Letting roughed bowl dry on lathe o.k.?

[Alan Tolchinsky]

Hi All, I have some wood that was waxed and the bowls I've made from it all seem to warp a little after I finish them. It's not too bad so I don't mind. But I thought I'd rough one to 1/2" and let it dry out and then finish it. I have it on the lathe held by a tenon on the foot of the bowl with a plastic bag over it to slow drying. Do you see any problems letting it dry like this? Should I take it off the lathe and let it dry? Any recommendations appreciated. Alan

[James Gillespie, Jr.]

Better to take it off. The tenon will want to move as well, and if held too tightly may lead to cracking. You'll need to re-true the tenon before rechucking it.

[Matt Hutchinson]

You have the right idea about trying to slow down the drying process, but leaving it on the lathe is not my recommendation. Not only does it prevent you from being able to use the machine for a long time (it will take weeks, probably months for the bowl to dry), but the moisture in the bowl will cause the metal to rust/corrode. I left a wet walnut bowl chucked on my lathe in much the same manner several years ago. Bad idea. Intense corrosion of the chuck jaws almost made them unusable. (Walnut contains chemicals that are more corrosive than other woods, too.)

After sealing and drying a roughed bowl, you need to be able to guage the moisture content. This can be done my weight or moisture meter. I have found that guessing leads to bowls that either warp after finishing, or even while still on the lathe. So, I invested in a moisture meter, and it works great. Now I don't have the same warping issues. I leave a bowl sealed until it's about 10 to 12 percent MC. Then I turn off the sealer, and let it dry without any sealer until it has only about 6 percent MC. 6 percent is what furniture makers need wood to be at. I final turn the bowl, and things work out really well.

Of course, the meter costs about $160, but it has the potential to 'save' all your bowls. I had been turning oval bowls because the MC was about 10 to 12 percent when I tried to finish them. This was just too high. Once I started to turn off the sealer and let dry for a few more weeks, I have been having much better success.

I hope this helps.

Hutch

[curtis rosche]

problem with leaving it on the lathe is you cant turn anything else until its dry

[Steve Schlumpf]

Alan - one other thing to take into consideration is the use of a plastic bag. The bag will trap moisture and lead to the growth of mold. That's not a problem if you wanted to cause the wood to spalt but the wood has to be able to breathe in order to get rid of any moisture.

[curtis rosche]

if you get a moistre meter look on ebeay i got one that works well for only $29 that wouldve been 180

[Alan Tolchinsky]

O.K. Thanks guys. All the suggestions make sense to me. I'm going to check Ebay for a moisture meter; that was a great deal!

[Bernie Weishapl]

Alan one problem I see leaving it on the lathe is it will take more time than a day or two or even a week to dry a bowl blank if you leave them 1/2" thick. I find when I wrap my bowls in brown paper grocery bags so the wood can let the moisture escape slowly. It takes at least 6 months or longer to dry them properly. With Denatured Alcohol I find they are bone dry in 3 to 4 weeks. Matt hit the nail on the head with walnut and his chuck. I left walnut curlies on the bed of my first lathe and it still has the stains from the walnut on the bed so that is why I clean my lathe beds everytime I turn.

[Alan Tolchinsky]

I've taken it off the lathe and out of the plastic bag. Since a good quality moisture meter is so expensive I think I'll go the weight route. So, can anybody recommend an accurate scale that would work with bowls? Thank you.

BTW these blanks are pretty dry. They've been waxed and sitting around for a few months. I have no idea how green they are except there is no water flying off when turning and the shavings seem dry. Only thing I know is they're not real low moisture content as evidenced by the warped finished bowls.

[Matt Hutchinson]

I just looked at Harbor Freight Tools. I am not convinced that their big scales are accurate enough. Unfortunately, when a bowl gets down to 6 to 12 percent the weight changes very minutely. You would need a very good scale to measure these changes. When drying a bowl using the slower methods, it would be hard to tell when bowls are ready to finish.

However, with DNA, the drying process is so accelerated that once there are no noticeable weight changes for a week or two, you know you are good to go. You can start with a thinner walled blank, one closer to the finished thickness, resulting in a light starting weight. This might allow you to use the $16.00, 5000 gram scale from Harbor Freight, which would be an accurate enough scale. And you would be able to make fairly large bowls that weighed less than 11 lbs (this scale's limit). The DNA adds a little expense, but it's better then a moisture meter.

But over time, the cost of replenishing your DNA supply will quickly surpass that of buying a moisture meter.

In an ideal world, I would use the DNA with a moisture meter. This would allow for the most flexibility, but the cost may not make this practical. I hope to be using this combination of methods this summer.

Hutch

[Alan Tolchinsky]

Great ideas, thanks. There must be some other way of determining moisture content. Like: At some point you could put the bowl in a clear plastic bag and see if any moisture settles on the inside of the bag. Any other ideas for measuring moisture content without expensive tools?

[Richard Madison]

The U.S. Postal Service sells a couple of fairly modestly priced electronic digital scales that read to nearest 0.1 ounces. I have the 10# size and it seems to work well.

[Clem Wixted]

Russ has a very inexpensive and accurate method to test the moisture content.

He says to hold the piece of wood to your cheek. If it feels cold it is still wet. If it doesn't feel cool it is dry enough to turn.

That is a paraphrase of his method.

If you want a treasure of woodturning knowledge tour Russ's site:

http://www.woodturnerruss.com/Index.html

Clem

Great ideas, thanks. There must be some other way of determining moisture content. Like: At some point you could put the bowl in a clear plastic bag and see if any moisture settles on the inside of the bag. Any other ideas for measuring moisture content without expensive tools?

[Gordon Seto]

Ditto on the scale method. It is cheap and convenient. Just jog down the weight wit pencil. It would be dry if it stops losing weight.

With moisture meter, you may be measuring mostly the surface MC. With flat works, it may be difficult to weight, then you will have to use the meter.

[Alan Tolchinsky]

Thanks guys, that "wood to cheek" method sounds interesting. I"ll give that a try and maybe buy a scale.