WORKED BY STEAM. 689 



to running double cdgers and trimming saws, trimming off the rough 

 edges and bad ends of the himber.* — Tr.] 



iii. Double-edging circular saws for edging planks and boards 

 consist of two saws on the same axis, the distance between them 

 being capable of adjustment. They feed by rollers. 



iv. Saws for laths resemble the above, but there are 3 to 5 

 blades on the same axis, which cut up planks into laths or other 

 scantling. 



v. Ordinary circular saws, used for sawing planks into thin 

 boards, such as those used for cigar-boxes, packing-cases, staves, 

 &c. The wood may either be pushed by hand along a bench to 

 the saw, or automatic feed may be adopted. 



vi. Another form of circular saw is used for shortening logs, 

 removing bad ends of planks, refuse wood, &c. These saws may 

 be either fixed or portable. I" 



3. Band-Saws. 



A band-sav.- is a long thin flexible steel ribbon uniting to form 

 a belt and bearing teeth on one side. It passes above and below 

 over two large pulleys, the lower pulley driving the saw, while 

 the upper one is driven by it. Thus, like the circular saw, the 

 band-saw cuts continually, and also either vertically or hori- 

 zontally. 



Band-saws require 25 to 40/^ less motive power than circular 

 saws, the friction caused is also less and very little waste of 

 Avood is caused, saving 20% compared with other saws. They 

 yield smooth and fine scantling. 



Band-saws were first used in small work, either with a fixed 

 or moveable table, and especially for cutting along curved 

 lines. More recently they have been used for sawing large butts 

 (fig. 308) and are now ousting frame-saws for this and other 

 purposes, especially in America, where the band-saw is con- 

 sidered the saw of the future and can turn out 40,000 feet in a 

 day. 



Machine-saws for felling trees have been already described 

 (p. 205). 



■' Encyc. Brit., 1886, vol. xxi., p. 345. 



+ For a good descriptiou of an American saw-mill, vide Encyc. Brit., vol. xxi. 



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