112 



OONVKRSION OF TIMBER WITH THE SAW. 



is preferable to adopt a mixed style of sawing, which will always 

 give a certain proportion of goods showing the silver grain. 



Two very frequently used methods of mixed sawing adopted for 



cutting out planks and boards are those represented in Fig. 57, A 



' and £. A gives pieces of different widths, B pieces mostly of one 



, Fig. 57. 



h\ 



\ 



Ordinary methods of miaeed naming. 



and the same width. The irregular edges of the planks taken off 

 in A and from the side slabs in B can be sawn square with a single 

 cut by placing several planks together one over another. 



When pieces of different scantlinji^s are in demand, it is best to 

 obtain from each log as many of the highest-priced classes as pos- 

 sible. These should, therefore, be traced first of all on the ends of 

 the logs, the remaining space being filled up as completely as possible 

 with traces for inferior scantlings. In this way alone can the 

 largest nioney-return be obtained from a given log and the wast- 

 age in sawing reduced to a minimum. Under the most favourable 

 circumstances the wastage, resulting both from sawdust and from 

 pieces that cannot be utilized, except as firewood, is never less than 

 22 per cent, if there is no objection to sapwood, or 33 per cent, if 

 only heartwood is allowed. When only a single class of thick 

 stuff is demanded, such as railway sleepers, the loss, even in cutting 

 up perfectly sound logs, attains half the volume of the log. 



When pit-saws are used, owing to their great length (8 feet), 

 unless the logs themselves are long, these latter must be supported 

 several feet off the ground across a pair of strong parallel trestles 

 firmly fixed in the ground. With shorter saws it will suffice to 

 raise only one end of the log by resting it on a single trestle, or, 

 if the log is long enough, even across another log laid horizontally. 

 The most convenient support for logs that are not too heavy is the 

 triangular trestle so often used in the plains of Northern India 



