1 have used several of the butt-joint methods in the past, and have been looking for a better way to make one as strong and invisible as possible, and I came up with the following.

This butt-joint is made without fasteners, using just epoxy-glue, and we want to glue more than just the surfaces together, so this is what we did.

Photo 1 (click images for larger views)

Step One

Lay out the two panesl of one-eighth inch plywood to be joined and also a butt-block of the same thickness material (Photo 1)

Photo 2

Place the butt-block over the joint, and then drill through both pieces with a small drill bit (3/32 to 1/8 inch), in the marked places. (Photo 2)

Step Two

Photo 3

Now we want to ream-out the holes on the inner faces of both the panels and butt- block to a depth of the outer ply of the plywood. Use a reamer bit or a larger drill-bit as shown (Photo 3).

Photo 4

Now --- when glued together we are bonding more than just the surfaces of the plywood. We are creating a bond through all layers of the plywood. This makes the joint stronger and in my opinion the butt-block can be narrower and thus less flattening of the panel at this point.

Step Three

Photo 5

We are now ready for the epoxy. (That used in this example is from Ace-hardware) Put the epoxy on the edge of both panels to be joined, position them on the wax- paper, coat the surfaces of both the panels and butt-block being sure to fill the recessed holes. When pressing the butt-block in position you will squeeze out through the holes the excess epoxy, remove the excess before covering with another piece of wax paper and adding the ten pounds of weights (photo 4-5).

Step Four

Photo 6

Photo 7

After the epoxy has set and is still tacky, but not hard, 1 remove the weights and wax paper and scrape both sides of the joint, then replace the paper and weights leaving it until it is hard (Photo 6-7).

Photo 8

Results (Photo 8)