Chapter 7 Flashcards
develop due to anisotropic and hygroscopic nature of wood and are associated mainly with changes in moisture content of wood below fiber saturation point.
Seasoning or Drying defects
two types, end checks and surface checks
checks
more extensive than checks
splilts
any distortion from the true plane of wood that occur due to differential shrinkage (anisotropy)
warping
Types of warping
- bow - twist - diamond
- crook - cup - oval
irregular depression and elevation on wood surface due to effect of excessive shrinkage
collapse
presence of residual drying stresses brought about by tension in the wood core and/or compression in the shell
casehardening
caused by too high kiln temperature and improper steaming, also called hollow horning, results to intensive internal checks and splits
honeycombing
similar to shake on standing trees
ring failures
occur on wood surrounding the pith during the initial stage of drying where there is too high initial temperature
box-heart splits
What are the machining defects
Raised Grain
Loosened Grain
Fuzzy Grain
Chipped and Torn Grain
the roughened condition of the surface of dressed lumber in which the hard summerwood is raised above the softer springwood, but not
torn from it.
Raised Grain
This is attributed to lumber that are machined at MC greater than 12% and is increased by dull planer knives.
Raised Grain
The wood surface is described as having a corrugated feel and appearance.
Raised Grain
separation and curling of the tips of growth rings on the surface of flat-grained lumber.
Loosened Grain
This causes curling of the loosened splinters when individual growth increments
are freed by sanding or planing.
Loosened Grain
occurs when wood fibers become loosened on the surface of a board in large numbers. Wood cells that swell under the action of swelling agents, such as stains, or as a result of atmospheric humidity, maybe injured in the process of planing or sanding
Fuzzy Grain
This may also be affected by the rate of feed of stock to machines with feeders and the slope or variation of the grain of the wood. Lumber with a surface MC of 5% or less is more prone
Chipped and torn grain
Chipping may be minimized by
reversing the direction of the travel of the board through the planer.
any abnormality that may lower its strength and durability and limit its utility.
Log defect
two main categories of log defect
(a) those that reduce the volume of sound wood and/or lower its durability, and
(b) those that lower its strength and/or limit its utility.
refers to such defects as knots, stains, holes, bark pockets and related defects usually included in the end-products of the logs, either in the form of rough lumber or lumber products.
A defect that lower its strength and/or limit its utility
indicated by abnormal brittleness, torn grain, low density and reltively light color in the central portion of the heartwood.
Brash Center
This is very common in most PMG species. It commonly occurs near or at the center of the logs, particularly the butt logs.
Brash Center
This defect may cause lumber to break abruptly across the grain when roughly handled.
Brash Center
This defect occurs in a log cut just at the base of a fork in which two
separate pith centers appear and are often separated by a bark pocket.
Double Pith
Sawn lumber from this defect is usually cross-grained and is likely to split near the bark pocket area.
Double Pith
These are round or irregular channels of varying lengths, and the diameter varies from 3/8 to 1 inch caused by wood consuming grubs that hatch eggs, laid in the bark of standing trees or recently felled trees working their way inside the wood to the surface
Grub Channels
A loose heart is the tangential separation of fibers completely around
a growth ring within the heart or core of the log.
Loose Heart
confined to the heart center, while a ring shake develops anywhere between the pith and bark.
Loose heart
a tangential separation of the wood fibers along the parts of the growth ring. It may be found at the center and sometimes through the wood.
Ring Shake
Lumber with _________ depending in size, may seriously weaken the resistance
of wooden members to longitudinal shear.
Shakes
This refers to a log in which the pith is outside the geometrical center of the log. Posing some problems in manufacturing, it indicates the presence of tension wood and shrinks excessively. not used for veenering
Off-center Pith
These are tiny round holes, made by ambrosia beetles, roughly less than 1/16-inch in diameter.
Pinholes
small wood-boring insects which attack newly cut timber, causing what is commonly called “pinhole” defect.
Ambrosia Beetle
As its name implies, it is a defect found in butt logs. Usually, in Philippine dipterocarps, the rot starts right from the butt end up to the top or small end of the log.
Butt Rot
– This is usually confined to the center of the log and affects its entire length. However, rot which results from wounds or rotten knots is usually found in the outer rim of the wood.
Center Rot
This is sometimes called spider heart. It is a multiple radial separation of the wood fibers, starting from the pith center and extending out to at least three directions.
Heart Checks
appear in lumber as short cracks or seams, sometimes filled with resin, and affecting the whole face of the board.
Heart Checks
This is a single, radial split that extends to both sides of the pith. In some instances, it is restricted to the heart center of a log and, in others, it progressively enlarges with heartwood formation and then extends across the heartwood zone.
Wind Shake
Log Surface Abnormalities
Bumps
Burl
Cat Face
Knots
Splits
Stains
Sweep and Crook
Wormy and Unsound Sap
Wounds
a protuberance on the log which is overgrown with bark. may be abrupt or only a gradual undulation that tapers back in all directions to the the normal contour of the log.
Bumps
a protruberance on the log which is sound, hrad and round or horizontally ridged without protruding limbs, twigs or stubs.
Burl
causes the grain in the wood to be distorted, exhibiting a wavy, curly, or bird’s-eye effect.
Burl
a scar found in on the surface of a log, and it may be fikked with wood and bark. This results from the wounding of a tree by falling trees, wind storms or lightning. (4) Knots – Knots are defined
Cat Face
cuts or broken-off limbs or sprout branches, green or dead, protruding, flush, or depressed in which the exposed wood may be sound or rotten.
Knots
a longitudinal separation of wood fibers, extending deeply into the log.
Split
generally caused by accidents during operations. At times it is due to the release of internal stresses when the tree is cut.
Split
a lengthwise separation of the wood, which extends from one surface to the opposite or
adjoining side.
Split
These are abnormal discolorations of wither black, blue, brown or olive-green, usually in variegated or streaky patches.
Mineral streaks and stains
This is characterized by tangential bands or rings of dark reddish-brown in the sapwood zone. These bands appear as if normal of
normal heartwood and are believed to be due to injury in the sapwood region. These are closely associated with mineral stains in the same log.
Pathological heartwood
is defined as the amount of deviation of a log from a straight line drawn from one end to the other end of a log, over and above the amount of taper.
Sweep
the abrupt bending or curving of a certain portion of the log.
Crook
occurs when there are two of these curves or bends along the log.
Double crook
When the sapwood of a log has been attacked by grub worms, this log is called
wormy.
the sapwood are commonly caused by blue stains. Stains, caused by fungi, are almost invariably sapstains, although heartwood may be affected, in which case, incipient decay is indicated.
Unsound sap
openings in the bark that expose the sapwood and sometimes the heartwood portion.
Wounds
Shallow depressions on indentations in the surface of a board caused by shavings or chips getting imbedded in the surface during the process of dressing. They may be formed by a planer or jointer.
CHIP MARK.
rather than running parallel to the long edge of a board, for example, the grain runs at an angle to it. Such wood is not permitted for structural applications in the American Forestry Association guidelines because it lacks the same structural strength as an equal-sized piece that has the grain running parallel to the edge.
DIAGONAL GRAIN.
An irregularity in the surface of a board where wood fibers below the level of the dressed surface have been torn or broken out by a planer.
TORN GRAIN.
more commonly associated with rough milled lumber. In the case of construction lumber (e.g., 2x4s), it can be bark or missing wood.
WANR
A darkening of the wood due to overheating by machine knives or rolls when pieces are stopped in the machine.
MACHINE BURN
A depressed cut of the machine knives at the end of the piece.
MACHINE BITE
A groove cut by the machine below the desired line.
MACHINE GOUGE
the process of converting raw timber to forms suitable for woodworking or
construction projects.
CONVERSION
WOOD DEFECTS FROM CONVERSION
1.1.CHIP MARK.
1.2.DIAGONAL GRAIN.
1.3.TORN GRAIN.
1.4.WANE.
1.5.MACHINE BURN.
1.6. MACHINE BITE.
1.7.MACHINE GOUGE.
the process of drying lumber (either in a kiln or air drying) to an appropriate level of moisture for woodworking and other commercial uses.
Seasoning
a nonspecific term that refers to a distorted or misshapen board.
WARP
A curvature formed in the direction of the length of timber. A bowed board is flat, but bent, like a road going over a hill.
BOWING.
Where the board curves in length and width like a propeller.
TWISTING.
Where the face of a board warps up across its width such that if one looks at the end of the board, it will look like a shallow letter “U.” Is common with plain-sawn lumber.
CUPPING.
Occurs when the board remains flat in width, but curves in length like a river going around a bend.
SPRING.
is among the worst of drying defects because it’s irreversible and usually cannot be detected by looking at the face of the lumber.
HONEYCOMBING.
internal stresses cause various radial and circular cracks to develop in the interior portion of the wood
HONEYCOMBING.
NATURAL WOOD DEFECTS
BARK POCKETS.
BIRD PECKS.
BURLS.
COARSE GRAIN.
RAISED GRAIN.
SHAKE.
KNOTS.
STAINS.
SPALTING.
TWISTED FIBERS.
Formed when a small piece of the bark protrudes into the lumber. This area is generally considered unsound.
BARK POCKETS.
Caused by birds, especially woodpeckers, which peck on trees when trying to feed on the insects living in or under the bark and in the wood of the tree.
BIRD PECKS.
If the tree grows rapidly, the annual rings are widened. It is known as coarse-grain timber and possesses less strength and durability.
COARSE GRAIN.
Anything that gives the wood a corrugated feel. Typically, this is caused by the harder summerwood rising above the softer springwood in the growth ring. The growth rings do not separate.
RAISED GRAIN.
A group of splits radiating from the pith or
center of the tree in the form of a star. It is wider on the outside ends and narrower on the inside ends.
Star Shake
KNOTS. The base of the branches forms a mark on the stem as new branches grow, resulting in dark-coloured stains on the surface. These dark-coloured rings are due to the continuity of wood fibres and they are known as
Knots
A knot usually lighter in color and generally never fall out
LIVE KNOT
A knot darker in color and may fall off leaving a hole that can weaken the strength of the limber
DEAD KNOT
A knot that is not inter-grown with the
surrounding wood.
ENCASED KNOTS
A hole left where the knot has been knocked out.
KNOTHOLE
Limbs that have been cut across or cut lengthwise, showing the end grain or length section of the limb or knot. These knots generally have splits and severe grain deviations near them.
SPIKE KNOTS
Any form of wood discoloration caused by fungi. It’s typically found in dead trees, so if the wood isn’t stabilized at the right time it will eventually become rotten wood.
SPALTING
Types of spalting
Pigmentation
White rot
Zone lines
These are known as wandering hearts and are caused by the twisting of young trees by fast-blowing wind.
TWISTED FIBERS.
caused by a fungus that feeds on the sap. It does not live in live trees due to lack of oxygen. The color does not degrade the cellular structure and does not count against wood in the grading process.
BLUE STAIN
A form of wood decay found only in softwoods that destroys the wood’s cellulose, eventually causing cracks across the
grain.
BROWN ROT
After the wood that was once infected with brown rot dries out, the cell walls of the remaining wood begins to break down and can be crushed to a dry powder.
DRY ROT
This is formed when a branch has come out of the tree. The heart wood is exposed to an attack from insects and the elements. Ultimately, the tree becomes weak and it gives a hollow sound when struck with a hammer.
HEART ROT
occurs when the fungus digests the lignin and cellulose therefore stripping out the darker colours with it. This gives the timber a soft spongy feel when touched.
WHITE ROT
Insect defects
Wood boring beetles
Pin-hole borers
Marine borers
In softwoods, the type of reaction wood formed is called ______ ___ while in hardwood, it is called _______ ____
compression wood, tension wood
