 Problem Rabbeting Plywood
I'm working on a couple "fine" cabinets, and ran into a problem. I've got too much material cost and effort invested in order to ruin it now!
The outside sides are made from high-quality ¾" cherry plywood. Now I need to rabbet the back edge to accept the back, also a piece of ¾" plywood. So I'm making a rabbet that is ¾" deep and 3/8" wide.
I'm using a CMT rabbeting bit with a 5/8" bearing to give me the 3/8" cut I want, and I'm making it with two passes for depth because the teeth are not quite 3/4" long. On the first pass of about half the final depth, to my horror the plywood is blowing out! Huge gobs are torn out, making a mess of all my previous work!!
Even scribing the cut line with a carbide wheel marking gauge set to the actual depth of the first pass, it still rips out!
I used that wheel cutter (Veritas' "Graduated Micro-Adjust Marking Gauge") for other operations on the same wood, and it prevented tear-out when making dadoes on the router table. I thought I knew how to handle this wood by now.
I wonder if it has to do with balancing the router on the 3/4" ledge? Would a little side-to-side rocking cause tear-out beyond what I've set up to deal with? If I can be confidant that that is the cause, I could make a super-wide router base that spans the entire cabinet, or clamp a wide ledge against the edge, or otherwise stabilize the router.
But I don't want to guess at this late stage. I'm hoping for some expert advice in what I suppose to be a common operation.
—John |