PATTERN MAKING 



In addition to these sizes there should be a moderate amount of 

 1-inch resawed and dressed to inch or to -fo inch; and the same 

 amount of l^-inch resawed and dressed to \ inch. The two last 

 thicknesses are used for gluing and building up the rims of pulleys, 

 gear wheels, and other light work where strength and durability 

 are required. 



Warping and Twisting of Wood. Observation shows that 

 if one side of a board is kept damp and the other dried, the former 

 will expand so that the plank, although originally straight, becomes 

 curved as in Fig. 1. Or if one side of a board is exposed to the air, 

 while the other is more or less protected, as in the stack of boards 

 shown in Fig. 2, the exposed side of the upper board will give off 

 its moisture more rapidly than the other side, and the board will 

 warp or bend in the direction shown by the dotted lines. The 

 second board will also "draw" and to some extent follow the first, 

 being in turn followed by the third, and so on until the entire stack 

 is warped and bent. 



Fig. 1. 



Fig. 2. 



The same will be found true of a well-seasoned board if after 

 being planed it is allowed to lie on its side on the work-bench. 

 The upper side will give off its moisture more freely than is 

 possible for the under side; the latter being protected and having 

 its moisture retained by the bench. The lower side of the board is 

 thus caused to expand, and the upper to contract, with the result 

 that the board, although originally planed straight, becomes curved. 

 For this reason all lumber, even if well-seasoned, should be so 

 placed in racks, or on end, that the air may have free access to 

 both sides of the planks; and newly planed boards, however dry 

 and well seasoned, should never be stacked together, but so placed 

 that both sides will be exposed alike. 



This tendency to warp is explained to some extent by the 

 porous nature of all woods, and their inclination to give off or to 



