190 FELLING AND CONVERSION OF TIMBER. 



gives the most suitable curvature for general work. The 

 Nonpareil saw is the best of the straight saws. 



For practised sawyers, working with a curved saw is less 

 fatiguing and the motion corresponds better with the move- 

 ment of the arms than in using straight saws ; the sawyer can 

 also work in a more upright and less cramped position in the 

 former case. 



With a curved saw there is also more room for the sawdust, 

 and the latter is less hindering to the work owing to the 

 curvature of the saw (Fig. 110). It must, however, be admitted 

 that the use of curved saws requires more skilled and expe- 

 rienced sawyers than that of the straight saw, for the curved 

 saw is more liable to stick when the blade is not always working 



in the same plane, a difficult 

 thing to secure at first. The 

 chief rule is to guide the saw 

 n lightly, and use no unneces- 

 sary force. In the case, 

 therefore, of unskilled saw- 

 yers, such as men only 

 occasionally employed in 



sawing, it is better to re- 

 Fig. HO.-Cutting line of a curved saw. stricfc them t() the ^ Qf 



straight saws. For skilful sawyers, in coniferous forests, the 

 curved saw only should be used. 



As regards the length of saws, there is more risk of the 

 blade bending and buckling (or sticking in the wood), if the 

 saw be too long, while very short saws tire out the sawyers, 

 and cannot be used with large timber. Lengths from 4J to 

 5 feet, with a breadth of 8J inches without the teeth, are the 

 most effective dimensions for a cross-cut saw. 



As regards the thickness of the blade, all saws should 

 become gradually thicker away from the back, but the thick- 

 ness should be only sufficient to prevent too great liability to 

 bend. 



As regards weight, saws should not be too light, or their use 

 becomes very fatiguing, and 5J pounds is the best weight. 



The construction of the teeth is of importance and dog 

 teeth are most effective ; M teeth, however, give good results 



