Epoxy goes mainstream
Removing the excess
Q: Epoxy can be messy. How do you deal with squeeze-out?
A: I assemble everything rough, sanded with nothing finer than 60-grit paper. For a sculpted joint, such as between an arm and a leg, I let the epoxy cure overnight. Then I remove the squeeze-out with a die grinder, carbide grinding wheel, or a drill with a 60- or 80-grit sanding drum, as shown in the photo. Because I leave 1/16" to 1/8" extra stock to remove on curved joints for blending purposes after assembly, using a grinder or sanding drum also helps to sculpt the area to final shape. After grinding, I finish-sand the area using a palm sander with progressively finer grits of sandpaper.
For a square-edge butt joint, I remove excess epoxy using a paper towel right after clamping the parts together. When the epoxy cures, I sand the area to remove any remaining adhesive. I don't use acetone or other solvents, which can seep in and weaken joints or clog open wood pores.
Q: What types of epoxies do you use for joinery?
A: For most joinery, I use System Three's General Purpose Epoxy. (Call 800/333-5514, or on the Web at systemthree.com.) It comes with a resin and a choice of three hardeners. In winter weather, I go with their fast hardener; at normal 60 degree to 100 degree temperatures, their medium hardener works well; on really hot Texas days, I use their slow hardener. Using the appropriate hardener gives me the needed open time to spread out, fine-adjust, and clamp joints. For joints that I leave particularly loose, such as leg joints, I use System Three's T88 Structural Epoxy Adhesive instead of the General Purpose Epoxy because it's thicker and won't run out. (Because I test-fit these joints many times during construction, the loose fit reduces the chance of damaging the parts.) T88 epoxy comes with a resin and one hardener, and it cures in temperatures as low as 35 degrees.
Q: To fill gaps on surfaces, do you add sawdust to the epoxy?
A: I prefer not to do this, and here's why. I've found that the epoxy color changes when you add sawdust, particularly with mesquite, which makes a repaired area more noticeable. I've tried adding tints to get a better color match, but found this unsatisfactory too. For me, using just the basic clear amber epoxy works best.
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