identify lumber defects grades and sizes

lumber defects

most lumber has some defects, these may be natural occurences or an proudct of the manufacturing and season of the wood.

knots

is a portion of branch or limb cut through by a saw, knots that contain decay are known as a unsound knots.

pitch

is a accumulation of resin and occurs in varying quantities in many species of wood, espically softwoods. pitch may be shown up in various shapes on the face or edge of a piece of stock, depending how the resinous was cut by the saw

pockets

they are defined openings between the annual rings usually containing liquid or granulated pitch or bark.

shakes

shakes are lengthwise seperations of wood usually occur between the growth rings.

wane

is bark or other soft wood tissue left on the edge or corner of a piece of lumber

torendo holes

caused by marine borers which attack logs stored in salt water. holes generally range from 1.5mm to 13 mm in diameter.

termite damage

these insects live in the ground and come up to feed on wood. lumber is treated with chemical poisons. necessary that is used close to.

rot

organic substance and must be preserved to prevent premature rot and distegration. fungus will quicly cause decomposition this is a noticable in wood that is placed in contact with moist soil.

creosote

Creosote is black or brownish oil made of distilling coal tar, and is generally applied to wood under pressure at special wood-preserving plants. It is the most important and most generally useful wood preservative for general outdoor service in structural timbers and exceptionally good for marine use. Creosote has the disadvantage of giving off an unpleasant odour and vapour which is harmful to the skin. Also, wood treated with creosote usually cannot be painted satisfactorily and therefore, creosote treatment is unsuitable for finish lumber.

Pentachlorophenol (Pentox) and Copper Napthenate Solutions (Copper II)

The use of petroleum oils fortified with chlorinated phenols as wood preservative became large scale following World War II. These preservatives were first used primarily for surface applications on window sash and millwork that required a clean, non-swelling, and paintable treatment. Pentachlorophenols do not alter the natural colour. They have the advantages of being clean and odorless, and have good paintability, but still require careful handling when being applied. Because of their distinct advantages over creosote, chlorinated phenol treated wood has increased in popularity so that now many types of lumber are being treated this way by the pressure treatment process.

manufacutring defects

1. Roughness in Dressing The lack of a smooth surface is usually due to faulty knives. A nick out of the blade may also cause a raised line to be left on the surface of the lumber. 2. Skip in Dressing The failure of the planer to completely surface the lumber can occur for many reasons, but usually is due to surfacing irregular material. 3. Torn Grain This usually is the result of planing against the grain of the wood which may be difficult to prevent in highly irregular cross grain lumber. 4. Machine Burn This is a "dark burn" line caused by the board jamming in the planer and the subsequent heating up of the cutter knives as they continue to spin. 5. Wire Edge This is a compaction imprint on the surface of the wood caused by the feed roller. This occurs when the knives are set for too "thin" of a cut. 6. Surface Waves This is a series of cup-like waves on the board surface caused by the feed rate through the planer being too fast for the cutter speed. 7. Seasoning Defects When lumber is freshly sawn or green, there is generally more moisture in the wood than there is in the air surrounding it. This moisture must be removed under controlled conditions; otherwise the wood may warp or crack as it dries. Warping or cracking tends to occur when wood dries unevenly

cracking

This is caused by drying too fast.

Twisting

This is common to plywoods and dimensional lumber and is often caused by improper storage.

bowing

This is caused by improper storage or drying.

Crook

This is caused by improper storage or drying. Most dimensional lumber will have a crown. Cabinetmakers/carpenters must be familiar