HackSpace_-_April_2020

LENS

A knot in a boardA knot in a board

is the beginningis the beginning

of a branchof a branch

Left

Cross-section of

softwood board.

Growth rings are

distinct. Diagonal

growth pattern is

rift cut, between

plain-sawn and

quarter-sawn

Left

Cross-section of

plain-sawn log

with boards sawn

tangentially to

growth rings. This

is how most lumber

is cut. Plain-sawing

introduces the most

movement and

warping in boards

boards are made by slicing parallel cuts through the

log. Plain-sawn boards can warp because of their

grain orientation.

A more involved way of cutting a log is to slice it up

quarter-sawn. Quarter-sawn cuts don’t warp because

they are cut perpendicular to the log.

The cross-sections of a log show circular growth

rings, the lines indicate plain-sawn or quarter-sawn

cuts. Plain-sawn boards are cut tangentially to growth

rings. Quarter-sawn boards are perpendicular to rings.

With quarter-sawing, horizontal expansion and

contraction in boards is eliminated.

WOOD DEFECTS

Defects in wood detract from its appearance and

strength. Good grades of lumber have few defects. A

knot in a board is the beginning of a branch. In the

furniture industry, wood with knots is used in hidden

furniture parts, unless a rustic aesthetic is desired.

SELECTING WOOD

Oak is open-grain and rough; maple is closed-grain and

smooth. Maple, birch, and poplar are white; padauk is

red; ebony is black. Some woods fade (such as

walnut), and some darken over time (such as cherry).

Consider this when choosing boards for a project.

Softwoods are used in construction and in the DIY

market. Hardwoods are used in cabinetry and

furniture. Hardwoods are more expensive than

softwoods and sold as rough lumber. Purchase boards

from a small supplier where they can be examined.

Bring a tape-measure to check dimensions, and ask

the supplier if they can cut your lumber to size.

MOISTURE CONTENT

When a tree is cut, it’s high in moisture. After

processing, the wood dries. Wood eventually reaches

equilibrium with its environment (or equilibrium

moisture content, EMC). The EMC of wood in a heated

room is 10 percent. Freshly cut logs can reach 100

percent EMC. When moisture evaporates to within

Above
A knot from a cut
branch in a log