A tenon saw is a specific type of saw that makes tenons, which fit into mortises on another piece of wood to make a firm joint. These are some of the strongest joints, but they require exact cuts. In order to have those cuts it’s important to know how to use a tenon saw properly. It’s not too difficult, but it does require practice to master the technique.
Step 1 - Boards
Before using the tenon saw, it’s important that the ends to be cut are at a proper 90°. Start by checking these angles with a carpenter’s square. If the angle isn’t 90 degrees, you’ll have to use a miter box and a backsaw to correct this to 90°.
Check against the miter fence after this. If you can see any gaps you’ll need to use a plane on all sides so that you have absolute 90° on each side. Just take off a very small amount on each side until you’re certain all the sides are square.
Step 2 - Marking
With the sides squared you need to make the tenon depths and widths. Start by marking the depth of the tenon on the wood, and then the size of the tenon on the end of the board, all in pencil.
Step 3 - Cutting
Set up the tenon saw. With the wood held firmly in place, start by going down the short side of each tenon from the end of the board. Cut down to the depth line on the wood. You can set this on the saw, so you won’t need to use guesswork to ensure the joint is the correct depth.
After this you need to cut down the long sides, going to the same depth. To complete the making of the tenon, cut along the marks on the length of the board which will free the tenon. You might need to use a chisel to ensure that the base of the tenon is clean and at 90°. This is vital to ensure a tight fit into the mortise.
Step 4 - Sanding
You need to be sure that the sides you’ve just cut are smooth, as they won’t be after the cut. Start by going over everything lightly with rough grit sandpaper and ten slowly move through finer grits. Be sure you also sand the base of the tenon, on the board.
You want to be certain that the wood is completely smooth. Check with your fingertips to judge the smoothness of the wood. To complete, test the fit of the tenon into the mortise. If it’s too tight, you’ll need to sand down the tenon a little so it’s a good, but not overtight, fit. Sand rather than chisel in that instance as you’ll be able to take off less from the wood. Once you’re satisfied with the fit of the tenon, your job is complete.