount isn't possible, and makes the job of putting a mortise in the bottom a cinch as well. I then hollow, leaving the pillar in, because it becomes most useful on the cured blank. Allows me a between-centers operation, which is a much safer way of doing things.

Since the wood shrinks across the grain but stays the same along it, it's easy to drop a 1" bit in to ream the old hole, and mount for re-turning the outside when cured. http://i35.photobucket.com/albums/d160/GoodOnesGone/Chuck-Sheet.jpg Not only is it still a safe and convenient setup, it's also mounted within a 16th of the old center, which means the mortise is simply re-rounded to hold and invert.

After chucking in regular jaws, hollowing proceeds with the tail center in play until the last moment, when the piece is at its best balance and lowest weight. http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-Two.jpg.

Shallow pieces, or low initial weight stuff is done on the pin jaws, same way. http://i35.photobucket.com/albums/d160/GoodOnesGone/Four-Quarter-Pin-Jaws.jpg Haven't used my faceplates for anything but jam chucks in years.

Yes, I know this violates the uniform thickness, sides and bottom "rule" of roughing, but that rule is silly anyway. Also allows a much thinner wall than the 10 percent "rule" when I care to, because I know that relatively straight-grained pieces will be centered spot on when cured. So I guess it does help the drying. Half as thick dries 3 times as fast.

 

[john lucas]

I used to do the sort of the same thing. I mounted my bowls between centers to rough turn. I would turn them around to hollow out the inside and leave the center cone. This made it very easy to remount between centers when they were dry so I could true up the tenon and turn the outside.
Then I would mount it in my chuck and either break off or turn away the inside cone and hollow the inside.
I don't do that any more. I rough out the inside completely now. When I put it back on the lather after it's dry I simply put a rubber sink stopper over my chuck and bring the tailstock up to the center point on the bottom left by the firs turning. This lets me true up the tenon and turn the outside. For bowls too deep to fit over the chuck without hitting the headstock I have have a scrap piece of wood that fits in the chuck. It already has rubber glued to it to drive the wood.