I received this question in episode 4 of the Ask Brian Boggs Show:
How thick do you re-saw wood for surface or composite panels?
Well, the thickness that we re-saw it is one thing, the thickness that we dress it to is another. So the thickness to re-saw something has partly to do with how well you can control your cut on the band saw. You want to allow for whatever variance your blade wander is going to cause. But we generally saw about 20/1000ths over size. And that’s enough for our saw. And we’ll leave a tabletop about 1/8th inch thick, a tabletop veneer about 1/8th of an inch thick. For other panels, 1/16th of an inch is fine, like the side of a desk or something that doesn’t get a lot of wear and tear. The reason for going with thinner isn’t just yield, but it has to do with wood movement. It’s preferable from a stability standpoint to go with a thinner veneer, thinner than 1/8th of an inch, because the thicker the veneer, the more it tries to act like solid wood. We want it to look like solid wood, but we don’t want it to push and pull one side of the plywood, causing warpage. So, whatever the thickness is, you want to balance the same amount on both sides of the plywood so that they’ll push and pull equally.
You also want, if you’re using two species, you want similar grain orientation and similar movement. Different woods move different amounts, so you don’t want to go something like a quarter-sawn white pine on one side and a flat-sawn walnut on the other. That’s an extreme, but the idea is you want compatible movement and force on both sides of your core. So, it’s more important that you do the same thing on both sides. And also, you’ve got to be able to dimension your material down to a certain size, so if you don’t have a thickness sander, you’re limited to what your planer can do.
We’ve actually been able to greatly increase or decrease our minimum thickness through the planer by making a vacuum box that sits on the planer bed. We just put slots in the top of the box … this is a plywood box that we make. This is a three-inch thick plywood box and we hook a vacuum to the bottom of it and there are 1/4-inch slots in the top of it that are right under the cutter head, so that the Shop Vac attached to it will hold the veneer down under the cutter head and we’ve been able to actually thickness-plane 35/1000ths of an inch thick veneers in our 24-inch planer. That’s a helical head, I don’t know if you could do that with a straight knife cutter. But that’s one thing you can experiment with for getting your thickness down uniform and thinner than the typical 1/8th-inch minimum that planers can do.
