A-A-52301
Materials:
Wood drawing boards. Wood shall be seasoned or kiln dried to assure dimensional stability and permanent configuration. Cross grain (slope of grain) whether on the face or edges of a piece shall be not more than 1 inch in length of 10 inches. Wood shall be free from decay, splits, checks, shakes, bark, pitch pockets, holes, and knots. Plywood or veneer shall be free of blemishes that would impair the working surfaces of the boards.
Composition core drawing boards. The composition core board shall be plastic-filled with the core having a density of not less than 30 pounds per cubic foot and a urea formaldehyde resin content of not less than 7 percent, or a commercially proven equivalent. Working surfaces shall be not less than .0625-inch thick. Multiple plies of wood used for strength shall be laminated in cross-grain patterns of continuous wood, and sanded smooth on each side.
Edge banding. Edge banding of core boards shall be basswood, pecan, maple, oak, birch, white pine or ponderosa pine, and shall be applied to all exposed edges. Metal channel molding mounted flush with the working surfaces for parallel end guides and cross sectional support shall be acceptable. When mounting strips are laminated into core boards, strip areas shall be plainly marked on the edges of the board.
Steel. Wood screws, bolts, washers, and hardware moldings, chains etc., shall be of commercial grade corrosion-resisting steel or shall be made corrosion-resistant by commercial standards.
Wood trestles: Wood used in trestles shall be seasoned or kiln dried to ensure lamination integrity and dimensional stability. Wood shall be oak, maple, or dense hardwood variety with cross graining not more than 1 inch in 20 linear inches, and free of decay, splits, checks, shakes, bark, pitch pockets, holes, and knots. Trestles shall be unassembled. Trestle components shall be placed in a cushioned box to prevent movement and damage of the trestle components.
Construction. Wood boards shall be made from the same species of wood for the entire working surface of one drawing board. The working surface shall be composed of continuous wood lengths, 1.75 to 5 inches each uniform in width, extending the entire length of the working surface with grain running full length whenever practical. The laminated body of the board shall be made up of full length pieces bonded together with waterproof resin adhesive. Bonded joints, full set, shall have a strength greater than the wood being bonded. Drawing boards more than 45 inches in width and 85 inches in length made from laminates of wood, uniform in length, shall be reinforced across the grain with three battens not less than 1.0625 inch x 2 inches in cross sectional dimensions, standing perpendicular to the board and secured with
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