Sawing Square: Two Lines at Once, and Fixing a Cut That Drifts

Square the line across the top face, then continue it down both edges with the try square, and across the underside if you can reach it. Now every face you can see carries the line. This costs about a minute and it converts the problem from steering blind into simply following what is drawn. It is also self-checking: if the lines do not meet when you come back round to where you started, the square is off the reference face or the stock is not straight, and you have found that out before cutting. Use a marking knife rather than a pencil for anything that must be accurate. A knife line is thinner, it does not smudge, and it gives the saw teeth a groove to start in.

Stand so you can see the top line and the far edge line at the same time, and watch where the blade is leaving the wood rather than where it is entering. The entry point is already cut and cannot change. The exit is where the error is being made right now, so that is the one to watch. This single change of attention fixes most out-of-square cutting and costs nothing. A mirror or a square stood on the work beside the blade helps while you are learning. So does cutting a few practice kerfs in scrap and then checking each one with the square — the feedback is what builds the habit, and three minutes of it beats an hour of being careful.

If the cut has wandered off the line, do not twist the saw. Twisting jams the blade in its own kerf and either binds solid or kinks the blade. Instead, back the saw almost out, tilt it slightly toward the line, and take several light strokes. The teeth on that side will cut a fraction more and the kerf will creep back. It is gradual by nature — a millimetre over several centimetres of cut — and trying to hurry it is what breaks blades. Judge whether it is worth it. If the cut is 2 mm out with 5 mm left to go, it will not recover; stop, and either cut a fresh kerf beside it or accept the piece is oversize and plane or file it to the line afterwards. Deciding early is the whole skill, exactly as with a broken tap.

For anything that must be an exact length, saw a millimetre proud of the line and bring it down to the line with a plane, a file or a shooting board. This is the same argument as sawing before filing, run the other way. A saw is fast and roughly accurate; a plane or file is slow and precisely accurate. Using each for what it is good at is faster overall than trying to make the saw do both. It also removes the pressure from the saw cut, and a relaxed cut is a straighter one. For repeated pieces of the same length, clamp a stop block rather than measuring each one: measuring twenty times produces twenty slightly different lengths, and a stop block produces twenty identical ones.