Preparing and Fitting
Preparing the Tenons
There are a few processes to go through that need to be accomplished to get the tenons ready for fitting. First, due to the size of these particular tenons, I cut them on the table saw - no fancy jigs, just a trued blade and a fence. I prefer doing smaller tenons with a handsaw, but the table saw allows for a bit more accuracy when working such a large surface.
After cutting the tenons, I mark out the haunches and where the wedges are to be fit. The wedges will be around 5/8" to 3/4" in from the end of the exposed tenon end - that gives the tenon enough material on each side that it won't split as easily as a narrow one, and still not be too wide as to be difficult for the wood to spread apart as the wedge is driven into place. At the bottom of the where the slot for the wedges, I drill a small stop hole to help keep the wood from splitting when I drive the wedges in - it breaks the grain and give the wood a place that stresses can pivot on, rather than continuing to crack as it would if the hole were not there:
The particular pieces of wood I'm using for these rails (red oak) seem especially prone to splitting, so I thought the stop holes especially prudent here. Woods less likely to split may not require them, but I usually err on the side of caution - as there is no bigger pain than to have one split during glue-up. The only cure then is to disassemble it and repair or replace the piece - and that can mean a lot of clean up or preparation to get it ready to assemble again.
After drilling the stop holes, I use a tenon saw to cut the haunches and the slot for the wedges:
I like a good, thick bladed tenon saw to do these cuts with. A thin bladed saw will not provide a wide enough slot for the wedges, and that adds difficulty to getting them installed later. This particular saw is from a batch of saws I made where I used larger saws for the steel, specifically to have a saw for purposes like this. This way, I don't worry about cutting the taper into the slots, as just the wider saw cut will do.
After sawing, I clean up the edges of the tenon with a sharp chisel:
Here's a shot of the finished tenon, complete with haunch, stop hole, and slot for the wedge - sorry for the focus quality. Notice the number "2" penciled in on the face of the rail - the same number is penciled in on the face of the board that has the mortise this tenon fits into. I always number my joints, with the number always written on the face of the pieces; this helps me to keep my assembly all in order, and that I don't mix them up and have 2 that might not fit together when I assemble the whole affair later.
Since I did these tenons using a table saw, I don't have any reason to trim their thickness or use a shoulder plane to clean up the cheeks. I used no special tenon jigs (I don't own any, anyhow), just a trued, sharp blade and fence... But that's the beauty of the machine over doing tenons this wide by hand. That sort of accuracy isn't necessary for smaller tenons, though.
On the occasions I do tenons by hand, there is always some cleanup involved no matter how careful I try to be. Then, I use either the widest chisel I have to do most of the work or a patternmaker's rasp if there is a lot of material to remove. A skewed iron block plane might work best in such a case, but I've never owned one... A straight bladed one tends to get caught up going against the grain, and is more difficult to use. One is on my list of things to get, though, I've been jonesing over a Lie-Nielsen copy of a Stanley 140 since they came out.
After that, a wide cabinetmaker's file will clean up the face of the cheeks nicely, and serve to make them flat. It's easiest if you are working to a set of scribed lines on all the edges of the tenon. A pencil line isn't enough to get that clean edge you need to work to here. It's easier to "split the line" if the line is incised into the surface of the wood, and besides, the scribed line helps reduce tear out.
For the shoulders, it's much the same story - but I use a Stanley 92 shoulder plane where cleanup is called for. The table saw had done a pretty good job, but I did need the shoulder plane where on one rail where the stop hole didn't work. The entire rail split (fortunately before glue up) and had to be glued it back together. During glue up, I got it slightly off (it slid something less than 1/32" when I clamped the 2 pieces back together. Not much, but enough to where you would see the gap in the final product. The shoulder plane worked perfectly to correct that slight misstep.
Fitting the Tenon into the Mortise
I'm finally ready to start fitting the tenons into their respective mortises. The fit is tight enough that I can start it by hand, but can't get the tenon very far into the mortise without resorting to a mallet, which I don't want to do yet. Forcing the tenon into place by using a mallet could split the wood, and I'm too far into this to want to make a piece over again.
So, I slide the tenon into the mortise as far as I can just using hand pressure, and turn it over to see what's happening inside. A quick check shows where the tenon is tight against the wall of the mortise, so I use a pencil to mark where the "high spots" of the mortise wall are located.
And yes, the floor of my shop is covered with sawdust, shavings, cutoffs, and wasted sandpaper. Lots of it. I know, I know! (You should see the bench!)
Note - use a light pressure on the pencil, as I'll want to erase the marks later, as I'll be repeating this process. Here, I see the corner isn't quite as square as it should be. It's a perfect time to use one of the planemaker's floats I made - as they are made specifically for getting into corners:
A file is another tool that can be used in place of the float. For the face of the mortise, a patternmaker's rasp can also work, though by this stage the fit should be close enough that all you need is a file. Once the corner is straightened out, I put the tenon back in, and try again - and continue repeating this process until the tenon slides almost fully into place by simple hand pressure. I don't usually mind if I have to drive it the last 1/4" or so with a mallet, as by the time it's there it's usually sized pretty close to where it should be - enough so that it shouldn't split it.
If using a mallet at all during this process, do not use a great deal of force as you don't want to damage the end of the tenon you're bashing on. And use a wood mallet, not a metal one - you do have a wood mallet, don't you? Metal hammers and mallets are simply too unforgiving in this situation. A rawhide mallet might be a good substitute, however. I have quit hitting things with my bare hands - a few years of that and I've found the hands just don't work as well as they used to... in more ways than one.
I go through each and every tenon in this manner, carefully hand-fitting each until they slide on with ease. They don't always come apart with the same ease, so keep a small scrap that fits into the mortise that you can use to drive the rail back out, when needed.