Flat sawing

Flat sawing, flitch sawing or plain sawing is a woodworking process that produces flat-cut or plain-cut boards of lumber.^[1]

Lumber produced by flat sawing from a log. Plank A has been cut from the middle, and is as wide as the original log. Plank B has been cut closer to the side, and shows slash grain.

Process

After an initial cut through the diameter of a log, parallel cuts produce flitches: strips of lumber with consistent thickness.^[2] Two cuts on each flitch trim the bark from the sides, and reduces it to a standard board width with squared edges. Two more cuts at each end set the length.

Lumber can be quickly flat-cut with a side-by-side set of mechanical saws.^[3] A slower but sturdier method involves passing the log back and forth over a single saw.

To reduce buckling that may occur along the middle of flat-cut boards, the initial cut may be offset from the diameter, and resulting sections cut further before cutting the flitches.

Comparison

Flat-sawn wood often exhibits "flat-" or "slash grain", where the angle between the visible growth rings and the width of the board is 45° or less.^[4] This makes the wood vulnerable to deformation as it dries, or if later exposed to moisture. Flat-sawn wood is less stable than quarter sawn or rift sawn wood, but can be produced more quickly and at lower cost.^[5]

The face of the board may show curved grain, sometimes with intricate patterns.