A tenon saw, also known as a back saw or dovetail saw, is a handsaw with a 8 to 14 inches long straight steel blade that has a strip of reinforcing steel along its top edge for extra rigidity. Its handle is shaped like a regular hand saw except it is smaller and mounted higher on the blade. Back saws usually have cross cut teeth, although smaller models used for cutting dovetails are equipped with finely sharpened rip saw teeth on 4 to 10 inch length blades.
When using the tenon saw, a greater degree of accuracy is typically required than with a normal hand saw, and this is what they are designed to accomplish. One of its main usages, of course, is for cutting tenons into supports, rails and other members into which mortises are fit. Care must be taken in sawing tenons, as the cut is used as is without cleanup; as such the cut needs to be as close to the intended cut plane as possible in terms of straightness and perpendicularity.
Using a Tenon Saw
Clamp the wood in a vise, angled away from where it will be sawn, so that you are sawing staring at one corner. Begin the tenon cut by positioning the saw at an angle of around 45 degree to the work piece. Begin the cut with a small backward stroke. Saw down to the wood’s shoulder line, then reverse the work in the vise and saw from the opposite corner down to the shoulder line.
As you saw down, the handle is gradually lowered so that the saw is nearing horizontal rather than angled. Next, stand the work upright I the vise and join the two cuts, cutting parallel to the shoulder line. For cutting the shoulder line, put the work piece on a bench hook; keeping the saw blade parallel to the tenon and make the cut.
Tenon saws cut wood only on the forward strokes; on the return stroke the wood is only scraped by the blade. Therefore, do not apply downward pressure on return strokes, or the blade will go blunt quicker than otherwise.
Another sawing tip you should keep in mind is that it is a good practice to never make a saw cut without marking out a guideline. Use a try square, straightedge or marking gauge for laying out guidelines. For the actual mark, a pencil is adequate, but a scribing awl or knife will give more accurate results, especially when marking off measurements from a ruler, since the edge of the scribe tool can be precisely lined up with the appropriate mark on the rule. In the latter case, hold the scribe awl or knife exactly upright and look down on it vertically for optimal results.