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Proper grain orientation when face gluing solid boards into thicker parts4/23
I have created some components for a piece of furniture that are milled from 8/4 stock to 1-3/4" thick x 6-1/2" wide and various lengths. In time some of the parts have cupped due to moisture change. Since the 1-3/4" edge is not that visible I am considering making my parts out of thinner stock that has been face laminated. My assumption is that 2 or more boards face laminated to achieve my 1-3/4" thickness will be less likely to cup or warp.
Is this true and if so what is the best way to orient the various boards? Should the heart side of each board be toward each other, away from each other, or should they be glued such that the cup of the growth rings are all going the same direction (heart to sap etc...)? Will more boards in the glue up increase rigidity or just waste my time?
Thanks in advance for your help. I read this site almost daily and it has been like a college education in the ways of wood.
If you are getting cupping there is some likelyhood that the boards are not properly dried. Until the MC is where it should be, the wood should not be made into anything.
I glue them up in opposing direction not in the same , one board keeps the other flat.
8/4 stock can be just fine. Buy from a reputable dealer and then verify the moisture content. Buy rift or quartersawn grain for even more stability. If you can't buy rift or Qsawn, buy wider flat sawn, and rip out the center. What was the material you used, and was it kiln dried to 6-8%?
It is common to laminate stiles & rails for interior/exterior doors. 3 piece laminates are much more stable than 2 piece. Plywood is always made with odd number plies for this reason.
Plywood is a special case because the grain orientation switches with every ply, which would create a lot of stress if they were left unbalanced. For solid wood with grain running in the same direction, the number of plies doesn't matter nearly as much. Knowing the relative moisture content of the wood you use for laminations will help avoid mismatches that will cause the finished part to move.
I agree that if you see cupping, the moisture of the wood is not very close to the moisture in the air...almost always the wood is too wet for the air. There is no need to laminate, etc...just get the correct MC.
When making laminates as you suggest, the grain orientation is not an issue...with no moisture changes in thinner material, it will stay flat in any case.
Spending $200 for a good moisture meter is my suggestion, along with a $30 Radio Shack digital device to monitor you shop's humidity.
Plywood is sometimes made with odd number of plies, but it is also made with an even number as well.