Stihl OILOMATIC Manual page 28

3.17 Use of Saw Chain
3.17.1 Mounting the Saw Chain
Installation of the chain is similar on
all STIHL chainsaws and is
described in the instruction manual
supplied with the saw.
There are a few important points
which should be noted:
– The chain length (number of drive
links) must match the length of
the guide bar.
– The chain pitch must match the
pitch of the chain sprocket and, in
case of Rollomatic guide bars,
also match the pitch of the nose
sprocket.
– The drive link gauge must match
the width of the guide bar groove.
– The guide bar tail must fit the
powerhead.
As a chain sprocket normally has a
wear life equivalent to two saw
chains, it is advisable to use two
chains in rotation with one sprocket.
In this way the sprocket and chain
bed in with each other and wear out
together. If a new chain is installed
on a half-worn sprocket, its drive
links will wear very quickly.
The following rule of thumb is a
good guide for economic operation
of a chainsaw: Always use
– one guide bar
– two chain sprockets
– four chains
in rotation.
Chain and Bar Manual
3.17.2 Chain Tension
Correct tension, lubrication and
maintenance of the saw chain are of
great importance to the service life
of the chain, guide bar and chain
sprocket. They also have a major
effect on the wear life of engine
components.
The procedure for properly
tensioning the chain is described in
the instruction manual supplied with
every STIHL chainsaw. The cold
tensioned chain should fit snugly
against the underside of the guide
bar so that it can still be pulled along
the bar by hand.
Always wear suitable protective
gloves to reduce the risk of direct
contact with the sharp cutters.
During cutting the chain warms up
as a result of friction and expands.
This causes the chain to slacken
and eventually sag on the underside
of the bar.
If the saw is being used at extremely
low outside temperatures, the chain
will sag so much when it reaches
normal operating temperature that it
will have to be retensioned. The
chain must always be slackened off
again during long work breaks.
If this is not done the chain would be
over-tensioned as it cools down to
ambient temperature and finally
break and damage the crankshaft
and bearings in the process.
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