T to Z of sawmill terminology

Glossary T – Z

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A board that becomes gradually smaller toward one end.

Tension in logs is caused by a number of factors, including climate, sun exposure, growth rate and species of the tree. Logs with high tension must be milled carefully to avoid bowing and potential wastage of the lumber.

A term often used interchangeably with grain. Sometimes used to combine the concepts of density and degree of contrast between earlywood and latewood, or generally the relative size and arrangement of the wood cells.

Thousand board feet
Unit of measurement equal to 1,000 feet of wood having a thickness of 1” by 12” by 12”.

(1) General term applied to forests and their products. (2) Sawed lumber more than 4 by 4 inches in breadth and thickness.

A quality of wood that permits the material to absorb a relatively large amount of energy, withstand repeated shocks, and undergo considerable deformation before breaking.

Tree length
Entire tree, excluding the unmerchantable top and limbs.

Tungsten is a multi-purpose metal, and when used as an alloying element it increases the strength of steel at normal and elevated temperatures. Tips come in various grades, depending on the application.



Variable costs
Operation costs that result from running a machine, calculated on an hourly basis; includes cost of labor and items such as fuel, oil, wire rope, and replacement parts. Also known as operating costs.


Bark or lack of wood on the edge or corner of a piece of wood, resulting from the piece being sawn from near the outer circumference of a sawlog.

Any variation from a true or plane surface. Warp includes bow, crook, cup, and twist, or any combination thereof.

A long thin board with one edge thicker than the other; used as siding by lapping one board over the board below.

The mechanical or chemical disintegration and discolouration of the surface of wood caused by exposure to light, the action of dust and sand carried by winds, and the alternate shrinking and swelling of the surface fibres with the continual variation in moisture content brought by changes in the weather. Weathering does not include decay.

To clear or separate a board as it is being cut, with wooden or plastic wedges. This helps to carry the weight of the board, especially when cutting slabs.

Tree or trees that have been uprooted or broken off by the wind. Also known as blow down.



The proportion of the log converted into lumber is the product that produces the greatest value. The percentage of the log that winds up in as lumber (54-55%), sawdust (4-19%, or chips (27-41%) depends upon thickness of lumber being cut, skill of the sawyer, type of headsaw, saw kerf, losses in edging, trimming, drying, and surfacing.


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