For a piece I’m working on, and because I can’t get any decent two-faced mahogany ply, I decided to experiment with band-sawing 1/8” x 10” mahogany veneer and gluing to a ½” ply substrate. Two pieces of veneer are required for each face to end up with a 17” wide panel, 30” long. My thinking was that I would use PVC glue, veneer both sides and run them through my planer to end up with a 5/8”-11/16” board.
After band-sawing the Guatemalan mahogany, the 1/8” veneer was relatively flat. But upon applying the glue and attempting to glue to the substrate, the moisture in the glue made the veneer curve to an extent that I could not follow-through with my glue-up, despite the amount of cauls I applied. So much for that.
My thinking is that one way is to apply a two-inch wide glue-line on each panel for the middle seam with a caul, let that set and then work outwards in each direction for the next glue-up.
At the moment I’m trying another idea, which was to apply a wash-coat of glue to each panel – 75% glue/25% water – the panels being under pressure of weight until the wash-coat dries to end up with a flat panel (hopefully) that could then be subsequently glued without wanting to curve. I’ll see how that idea may work tomorrow.
Perhaps the above approach is untenable. I had thought originally of running the 1/8” veneer immediately through my planner using double-sided tape with it attached to MDF, before it started to curve where the tape would not hold the edges. I also thought of trying to cut a smaller thickness of veneer, say 1/16”, glueing to the substrate and then thickness-planning. Perhaps this is what I should try.
What I don’t want is that the seams and edges will lift after 5-75 years. Perhaps PVC glue is not the glue of choice.
All thoughts and suggestions are welcome.
I also want to take this moment to voice my appreciation for this forum and particularly to the the memory of Jon Arno who gave his knowledge to me and so many other unfailingly.
Replies
I use band sawn veneer almost exclusively. Here's some ideas. First, 1/8 inch is too thick. It's in a no man's land between solid wood and veneer. I put veneer on at 1/16" max unless it's softwood like figured redwood. Then, I scrape and sand down from there. I use titebond II most of the time and use cauls and powerful cast iron bar clamps. If a glue up is big, I use every clamp I have and clamp to the workbench. I left room for clamps under and around the top of the bench. I put a piece of veneer or two under the middle of each cross bar (1 1/4 x 3 oak on edge) to crown it.
After gluing, I clean out squeeze-out as well as possible immediately and then periodically afterwards because it is full of water and will warp the edges. I use scrapers and spatulas and a ground down butter knife (don't tell my wife!).
I usually use baltic or russian birch plywood as the substrate. If the edges are visible, I put on extra wide edge pieces after cutting the plywood to rough dimensions, then thickness sand or plane after the glue dries. Then, I veneer. To get to finished dimensions,I trim at least 1/2 inch off each side before use. Last, I cut any joinery.
PS: I have scavenged a refrigerator compressor that, when the tubes are reversed, sucks. I think that vaccum is a better idea than a billion clamps and I'm going to try vacuum veneering next veneered project. You'd need a bag and a pump. If I didn't have formalehyde sensitive asthma, I'd use unibond, a urea formaldehyde glue.
Also, are you gluing veneer pieces together into a sheet before glue up? That seems to be standard practice and works best.
Edited 3/6/2005 12:04 am ET by telemiketoo
I agree that 1/8" is too thick. 1/16" is better and easier to work with.
In addition you need to use platens as well as cauls. The platen is a 3/4" particleboard or MDF the size of your panel. The ones we used were made from melimine coated composition boards. You put on the veneer, put the platen on top of the veneer and then clamp with the cauls. Folks who veneer frequently use vacuum presses now days but platens are still used to keep the veneer flat.
First thing the veneer is too thick,1/16" is better. I would use 3/4" mdf instead of plywood. You should veneer the bottom also. I use hot hide glue,it doesn't creep like pva. There is another glue boat builders use, Cva or something like that. I haven't used it myself but I understand it is also a good glue for veneers.
You could apply glue size or maybe dampen the top surface of the veneer to reduce curling.
mike
Thanks for the replies. Yeah, I have to agree 1/8" is too thick. I'd thought 1/8" would give me plenty of leeway in my bandsaw cut. I'll try 1/16". I wish birch ply was available where I am (Mexico City) but alas it isn't. I didn't want to use MDF as some of the panels will have 3/8" tongues that go into dados and I don't think that MDF will give me the integrity that a good ply or laminboard would. I had thought of using a platen but during the glueup I realized I couldn't visually confirm that my seam was good. I'm not sure what you mean 'Telemiketoo' when you suggest that the veneer is joined before glueup.Thanks again guys for the input.Craig Caughlan
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