jointer

A jointer is a powered woodworking machine that flattens one face of a board by passing it over a rotating cutterhead fitted with sharp blades. The machine consists of an infeed table, a cutterhead mounted between two cast iron or steel tables, and an outfeed table, all aligned in a single plane. The operator feeds the board against the direction of blade rotation, and the cutterhead removes a thin shaving in a single pass, typically between 1/32 and 1/16 of an inch per pass depending on machine size and wood species.

Jointers come in several sizes, distinguished by the width of cut they can handle. Common widths are 4 inches, 6 inches, and 8 inches; industrial models reach 12 inches or wider. The cutterhead usually carries three blades arranged symmetrically around the shaft and rotating at 4000 to 6000 rpm depending on the model. A fence can be adjusted to face-joint boards at various angles, though most work is done with the fence perpendicular to the tables for straightedge jointing.

The fundamental purpose of the jointer is to establish a flat reference surface from which all other dimensions in a woodworking project are measured. After jointing one face flat, that face is placed against the table saw fence or jointer fence for subsequent operations. The outfeed table must be set precisely level with the highest point of the cutterhead arc; if it is too low, the board will drop into it after the cut and the surface will not be truly flat.

Common failure modes and setup issues

Blade chatter, visible as waviness across the jointed surface, results from dull blades, loose blade holders, or infeed table misalignment. Snipe, a deeper cut at the beginning or end of the board, occurs when the infeed and outfeed tables are not coplanar. Tearout happens when grain runs uphill into the cutterhead; this is minimized by taking lighter cuts and feeding with the grain direction whenever possible. Regular inspection of blade sharpness and table parallelism prevents most defects.

The jointer is distinct from the planer, which has a single table supporting the wood and two opposing cutterheads; the planer thicknesses boards to a uniform dimension, while the jointer merely flattens a single surface. In a typical milling sequence, a board is jointed on one face, then planed to thickness, then jointed on an edge, then ripped to width. The name derives from the tool's primary use in preparing joints by ensuring that mating surfaces are truly flat.