I like to accent my mirror frame with decorative plugs. But they're not just for looks: Each plug hides a dowel which strengthens the half-lap joint. This technique also works for mortise-and-tenon joints. Note: I pin my joints after glue-up, but before I install the mirror.
You could simply dowel the half-lap, but dowel is frequently warped and can create gaps in the finished joint. So I use a plain Vl6-in.-dia. dowel for the joint itself, and top it with a homemade, V4-in. decorative plug. (See drawing, below.) The plug can be any shape you like; I make mine round or square.
Step 1: Drill the holes for dowel and plug. Drill the outer hole first, 1/4 in. dia. and V4 in. deep. This hole is for the plug. Then drill 3/8 in. deeper with a 3/i6-in.-dia. bit, for the dowel.
For a square plug, square up the plug hole with a '/4-in. chisel. Close-to-square is good enough here; in Step 2 you'll taper your plugs to take up any slop.
Step 2: Prepare your plug stock. Round plugs have a contemporary look. You can cut them 1/4 in. dia., using a tapered plug cutter on the drill press. Square plugs have a traditional, hand-crafted look. For these, rip an 8- to 12-in. length of plug stock, about 1/32 in. oversize in section. Then cut the plugs to length with a backsaw—each about 1/8 in. longer than the hole depth. Sand slight tapers into all four sides of each plug, so it will fill up the hole sweetly with no gaps. I use my stationary belt sander and a light touch.
Step 3: Dowel and plug the joint.
Dab some glue in the hole, and hammer home a 3/l6-in.-dia., 3/8-in.-long piece of dowel. (I use birch dowel, and I use an undersize piece of metal rod to seat it below the plug hole. In a pinch, you could seat the dowel with a screw or a bolt.) Add another dab of glue, and hammer in the the plug.
You could plane and sand the plugs flush with the frame. But I like to leave round plugs just Vl 6 in. or so proud and dome the surfaces with first 120-, then 180-grit sandpaper. And I facet square plugs with a chisel, paring in toward the center with my chisel bevel pointing down. You can do this in a random pattern, or you can clean them up precisely to form a perfect peak. —G.R.
DOWELED & PLUGGED JOINT
This two-part technique adds strength and beauty to half-laps or mortises and tenons.
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