— VDe 



86 TOOLS FOK FKLLING AND CONVKRSlON. 



a kerf, and the teeth get worn away unnecessarily quickly, and the 

 surfaces cut are unnecessarily rough. The strongest setting should 

 not increase the width of the cutting edge to more than double 

 the gauge of the saw. As a rule, ripping saws require very little 

 set, since the two sections, from the wood in the interior being 

 rhoister, bend away outwards and make room for the saw. The set 

 should be uniform throughout the length of the saw, for if one tooth 

 projects sideways beyond the rest, besides that it will become worn 

 much quicker, it will also scratch the wood and produce a rough 



surface. The set should be the 

 Fig. 32. same on both sides, otherwise the 



saw will cut more freely on the side- 

 of the stronger setting and have a 

 -itendency to run towards it. The 

 Indian sawyer sets the teeth of his 

 saw either by blows or by leverage 

 with a hand saw-set (^Fig. 32). 

 The teeth should be set alternately 

 to different sides — a very obvious warning, but one which our saw- 

 yers very often neglect. 



In a bent set each tooth can cut on only one side, and generally 

 the teeth have a tendency to spring in and are more subject to side 

 strains. To obviate these defects the spread set has been devised, 

 in which the points of the teeth are flattened out so as to become 

 broader than the rest of the blade. This kind of setting is perhaps 

 too advanced for introduction into India. 



The Blade. — The gauge of a saw ought to be only just 

 sufficient to give it the requisite stiffness. The disadvantages of 

 a thick-bladed saw are that it requires more set, is in need of 

 more frequent sharpening, is more difficult to file, wastes more 

 wood, and, being heavier and cutting a wider kerf, is more fatigu- 

 ing to use. If the blade is too thin, the saw is liable to twist 

 and make an uneven kerf, the result being buckling. The Indian 

 method of filing the teeth, so that they cut when being drawn 

 towards the operator, permits of the use of much thinner blades 

 than the English method, which makes the saws cut in thrust. 

 Saws are sometimes made thickest along the cutting edge and 

 become gradually thinner towards the back. This is in order to 

 dispense with the necessity of any set at all. 



In order to reduce friction to a minimum, the blade should be 

 as smooth as possible, and its width should be no more than what 

 is required to prevent it from bending in its own plane. The 



