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 lightty 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 hammer; 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 
