. Appleton's dictionary of machines, mechanics, engine-work, and engineering. he joiners art, and to theconsideration of which we will now proceed. When the green wood is cut up into planks, boards, and veneers, the splitting which occurs in thetransverse section is less to be feared than distortion or warping, from the unequal contraction of thefibres. Thick planks are partially stayed from splitting and opening, by cleets nailed upon each end;boards are left unprotected, and veneers are protected from accidental violence by slips of cloth gluedupon each end. One plank only in each tree can b
. Appleton's dictionary of machines, mechanics, engine-work, and engineering. he joiners art, and to theconsideration of which we will now proceed. When the green wood is cut up into planks, boards, and veneers, the splitting which occurs in thetransverse section is less to be feared than distortion or warping, from the unequal contraction of thefibres. Thick planks are partially stayed from splitting and opening, by cleets nailed upon each end;boards are left unprotected, and veneers are protected from accidental violence by slips of cloth gluedupon each end. One plank only in each tree can be exactly diametrical, the others are parallel therewith, and, asshown in Fig. 3937, the two sides of all the boards, but that from the centre are differently circum-stanced as regards the arrangement of the fibres, and contract differently. It will be generally foundthat the boards exposed to similar conditions on both sides, become, from the simple effect of drying,convex on the side towards the centre of the tree ; this will be explained by a reference to the diagram. C. «-_-— </ Fig. 3941, which shows that the longest continuous line of fibres is concentric with the axis of the let a, b, c, d, e,f represent the section of a board, the line b e of which is supposed to contain fivefibres, and the arc d bf thirty: therefore, supposing every fibre to shrink alike in general dimensions,the contraction on the arc will be six times that upon the short radial line, and the new margin of theboard will be the dotted line which proceeds from g to h, the departure of which from the originalstraight line will be five times as much at d as at e. 3942.
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Keywords: ., bookcentury1800, booksubjectmechanicalengineering, bookyear1861
