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Veneering with a Clamp-and-Caul Setup
Question
Forum Responses
Always use a platen on both faces as you clamp or otherwise apply pressure. In your case, a good platen would be flat 3/4" thick particleboard cut to the same dimensions as the part you want to apply veneer to. The platen's purpose is to spread the clamping pressure beyond the footprint of the clamping device. You can make clamping cauls from some beefy and stiff solid wood material of your choice. Should be somewhere in the neighborhood of say a full 2" by 4". These cauls should be made slightly convex on the edge that will be placed against the platens. I usually make them with a 1/4" maximum bow. The purpose of the bow is so that pressure will be applied to the center of the pressing as well as the edges where the clamps will be applied. The cauls are used in pairs on the outside of the platens, one on each face, and in line with one another. Use your common sense to determine how many pairs of cauls it will take to apply enough pressure to the size of the part you are veneering. The process is:
From the original questioner: Thanks. It's good to know that somebody still wants to help by supplying information on old methods. Technology is always the best way to do things, but you almost have to be wealthy to do it. From contributor J: If you are going to go with clamps and cauls, here are a few other things to add to contributor F's advice: 1. Either wax the cauls (contributor F calls them platens - the sheet goods you're pressing between) or put waxed paper between them and the veneer. Otherwise, you're likely to find your veneer glued to them.
Crotch is one of the most difficult veneers to work with; I strongly recommend trying this method with another veneer first and deciding whether it's for you. At the end of the day, an 18" x 56" crotch mahogany panel is really a job for a press. Can you not find someone near you to press it for you?
From contributor E: I don't want to be too pessimistic, but unless you're prepared to scrap your first attempt at veneering, crotch mahogany at that, you're going to be terribly disappointed. 1. Don't use a yellow or PVA glue unless you want checks and splits in the crotch. Use a urea resin glue; this also has the benefit of a longer working time. A 2 ply lay-up would be even better.
From John Van Brussel, forum technical advisor: If this is a one time job, you can do it with cauls and clamps. If you plan on doing more veneer work, I would highly recommend investing in a vacuum press. From contributor F: Contributor E brings up a good point about two ply lay-ups when veneering crotch cuts. I don't know if it is still available, but we used to use a paper product called Yorkite as a crossband between the substrate and crotch cuts or burls. From contributor A: I wouldn't lay up crotch mahogany myself. Like a burl, the veneer has to been treated. I buy crotch on a 2 ply or 3 ply or laid on substrate. Yes, it costs a little bit more on material, but you are saving on labor and are assured of a good panel. I've been using Rogers in NY. Ask for Jim - he's taken good care of me with all exotic veneers I need. Would you like to add information to this article? Interested in writing or submitting an article? Have a question about this article? Have you reviewed the related Knowledge Base areas below? 
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