Question
I have to make a round table apron for a 60" diameter dining table. I was thinking of gluing up layers of 1/8" plywood rather than using kerfed lumber. I would then veneer over the ply. Just wondering what others recommend?
Also, is there a standard setback for the apron on a dining table? I was thinking of setting it back about three inches, so the outside diameter would be 54" on the 60" table top.
Forum Responses
(Furniture Making Forum)
From contributor J:
I've bent and laminated 1/8" Baltic birch tighter than that quite easily. However, the basic design idea presents a few problems, I think. One is that a curved apron shifts a lot of stress to the joinery between apron and leg. If you had four legs on a 27" radius apron, each section of apron would be cantilevered out nearly 8", supported by a relatively small area of joinery at each end. Would the apron support the top, or would it be the other way around?
Perhaps more importantly is the question of how many legs to use, which inevitably depends on how many people will sit at the table. A 60" table could easily accommodate six people, unless it has four legs, in which case most of those people would be short of legroom. This is why round pedestal tables are so practical.
A number of plies of similar wood (n) are glued and clamped to a curved form, which is shaped to give the lamination a deflection of "x." When the clamps are removed, the lamination springs away from the form by an amount "y."
Springback can be predicted with the formula y = x/n2. The ratio of springback to the original deflection depends only on the number of laminations. The ratio does not depend on the properties or thickness of the wood or the geometry of the curved form. Thus, for two plies, the springback is one quarter of the initial deflection, or one ninth for three plies and one sixteenth for four plies.
There is no formula for setback of the apron. It's a visual thing and your application is purely decorative.