Now that we’re back from holiday I’m pressing on with the saw bench builds. Having octagonalised the legs the next step of the build was to cut the conical tenons at the narrow end of each leg, to fit into the mortices in the bench top. I’m using the Veritas 5/8″ tapered tenon cutter and matching reamer, which have a 12.8 degree included angle (if you’re interested in that sort of thing).In The Anarchist’s Design Book Chris makes the point that you want to use the tenon cutter sparingly, and only to fair up the shape of the tenon. While it is possible to use the tenon cutter to cut the tenon from scratch, it is a painfully slow way to work, and would require having arms like Popeye. After tenoning the four legs for my first saw bench I’d have to agree with this. Although there are no “tricks” to woodworking (and I’m going to start a swear box for everytime that I say “the trick is…”), you can definitely make cutting tapered tenons easier if you remove the vast majority of the waste before you reach for the tenon cutter.
There are several stages to cutting the tenon – reducing the tapered octagon to a straight cylinder, then rough shaping the tenon, and finally bring it to true with the tenon cutter. Not having cut tapered tenons before, I decided to work my way through the first tenon from start to finish, and then try to refine the process with the other three. I’m glad I took this approach, as while the first tenon turned out fine it took a lot longer than I had expected, even though I tried to hog out as much waste by hand before using the tenon cutter.I’ve a few observations about this process:
1. I wish I had a draw knife. Or even better, that I had got round to setting up the Shopsmith I acquired last year in it’s lathe setting. The lathe would be a particularly speedy way to shape the tenons, and rigging up the Shopsmith will be an essential project for the winter. A draw knife would probably be the fastest way to remove the excess material. In the absence of a draw knife I used a spokeshave, which worked perfectly well but was much slower.
2. You can afford to be quite daring when it comes to hogging out the waste. On my first tenon I used the spokeshave exclusively to remove the waste, followed by gentle paring with a chisel, and it took forever. For subsequent tenons I shaped the cylinder by splitting off the waste with a chisel and 16oz mallet. That sounds high risk, but there are ways to make it a very controlled process.
3. Chairmakers have very different experiences of grain direction to woodworkers who mainly build flatwork. Thanks to carving guitar necks I’m relatively used to working with curves and to watching grain change direction. However, a guitar neck always has a fretboard, which means that you’re only carving 3 sides of the workpiece. On a tapered tenon you are working every side and facet of the work, which means that each tenon is likely to have a patch of difficult grain. Sharp really does fix everything though, and a keen chisel can remove highspots without tearing out if you use a slicing motion and are creative about the direction you cut from.The process I ended up using started off with cutting the shoulder of the tenon with a fine crosscut saw. I received one of the first production run of the new luthier’s saws from Bad Axe a couple of weeks ago, and this looked like the perfect opportunity to press it into servce. The whisper thin kerf perfectly defined the shoulder of the tenon, and the depth stop ensured that I didn’t overshoot the depth. I then relieved the shoulder kef by paring the waste deeply away from the kerf. This was to create a safety zone for splitting the waste away.
Ordinarily pounding a chisel into the end grain of a workpiece is a recipe for deep splits and a lot of heartache. However, by aiming the chisel carefully you can remove a lot of waste quickly, and the shoulder cuts stop the splits from travelling into the rest of the leg. This turned out to be a very efficient way to remove the waste and achieve a cylindrical tenon.Once I’d split away the waste to leave a cylindrical tenon I then used a spokeshave to taper the tenon until it was close to the final shape. The sole of the spokeshave prevented it from reaching the area adjacent to the tenon shoulder, and so I pared that area down with a sharp chisel. I also hollowed the length of the tenon very slightly with the spokeshave, so that the first turn of the tenon cutter only caught each end of the tenon – this made for an easier start and meant that the cutter was removing less material overall.
Following this process meant that I was able to tenon the remaining three legs much more efficiently (the final two took about 35 minutes each), and until the lathe is set up or I have a draw knife I think I’ll continue to take the same approach. More importantly, all four tenons are good and smooth, and are tapered to the correct angle. So all being well they will be a good fit for the mortices once I have drilled and reamed them to shape.