Plywood Knowledge and Glossary of Terms

Plywood Knowledge and Glossary of Terms

A glossary of industry terms:

Backs: The reverse side to the face of a plywood panel. Generally, the poorer side of any grade plywood panel calling for a face and a back.

Bark Pocket: A small area of bark around which normal wood has grown.

Burl: A swirl or twist in the grain of wood, usually occurring near a knot, but which itself does not contain a knot.

Core: The innermost portion of plywood usually composed of veneer. Also referred to as a “center.” A core may also be made of fiberboard, particleboard or lumber.

Crossbar: An imperfection or irregularity in the grain of wood running at right angles to the length of the board.

Cross banding: Inner ply veneer placed at right angles to the core, face and back of a plywood panel.

Defects: Anything interrupting the smooth flow of a wood surface. This includes loose knots, splits, voids, wormholes, bark pockets and others.

Delamination: The separation of the inner plies in a panel due to the failure of the adhesive bond.

Face: The best side of a plywood panel in which the outer veneers are of different grades.

Grain: The pattern, size and direction of the fibers in wood or veneer.

Gum Spots: Accumulation of resinous material often found on panel surfaces. May be removed by sanding.

Half-Round Slicing: Off-center slicing cut slightly across the annular grown rings resulting in half-round, plain sliced or rotary characteristics.

Hardwood: General term referring to the wood of many different deciduous trees as opposed to the softwood of evergreen or coniferous trees. Does not relate to the density of the wood.

Knot: Circular portion of a board or veneer that was once the base of a branch or twig growing from the trunk of a tree.

Knot (Open): Opening produced when a portion of a know has dropped out or separated due to seasoning.

Knot (Pin): Sound knots less than 1/4″ in diameter.

Knot (Sound): Knots that are solidly fixed by growth and retain their place in lumber or veneer.

Knothole: Opening produced when knots drop from the wood in which they were once embedded.

Lap: The overlapping of one piece of veneer on another in the same layer of ply.

Medium Density Fiberboard (MDF): A panel or core material manufactured from pressure-cooked wood fiber, resin and wax.

Mineral Streak: A discoloration of hardwood and hardwood veneer.

Particleboard: A panel or core material manufactured from pressed sawmill shavings, resin and wax.

Patches: Filler material inserted into defects of veneers or panels for repair.

Plain Sliced: Veneer sliced from a log tangent to the tree’s annual rings.

Ply: A single sheet of veneer forming one layer in a multi-layered piece of plywood.

Plywood, Hardwood: A panel composed of layers of inner plies, or other core material joined with an adhesive to a face veneer of hardwood and a back veneer, usually also composed of hardwood.

Quarter Slicing: Quartered log sliced at right angles to the growth rings.

Rift Cut: Veneer cut from a quartered log on a 90-degree angle to the grain.

Rotary Cut: Veneer peeled from a whole log set in a lathe and turned against a special knife

Sapwood: The light colored, living portion of a tree located between the heartwood and the bark.

Slip Matched: Veneer sheets that are laid side by side to form a whole sheet with a repetitive grain appearance.

Splits: Separations of the wood fiber running parallel to the grain.

Veneer: Peeled or sliced thin sheets of wood used as inner plies or as decorative faces.

 

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