SMALL SAWMILLS, THEIR EQUIPMENT, ETC. 27 



small rings between the saw and the fast collar and the large ring 

 against the loose collar. If the saw heats in the center when the 

 mandrel runs cool in the boxes, cool it off and give it a little more 

 lead into the log. If the saw heats in the rim and not in the center, 

 cool it off and give it a little more lead out of the log. Circular 

 saws, revolving as they do at high speed, have a tendency to stretch 

 on the rim, which causes them to cut out of line, dodge knots, run 

 snaky, and become hot in the rim. 



HAMMERING A SAW BLOCKING. 



To overcome rim expansion, saws are loosened in the body by ham- 

 mering. This operation is called "blocking," and the effect on the 

 saw is called tension. If after long use or through accident a saw 

 will not run true and requires hammering, great care should be exer- 

 cised in bringing it back to proper adjustment. Hammering should 

 hardly ever be done by anyone except an expert. However, if con- 

 siderable care is exercised, a person who is a fair mechanic should 

 attain good results by practice and observation. 



After taking the saw from the mandrel, stand it upright on the 

 floor and examine it carefully on both sides with a straight edge for 

 any inequalities such as lumps. Mark these lumps with chalk on 

 the full or convex side, then place the saw on a block of wood and 

 hammer lightly on the high side. Don't hammer the saw on an 

 anvil, for that will change its tension. 



If struck too heavily, the plate will be dented or the lumps knocked 

 through to the other side. When the lumps are knocked too far it 

 is practically impossible to get them back or to restore the equality 

 of the plate. Lumps are sometimes round, but are usually oblong. 

 To remove round lumps, use a round-faced hammer, which leaves an 

 impression one-half inch in diameter. To remove oblong lumps, use 

 a cross-faced hammer. The blows should follow the direction of 

 the lump. Never use an ordinary carpenter's harmner; it will ruin 

 the plate. Do not be content with putting the straight edge on once 

 or twice and hammering a little. After a few blocks, apply the 

 straight edge again, and continue alternatively applying the straight 

 edge and lightly hammering until all inequalities are removed 



The saw should then be placed on an anvil (not a wooden block) 

 and examined for tension. Raise one side so that the center of the 

 saw just clears the anvil while the opposite side rests on the bench 

 or wooden board, which should be 1 inch below the surface of the 

 anvil. The body of the saw should be loose enough to drop away 

 from a straight edge placed across the log side evenly from rim to 

 rim. If a 36-inch straight edge is used on a 48-inch saw, you should 

 be able to see light between the straight edge and the center. Always 

 try the long side for this drop. If you find there is not sufficient 



