Backsaws: Dovetail, Carcase and Tenon Saws

A backsaw is a short saw with a thin plate and a stiff strip — the back, or spine — folded or fixed along its top edge (see the plate above). The spine holds the plate flat and straight, so the plate can be thinner than an unsupported saw’s and still stay true in the cut. Veritas describes its composite spine as providing the saw’s strength and rigidity.

The spine sets the limit too. The saw cannot cut deeper than the distance from its tooth line to the underside of the spine, so a backsaw is for joints and small parts, not for sawing boards to width. That trade — depth for control — is the whole point of the tool.

• Plate: thin steel carrying the teeth. Published figures include 0.020 in for Lie-Nielsen’s dovetail, carcass and tenon saws and 0.024 in for Veritas’s tenon saws.
• Spine: brass, steel or composite, adding weight and stiffness. The weight helps the saw cut without being pressed down.
• Tooth line: usually fine and lightly set. Lie-Nielsen gives 0.003 in of set per side on its smallest backsaw, for a 0.026 in kerf, and says the narrow kerf helps the saw cut straight.
• Handle: a closed or pistol grip that sets the angle of the push. Veritas shapes its handle so that the index finger rests on the spine, pointing along the saw.

Backsaws come in a range of sizes, and makers group them under three common names. Carcase and carcass are both used; Lie-Nielsen and Veritas both write carcass. The figure draws one maker’s three saws to the same scale, so their differences in length and depth can be compared directly.

Each joint is made of cuts along the grain and across it, and a backsaw is filed for one or the other. The rule is the same as for full-size saws: rip teeth for cuts along the grain, crosscut teeth for cuts across it. Veritas notes that most dovetail cuts are rip cuts, and uses crosscut saws for work such as tenon shoulders.

Tooth count follows the thickness of the stock. A fine-toothed saw in thick wood clogs and cuts slowly; a coarse one in thin wood can tear it and is hard to start. The makers’ own guidance, such as Veritas’s pairing of tooth count with stock thickness, is a sound starting point.

Backsaw joinery depends on the layout. The measuring and marking guide covers the knifed and gauged lines these cuts follow; the guide to cutting straight covers starting and tracking a cut. Two points matter more with a backsaw than anywhere else.

• Saw on the waste side, touching the line. In a joint, half a kerf on the wrong side is a loose fit.
• Give crosscuts a wall to start against. Deepen a knifed shoulder line with a chisel, paring a small V from the waste side. The saw’s teeth drop into the V and the finished shoulder is the knife line itself.

The spine that makes a backsaw accurate also makes it specialised. It limits the depth of cut, so the saw cannot rip a board to width. The thin plate cuts a narrow kerf with little effort, but it will follow a twist in the grip as readily as a line, so the grip stays relaxed and the saw’s weight does the cutting.

For cuts the spine will not allow, use a full-size saw from the handsaw guide. For a thinner plate that cuts on the pull stroke, see the Japanese saw guide, and for curves and waste removal between dovetails, the coping saw guide.