How Saws Cut Wood

Teeth remove chips; the kerf is the wood they remove

Sawing is a Separating process: each tooth removes a small chip, and successive teeth make a slot. The slot's width is the kerf. The space ahead of a tooth, called the gullet, carries chips out of the cut.

Many steel saw teeth have set: teeth bend slightly to alternating sides so the cut is wider than the blade body. Carbide-tipped circular blades commonly get that clearance from tips wider than the steel plate instead. Set and kerf are related, but they are not the same measurement.

This page explains cutting concepts. For operation, use Machine Hazards and Housekeeping and Equipment Operating Procedure.

Rip along the grain; crosscut across the fibers

A rip cut runs along the grain, usually to reduce a board's width. A crosscut runs across the grain, usually to reduce its length. Describe the cut relative to the grain, not just as a long or short cut.

Ripping teeth commonly have a flat, chisel-like cutting edge. Crosscut teeth commonly have alternating bevels that score and sever fibers at the sides of the cut. These are useful patterns, not universal rules: combination and specialty blades use other arrangements.

Why tooth geometry changes the surface

Across the grain, fibers can break beyond the intended cut if they are pushed away before being severed. Beveled teeth help slice those fibers. Along the grain, chip removal is a major concern. A blade's tooth shape, spacing, sharpness and feed all affect the result; tooth count alone does not identify its job.

Balance tooth count, chip space and hook angle

For circular blades of the same diameter, more teeth generally share the work into smaller bites at the same feed and rotational speed. That can improve a crosscut surface, but leaves less space for chips. Thick ripping cuts often benefit from fewer teeth and larger gullets. “Thicker wood needs more teeth” is not a general rule.

Band and reciprocating blades commonly specify teeth per inch (TPI). Tooth spacing must suit the thickness engaged in the cut. A coarse blade has more chip space; a finer blade can suit thinner stock and finer work. Blade width also matters on a band saw: a narrower blade can follow a tighter curve.

Hook angle describes the tooth face's lean relative to a radial line on a circular blade. More positive hook generally gives a more aggressive bite; low or negative hook is less aggressive. Machine type and the blade maker's intended application matter along with the desired finish. A ripping blade is not automatically appropriate on a miter saw.

See Feeds and Speeds for the relationship between tooth engagement, feed and cutting speed; metal-cutting settings do not transfer directly to wood.

Blade terminology reference

Ridge Carbide Tool's saw-blade design glossary defines gullet, kerf and hook angle; its top-grind guide compares tooth shapes. Choose a blade specified for the machine and cutting application.

Count cuts before calculating strip yield

Start with the usable width after any edge preparation. Let W be usable board width, s the required strip width and k the kerf, all in the same units. These ideal layouts assume straight cuts, exact dimensions and no extra finishing allowance.

One cut per strip, leaving an offcut: used width = n(s + k). The maximum whole number is floor(W / (s + k)); “floor” means round down. For a 12 in board, 3 in strips and a 1/8 in kerf, floor(12 / 3.125) = 3 strips. Three cuts use 9.375 in, leaving 2.625 in. Four strips alone use 12 in, leaving no room for the cuts.

All final pieces use both original outside edges: W = ns + (n − 1)k for an exact partition. There are only n − 1 cuts between n pieces. If a layout leaves an extra offcut to separate, count that extra cut too. Draw the layout before choosing a formula.

Real layouts also allow for defects, edge trimming and later machining. Kerf is material removed, not useful strip width.

Practice strip yield Practice cuts between pieces Practice the remaining width