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General Category => General Scroll Saw Talk => Topic started by: Judy Hunter on March 05, 2011, 07:35:18 pm
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What am I doing wrong. I love to do boxes ...But the lids warp asfter a while. How do I prvent or correct this??
This box is cut from 1/4 inch baltic birch it is about 7 inches square. the right front corner is raised.
Sure appreciate any suggestions.
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Warping is common with birch plywood, usually the twist-type of warping. Usually caused by the change in moisture content after manufacturing. Plywood almost always has a low moisture content because of the heat used in drying and gluing.
Also, instead of cutting parallel to the bark, which minimizes warp, veneer is cut parallel to the pith. This means that there is "slope of grain" which means that the wood is moving in all three directions, instead of two, as the MC changes.
The lid is "floating" since it's not attached on 3 or 4 sides like the rest of the box. I believe I read somewhere that if you're going to make a box out of plywood, to only do the bottoms and sides, and cut the lid of solid wood.
Bill
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Judy, I did the same box done with Spanish Ceder. the Spanish Ceder is prone to wrapping anyway so I made sure that the stock was stacked and stickered when not working on it. One important thing I did to help with the warping was to tape both sides of the wood to keep the moisture level equal on both sides. I glued the pattern to the top of the wood, then clear packing tape, then on the other side, I glued plane paper and then tape. With Thin woods it is important to do the same thing on both sides, so if you use mineral spirits to clean off glue residue on one side, do the other side too.
When I mounted the hinges to the box, the top did no set level, like yours. To fix this, I shimmed the hinge on the opposite side of the warp with a piece of paper folded in half. That cured the problem!
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Judy, Dan and the fat kid nailed it... :D Great advice fellas.
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Judy, Dan and the fat kid nailed it... :D Great advice fellas.
LOL!!! :D
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ROTFL!! :D
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Dan, you're a wealth of information. I sure picked up some valuable information after reading your post.
Louis
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next to all the true words that have been said I would trough in my 2c
what might be important to look at is how the wood is cut.
so, what part of the lumber does it come and how is it sawn?
there are three ways of sawing: tangential sawn(plain), riftsawn and quartersawn.
(http://www.google.nl/url?source=imgres&ct=img&q=http://www.wisegeek.com/images/quartersawn.jpg&sa=X&ei=so1zTculCsWBOq2k4b8G&ved=0CAQQ8wc&usg=AFQjCNEK-xaZWSVowH3TkOBjr18F3bWWxw)
The wood you want (with the least warping) is called quarter sawed.
this is more expensive than plain sawn wood.(rift sawn isn't used much)
http://en.wikipedia.org/wiki/Quarter_sawing
in the woodwrightshop, somewhere in the middle of the video, he explains this to.
http://www.pbs.org/woodwrightsshop/video/2900/2906.html
I guess you can't prevent warping 100% but the right wood will help us.
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Thanks guys...... guess I will think about using non plywood type wood for the topss from now on.
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maybe you could glue a 1/4" or 1/8" part in the opposite direction (on the inside) and make your own plywood.
this will prevent from warping to.
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I have made allot of wooden boxes but the way I do it won't work on a fretwork box like you show.
I usually build a solid wood box and glue all six sides so that there is NOT a separate top and then cut the top/lid off on my table saw leaving any where from 1/2" to 1" lip all around the top for hinges or a recessed fitting lid. They do not warp that way. This method also helps with grain matching on a highly figured, solid wood box.
In order to do a fret work box that way, you will have to leave a blank area all around the box (about 1/2" or more) down from the top. for the cut to be made there.
It may not always be a workable solution but, if you can do it that way, it will keep the top from warping.
Hope this makes sense.
Rog
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Yes Roger that does make sense. I will work on trying that.
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I have made boxes and installed rare earth magnets in two corners of the top which exert constant pull to counteract any tendency to warp. I cut a mantle clock out of maple which is 3 inches thick, and the front is hinged. The front wanted to warp, so I clamped it to the main body for a few days and then used magnets as the closure. Never had the problem again.
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Judy 1/4 " is very thin wood I use no less that 10mm and normally 11to 12mm and have had no problems, I use this thickness for the whole box, it is better for gluing as well
Jimbo
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Roger, that is the method my Dad used in 1967 to make toy boxes for my sinblings and I. All three of us still have them and they are still sturdy furniture.
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I have been having the same problems on some larger flat projects such as the card I made for Jaun. However, I was using hardwood, and I think it was poplar when it happened. The part that I cut stayed flat, however, when I painted the backer it started to warp as I was painting it. Now both pages of his card are warped. I even clamped them together, laid heavy books on it and it still looks terrible. The plus side to this? The card stands up nicely by itself.
The Dragon Ball Z pics that I cut were from cheap Luan ply and they did not warp. Whats the deal with that?
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Cherie, Did you use acrylic paints? They are water based. Adding water to a thin board will cause it to cup on the opposite side.
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I try to get to the lumberyard before they run the wood through either the "warper" or the "pre-warper""! I'm not always successful.
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So i guess I should not use acrylic on wood? Then what?
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I know it's a pain but I use oil base paints. It never gives me a problem. That is going to change though they are slowly phasing them out. They are not good for the enviroment. I guess I am going to have to stock pile them then. LOL :)
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Cherie-
I use acrylics for any painting that I do.
If you are really painting for a solid color finish the board with a lacquer or poly or some sort of sealer. Finish both sides of the board. As someone said earlier do the same to both sides to prevent uneven moisture absorption. Once it is dry/cured sand smooth and paint away.
If you are using the paint in a lighter coat for a more "washing" effect (so you still see the grain) I have had luck getting the back side wet while painting then it all dries out together. I don't know if there is "science" to this method or if I am just lucky.
Katie (MrsN)
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Actually Katie is correct!
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I have have been using oil base paints all my life and they work great on wood. Excellent coverage, looks great plenty of colors and I don't have to add the extra step of sealing the wood. Oil base stains are ten times better than water base.
The pain is you have to use mineral spirits to clean it up. Thats all.
Too each his own but I will take oil base over water base any day, any time. 8)
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I like oil paints, I just really hate mineral spirits. I have sensitive skin and if I get any on me or on anything I am going to touch soon I get an icky rash.
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It was warping as I was putting the paint on. I did not even have the whole thing covered or the part that was to be painted red. LOL
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For obvious reasons I am NOT getting in the middle of that one!
But it is true...what you do to one side you must do to the other when using anything 'water based'...
Old Painter Knowledge. And True Old Painters still prefer Oil based finishes!
Nitrile Gloves are CHEAP!
~~~GB~~~