To make the angled-brace joints, I broke with my normal pattern of mortises-first, and began with the tenons. My reasoning was that layout would be simpler by being able to actually lay the brace in place and directly transfer the mortise locations.
Let me warn you now – if you’ve never done them, mitered mortise-and-tenon joints are a completely different animal than 90-degree ones. In principle, it should be the same thing – cut a miter on the end, take all your marks from there, and just cut. Yeah, sure. The angled tenons present a much longer shoulder and cheek than normal , and the aspect ratio is much higher. By this, I mean that the usual 45-degree cheek-cutting technique doesn’t work here. You’re basically cutting straight down parallel to the shoulder. I could feel the errors starting to multiply.
Eventually, the joints were cut and the frame halves rough-fitted. That’s when the trouble started. The mortises were simple enough, being only 1 ½” deep. The tenon shoulders were another matter. Small gaps in a joint are normal, but these were bigger than average. Additionally, a check with the try square showed that in one case I had cut my shoulders unevenly. I definitely need more practice on mitered mortise-and-tenon joints! It looked like I had my work cut out for me.
The problem with angled joints is that problems on one end tend to multiply themselves on the other. As you can see from the photos above, I seemed to have cut my miters incorrectly. This is odd, as the vertical is perfectly square with the foot, and both miters, when measured, seem to be exactly 45 degrees. . On reflection, this brace was made from the boards that had warped, and checking with a straightedge showed a very gentle curve that changed the angle of the joints to the other components. It just goes to show how little it takes to throw a couple of miters off.
The solution was to scribe both miters so that they would fit flush as presently aligned. Then, I planed to the line with my trusty large shoulder plane. This yielded a joint that, while not perfect, was much improved, and perfectly acceptable for my purposes.
Once all the joints were within acceptable limits, I drilled for drawbores. For those not familiar with the process, I drilled nearly-through holes 3/4″ from the face of the mortised pieces, inserted the tenon, and marked the tenon with the same bit. The tenon was then withdrawn, and a matching hole drilled through it. The trick is that the hole is drilled about 1/16″ closer to the tenon shoulder, creating a slight offset. This amount can vary slightly, more for softwoods, less for hardwoods. The end result is that as the peg is driven home, it pulls the two parts of the joint together in a way that technically doesn’t even need glue (I use it anyway – can’t be too careful).
For pegs, you have to be a bit careful. You want a fairly good fit for this operation, and dowels from the box store are rarely accurate. If you have a limited number of bit sizes, many woodworkers prefer to make their own pegs using a doweling plate, either “store-bought” or homemade. I have a large set of inexpensive brad-point bits that allow me to match the box-store dowels on hand, and the species of the wood wasn’t important, so I was able to use what I had. These had been rescued from a previous project that no longer served its purpose, proving this blog’s title once again. The dowels were simply cut overlong and whittled to a rounded point on one end.
I then glued up the two frame halves. As a result of repeated assembly/disassembly of the joints, they had gotten a bit of slop in them. Due to this, I decided to use epoxy instead of liquid hide glue or PVA. This should give better gap filling properties to augment the drawbores. Once the drawbores were hammered home, there was no need for clamps – the joints weren’t going anywhere. All that was left was cutting the pegs flush and cleaning everything up. As you can see from the picture below, while a little gap still remains, the joint is a vast improvement over the previous picture despite the need for a little planing.
Regrettably, I forgot to take pictures of the completed frame halves. I’m afraid you’ll just have to wait till next time for the finished product. Stay tuned!