in shallow water so that the water pressure is not too great, a short length of pipe may be sufficient to carry the exhaust up
above the cutting plane to enable the worker to watch the cut.
165. Servicing
a. Lubrication. Proper and sufficient lubrication is most important in obtaining maximum performance from the chain
saw. A chain should never be permitted to run dry. Keep the oil reservoir filled with OE, engine oil. The oil fill plug is in
the drive housing, painted blue or red. In extremely cold weather, or to cut wood which contains a considerable amount of
pitch, mix kerosene with the oil. Brush the chain itself with OE, engine oil. Before installing a chain into the chain guide,
apply a thin film of graphite into the guide groove.
b. Adjusting Chain Tension. Chain tension is very important for ease of operation and long chain life. A chain that is
too loose may jump out of the chain guide and bind, causing the motor to stall. A tight chain places a load on the motor
and undue strain on the chain. When properly adjusted, it should be possible to grasp the chain and lift it approximately
l/2-inch above the groove near the center of the guide. The chain may be loosened by turning the idler handle to the left
after lifting the small locking knob above it to unlock the idler handle. To tighten the chain turn the idler handle to the right.
c. Sharpening the Chain. All chain cutting teeth should be sharpened at the same time, because it is important that
all teeth be of equal height. The height of chain teeth should be checked with a straight edge while filing or grinding
procedure goes on. It is possible to file saw teeth to one-fourth of their original height without impairing saw cutting ability.
If sharpening is to be done by hand, a mill bastard file 8-inches long and with round edges should be used. Do not try to
take off too much metal at one time. Long even strokes in one direction, taking care not to rock the file while it is cutting,
should result in a well controlled sharpening job. Care must be given in maintaining equal tooth height and also in
maintaining the clearance between the height of the cutter and raker. Normally, this distance should be 1/32 inch;
however, the difference in the hardness of woods may require different clearance dimensions. In general, the harder the
wood, the smaller this clearance must be. The chain must be held firmly and in a straight line during the filing operation.
Use two straight steel bars 18-inches long, held in a vise to hold the chain teeth straight and level. A straight edge and
feeler gage should be used for constant checking of tooth height and clearances.
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