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| Dado |
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A groove cut into one piece to accommodate another piece. A dado is three-sided and cut into a board, usually across the grain, as opposed to a rabbet, which has two sides and is at the edge of the board.
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| Dangling head |
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A type of harvesting head, usually used on a CTL harvester, with a wrist-like action and attachment to the harvester boom. Also called a "single-grip harvesting head" and can rotate in all three axes.
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| DBH |
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See Diameter at breast height.
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| De-superheater |
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A device for removing the excess heat in steam as its pressure is reduced.
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| De-vent |
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To close the vent connection of a pressure control valve permitting the valve to function at its adjusted pressure setting.
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| Deadband |
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The region or band of no response where an error signal will not cause a corresponding actuation of the controlled variable.
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| Deadpile |
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Stack lumber in units without stickers.
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| Debark |
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To remove bark from trees or logs.
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| Debarker |
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Machine which removes bark from a log.
View: Debarker Examples
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| Decay |
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The decomposition of wood substance caused by the action of wood- destroying fungi, resulting in softening, loss of strength, weight, and often in change of texture and color.
View: Decay
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| Decay, brown rot |
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Wood decay in which the attack concentrates on the cellulose and associated carbohydrates rather than on the lignin, producing a light to dark brown pliable residue. Sometimes referred to as "Dry rot".
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| Decay, heart rot |
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Any rot characteristically confined to the heartwood originating in the living tree.
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| Decay, incipient |
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The early stage of decay that has not proceeded far enough to soften or otherwise apparently impair the hardness of the wood. It is usually accompanied by a slight discoloration or bleaching of wood.
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| Decay, white-rot |
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Decay attacking both the cellulose and the lignin, producing a generally whitish residue that may be spongy or stringy.
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| Deciduous |
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A type of tree with broad leaves that usually are shed annually, such as aspen. Commonly referred to as Hardwood.
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| Deck |
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A stack of trees or logs.
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| Decompression |
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The slow release of confined fluid to gradually reduce pressure on the fluid.
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| Defect |
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A characteristic of a tree, log, lumber, or other product that makes it either less desirable or completely unsuitable for the intended purpose. Examples are knots, decay, insect holes, and diagonal grain.
View: Knot Defects, Manufacturing Defects, Natural Defects, Seasoning Defects
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| Degrade |
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Drop in lumber grade due to manufacturing or drying practices.
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| Dehumidifier kiln |
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A kiln working on the heat pump principle. Moisture evaporated from the timber by a flow of warm air is condensed on the evaporator coils of a refrigeration unit and drained away. The refrigerant is compressed and passed through condenser coils, re-heating the air stream.
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| Delamination |
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The separation of the layers of laminated wood or plywood at the glueline, usually caused by moisture, mismanufacture, or defective glue.
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| Delimber |
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Landing-based piece of equipment used to limb trees brought in unlimbed, usually cut with full tree length harvesters. May be of the stroke delimber type or pull-through delimber model.
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| Delivery |
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The volume of fluid discharged by a pump in a given time, usually expressed in gallons per minute (gpm).
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| Delta |
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The amount of change in a number, size or position.
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| Dense |
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A reference to the specific gravity of wood. Lumber classified as "dense" has six or more annual rings per inch, plus one-third or more summerwood, measured at either end. Pieces averaging less than six rings per inch also qualify if the rings average one-half or more summerwood.
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| Density |
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As usually applied to wood of normal cellular form, density is the mass of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex having unit volume. It is variously expressed as pounds per cubic foot, kilograms per cubic metre, or grams per cubic centimetre at a specified moisture content.
View: Metric / Imperial Conversion
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| Diameter at breast height (dbh) |
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Breast height of a tree is considered to be four and one-half feet above ground level.
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| Diameter inside bark (dib) |
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A measurement used in log scaling.
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| Die (swage) |
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One of a pair of shaping tools, which, when moved toward each other, produce a certain desired form in an object. In a swage tool the die is the movable part of the shaper, the anvil the fixed part.
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| Differential current |
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The algebraic summation of the current in the torque motor; measured in MA (milliamperes).
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| Differential cylinder |
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Any cylinder in which the two opposed piston areas are not equal.
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| Diffusion |
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Movement of moisture from areas of high to low concentration or temperature.
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| Dimension lumber |
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Lumber that is sold in a nominal dimension. For example, a 2x4 is dimension lumber with an actual finished size of 1.5” thick by 3.5” wide.
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| Dimensional lumber |
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Refers to the wood used in constructing the wall, floor and roof framing of a platform frame (2x4) house. Dimensional lumber is manufactured in a variety of sizes for use in wall framing, flooring systems, and roof trusses, as well as for exterior applications.
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| Directional valve |
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A valve which selectively directs or prevents fluid flow to desired channels.
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| Dish |
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Used to describe the shape of a "dished" or open saw – one that does not stand up straight, because it has been stretched too much in the inner area for the speed at which it is run. Hence, it assumes a dish shape.
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| Displacement |
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The quantity of fluid which can pass through a pump, motor or cylinder in a single revolution or stroke.
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| Dissolving pulp |
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A special grade of chemical pulp, usually made from wood or cotton linters, for use in the manufacture of regenerated cellulose (viscose rayon and cellophane) or cellulose derivatives such as acetate, nitrate, and others.
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| Dither |
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A low amplitude, relatively high frequency periodic electrical signal, sometimes superimposed on the servo valve input to improve system resolution. Dither is expressed by the dither frequency (Hz) and the peak-to-peak dither current amplitude (ma).
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| Doming head |
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Equipment used to form a dome (chamfer) on the end of roundwood posts. Consists of a rotating cutterhead. Also called capping.
View: Doming Head / Domer Examples
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| Door carrier |
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A device that lifts dry kiln doors and moves them away from the kiln opening along an overhead track.
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| Doors, access |
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Small doors, usually located at ground level, which permit operator access to and escape from the dry kiln interior.
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| Doors, kiln |
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Large openings through which lumber passes when loading a kiln.
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| Double acting cylinder |
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A cylinder in which fluid force can be applied to the movable element in either direction.
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| Double sheave |
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A pulley block with two grooved wheels.
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| Dowel mill |
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Equipment used to process roundwood to an exact diameter the entire length. Also called a rounding machine.
View: Dowel Mill Examples
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| Doweled products |
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Roundwood with a tenon on the end to fit in a hole. Equipment used to create the tenon is called a tenoner.
View: Tenoner Examples
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| Doweled rail fencing |
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A fencing system using rails with tenons on the ends of the rails which fit into a corresponding hole in a fence post.
View: Drill and Tenoner Examples
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| Doweled wood |
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Roundwood turned to an exact diameter the entire length. Equipment used for this process are often called rounding machines or dowelers.
View: Dowel Mill Examples
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| Doyle Log Rule |
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The Doyle Log Rule, developed around 1825, is based on a mathematical formula and is widely used throughout the southern United States. This rule allows for a saw kerf of 5/16 inch and a slabbing allowance of 4 inches, which is about twice the normal amount. Because of this, the Doyle Rule is somewhat inconsistent; it underestimates small logs and overestimates large logs. As a seller of timber, you must be aware that for smaller logs the Doyle Rule will underestimate the actual volume of wood that you have in your trees. (Also see Scribner and International Rule.)
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| Drain |
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A passage in, or a line from, a hydraulic component which returns leakage fluid independently to reservoir or to a vented manifold.
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| Dressed lumber |
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Lumber that has been trimmed and planed at the sawmill.
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| Dressed size |
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The dimensions of lumber after being surfaced with a planing machine. A 2- by 4-inch stud, for example, actually measures about 1-1/2 by 3-1/2 inches.
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| Drive pulley |
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The first of a train of wheels, giving motion to the rest.
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| Dry |
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Seasoned, usually to a moisture content of less than 19%.
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| Dry kiln |
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A chamber in which lumber is dried by controlling the moisture, temperature and air circulation.
View: Dry Kiln Examples
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| Dry lumber |
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As applied to softwoods, lumber sold as "dry" or "kiln dried" is at 19% or lower moisture content, as specified by the American Softwood Lumber Standards. Hardwoods are generally considered dry when at 10% or lower moisture content, although there is no definitive standard as with softwood species.
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| Dry rot |
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A term loosely applied to any dry, crumbly rot but especially to that which, when in advanced stage, permits the wood to be crushed easily to dry powder.
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| Dry weight |
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The oven-dry weight, or simply dry weight, is the weight of wood after drying to a constant weight at a temperature slightly above the boiling point of water (215° to 220°F).
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| Drybulb |
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A sensing device (thermometer) that measures the temperature of the air.
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| Drying defect |
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A feature developing during drying which may decrease the value of a piece of timber.
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| Drying schedule |
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A sequence of kiln conditions which result in a gradual decrease in moisture content of the wood.
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