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| Old growth (virgin timber) |
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Old, naturally established trees often characterized by dense straight grain and a lack of knots and defects.
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| Open center circuit |
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One in which pump delivery flows freely through the system and back to the reservoir in neutral.
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| Open center valve |
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One in which all ports are interconnected and open to each other in the center or neutral position.
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| Open saw |
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An open circular saw is one that is stretched too much in the inner area for the speed at which it is running. It will not stand up straight and will heat in the center while running. In inserted-tooth circular saws, worn shanks can also cause and open saw. Also called a "Dished saw".
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| Oriented strandboard (OSB) |
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Composed of strand-type flakes aligned in directions which make a panel stronger, stiffer, and with improved dimensional properties in the aligned directions than a panel with random flake orientation.
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| Orifice |
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A restriction, the length of which is small in respect to its cross-sectional dimensions.
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| Outfeed |
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The side of a power tool where the board exits.
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| Oven-dry wood |
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Wood dried to a relatively constant weight in a ventilated oven at 102° to 105°C.
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| Ovendry weight |
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Weight obtained by drying wood in an oven at 102 degrees F (plus or minus 3 degrees F) until there is no more weight loss.
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| Overdry |
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Lumber dried to the point of having low moisture content.
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| Overlay |
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A thin layer of paper, plastic, film, metal foil, or other material bonded to one or both faces of panel products, or to lumber, to provide a protective or decorative face, or a base for painting.
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| Overrun |
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The excess lumber, in board feet, actually sawn from logs compared to the amount of lumber predicted by a board foot log scale; usually expressed as a percent of log scale (Scribner).
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| Overs |
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Chips larger than acceptable length or width.
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| Overstorey |
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That portion of the trees, in a forest of more than one storey, forming the upper or uppermost canopy layer.
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