HI all,
I am the process of re-doing our fireplace mantle. The shelf will be 3″ thick. I want to use some nice quarter-sawn white oak stock I have for the facing. Will I run into trouble if I use 3/4″ plywoood (2 layers) for a core and 3/4″ hard wood for the surfaces of the shelf? I have some vague memory about gluing up plywood to hardwood being a no-no because it would causing warping because of the differences in expansion/contraction. any coments? Ideas? thanks-Eric in L.A.
Replies
Most of the advice I see here is to not glue solid wood any thicker than 1/8" to plywood. 1/10" is better. Solid wood will swell and shrink with changes in relative humidity, while the dimensions of the plywood will not change (or only change very little). The risk is that the solid wood will split, or buckle, or delaminate, or all three.
Some people have reported success with thicker solid wood, up to 1/4" IIRC, but I haven't seen anybody claiming you can glue 3/4" oak to plywood and have it hold together in the long run.
I'm guessing that a 3" thick piece of nice QS oak would be fabulously expensive, but you could glue four pieces of 3/4" oak together to get your 3". Even there you'd want to pay attention to the different shrinkage characteristics of QS and plain sawn oak.
My room mate in college 25 years ago tried that , he made a table top out of 3/4 inch oak glued to plywood.
It stayed flat for almost a week.... then ,well, let's just say at the end of the semester he threw it away.
Philip
I'm not really a woodworker, though I have "played" with it some. Could you do a "floating" 3/4" oak hardwood top by just screwing through the first layer of 3/4" plywood from the bottom into the center of the oak with maybe one or two screws (making sure the screws don't go through the top surface of the oak), then laminate the plywood to the lowest layer of plywood with glue? That way the top could expand and contract without warping. Then band the top piece by glueing hardwood oak to the top piece of oak to hide the plywood edges. Or you could "capture" the top like you'd do with a rail and stile cabinet (or breadboard-type edge of hardwood) with the rails and stiles fixed to the dbl. layer of plywood and the top piece of hardwood not fastened in any way to the plywood. Hope I'm making myself clear--and that I'm not completely full of it.
It will be fine , you are only talking about a 1 1/2 in. wide facing. That's how we build them.
Ron
Sorry posted before reading other post-
Hears what to do cut your ply a little longer and wider than you need . Glue them trim all edges to size ( So you can get a good glue joint to your facing) - glue your facing on it ( cover it with Glue don't skimp) lots of clamps you want a good glue joint.
Now unless its going to be mounted outside in the Weather or over a boiling Caldron of water or left un Finished ( Raw) it will be OK.
We have built 100's of them and Glued 3/4 thick stock to Plywood with no complaints finished with lacquer.
Ron
Edited 1/20/2005 7:00 pm ET by Ron
Edited 1/20/2005 7:02 pm ET by Ron
If he's just talking about the edge banding, I think I agree with you. But the way I read it, the top and bottom surfaces of the mantel are also going to be 3/4" oak boards laminated to a plywood core. If it's going to be more than a few inches wide, that doesn't sound to me like a good approach.
Ron (and all), thanks for the advice so far. Yes, I would like to use hardwood for all surfaces (top, face and bottom) the shelf will be 8" wide. What if I used cleats for mounting and made a hardwood "box" instead of a "sandwich then mounting the box with the open "top" placed against the wall? I would like to get the quarter-sawn while keeping the cost down.-Eric in L.A.
Edited 1/20/2005 9:13 pm ET by Eric
Why? Its a Mantel - the top bottom really wont be seen - Say If you had a 1/4 sawn 3 in. thick Oak board - the top and bottom would be the only surfaces that would show the 1/4 sawn grain you want the face edge you SEE would be Flat Sawn Grain.
No I would not laminate glue 3/4 thick hardwood face to face to ply. it will pull away cup crack junk.
you could laminate hardwood together BUT If its 1/4 swan it will be the same thing the EDGE YOU SEE will be Flat Swan.
If I had 1/4 swan Oak I would want to see it .
Eric
You're on the money in post No 6. Go with it.
Don
Thanks for the feedback, Don. I'll go with that and post a photo when it is all done. How's the weather down south? toasty and clear here in LA-Eric
Edited 1/23/2005 4:37 pm ET by Eric
Eric
Happy to help.
It's about 101*F this afternoon, heading for 106. Australia Day on Wednesday 102*- beer & a barby. Thunderstorms predicted for Thursday with a cool change. We can't wait:-)
Don
Hi Eric. I would think that attatching it with glue would probably be a bad idea. I would rout several grooves perpendicular to the long edge of the front spaced about 10" apart. Rout these grooves with a dovetail bit and then make corresponding keys that you screw down to the plywood. You will be able to slide the top onto the keys which will allow for expansion and contraction and will keep the top flat. The 3" thick face pieces I would probably just glue but I would use a glue that has a lot of give. I cannot remember what type it is but it is available at Lee Valley. Hope this helps you. Peter
Since you are already going to use plywood for the mass of it anyway, how about using an oak veneer ply for the top layer? That way the $$ face of the lamination is done for you, you get the oak look you want and if the edge will be captured in the facia noone would ever know the difference. Right? The ply will be more stable than solid wood near the dry heat of the fire so you won't have to worry about movement of two parallel surfaces. Though in LA do you actually use the fireplace much or is it more for show?
Good luck
Andy
Being a native of Seattle, the fireplaces here in L.A. are definitely show pieces....and helping with resale on the home. is there veneered plywood out there that'll give you the quartersawn look?-Eric
You can find anything if you know where to look for it. I would look for a real lumber yard in the phone book. Even some place that carries specialty woods. Not something you will find in Home Despot.Ahh Seattle... I lived in Belltown for a while. Loved it.Andy
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