. Canadian forest industries 1910. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. Fif. 7. Battens Acroas Grain Ztg. 8. Grooves as a Precaution Tig. 9. Clips Sliding in Batter Still another method might have been adopted and the section sawn into planks and dried. Then it would present the appearance of fig. 5. The centre plank containing the heart has not appreciably changed its form, but the pieces of each side of it have warped their edges away from the centre plank. What is the reason or law for the changes of form in these various examples ? Th
. Canadian forest industries 1910. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. Fif. 7. Battens Acroas Grain Ztg. 8. Grooves as a Precaution Tig. 9. Clips Sliding in Batter Still another method might have been adopted and the section sawn into planks and dried. Then it would present the appearance of fig. 5. The centre plank containing the heart has not appreciably changed its form, but the pieces of each side of it have warped their edges away from the centre plank. What is the reason or law for the changes of form in these various examples ? They are all due to the simple fact that the shrinkage across the grain is much greater in the direction of the lines aa in fig. 6, than from the heart to the bark b Or, to put it in scientific phraseology, the tangential shrinkage aa is from three to five times greater than the radial shrinkage b. If this fact be understood, the behavior of the various pieces already illustrated can be readily explained. It will also be recognized that the only piece in fig. 5 which has not warped is a true radial piece, or, as a woodworker would say, is a "quartered" board. Quartering is, of course, chiefly practiced to dis- play the silver grain or medullary rays of certain woods. But a quar-. Tig. 10. Bitten Rabbeted (or Buttons Tig. 11. Dovetailed Key Tig. 11. Error In TonnUnt tered board is better than a "slash-cut" one, because it does not warp —at all events, not so naturally and readily as the other. Various mechanical methods for preventing the warping of thin. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Don Mills, Ont. : Southam Business Publications
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