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Bar maintenance is a very critical factor in the operation of today's high
speed, high-horsepower saws.
Stop for a moment and think about how much chain is traveling around the
bar in one second's time. About 80 feet of chain pass one spot on the bar
in one second. Over an hour's time, that amounts to almost 300,000 feet, or 53
miles of chain. Given this speed and the light lubrication which the chain
and bar receive, both the bar and chain are subject to wear through normal
use.
Where conditions of abnormal wear exist, they are often the result of poor
maintenance practices. The faults are usually poor sharpening of cutters,
loose chain tension, or inadequate bar and chain lubrication.
The wear pattern on the bottoms of cutters, tie straps and drive links
generally reflects the condition of your bar. Regular inspection of the
chain will point out the need for corrective maintenance. Correct problems
immediately and you can avoid further damage, or replacement of the bar or
chain, or both.
Here are some examples:
1. If the bottoms of the drive links are
worn flat, like the shaded area, the bar groove is shallow either in the
tail or straight section of the bar. (see A)
2. If the bottoms of the drive links are worn concave, the bar groove
is shallow in the bar nose. Most likely, the stellite material on a hard-nose
bar has worn off. (See B)
3. If the bar rails are not flat and square, the chain parts will
wear like this. (See C)
4.
If the bar rails are uneven, the chain parts will wear like this. (See
D)
How to check bar groove wear:
First, tension the chain. Then, place a straightedge against the bar and the
cutting edge of one cutter. Force the cutter sideways as far as it will
go. There should be a 1/16 to 1/8-inch gap between the straightedge and
the side of the bar. The chain should be supported squarely by the bar
rails. If it isn't, it's time for a new bar. (See E)
To get better service from your bar, check it daily for the
following:
1. Bar rails flat and even. Both rails must be flat and square with
the sides of the bar. The original shape or contour of the bar must be
maintained. (See F)
2. Correct bar groove width and depth. The groove width should be from
.002" to .005" wider than the gauge of the chain being used. Groove depth should
range between a minimum of 5/16" and a maximum of 27/64". (See G)
3. Check your bar by sighting down it to see that it is straight. A bar
can be bent in an operating accident and the user will not be aware of it.
Bent bars should be straightened immediately or further damage will occur to
both bar and chain.
General maintenance techniques:
Because the chain and bar operate together as a team, a few simple practices
can make them both run efficiently.
1. Keep your cutters sharp and touch them up frequently.
2. File the cutters evenly. Be sure the filing angles are the same on
the left and right sides.
3. Keep your depth gauges even on both sides of the chain and at their
recommended settings.
4. Use plenty of bar and chain oil. Oil is cheaper than either a new
bar or chain!
5. Remove the bar periodically and clean accumulated sawdust from the
oil hole and bar groove. Turn the bar over regularly.
6. Tension the chain properly, just tight enough to be able to pull
around the bar by hand. Check the tensioning frequently, but not while the
chain is hot; wait until the chain is cool to the touch.
At a speed of 53 miles per hour, four hours of saw running time
means 200+ miles of chain passing over the bar. Attention to the condition
of the chain and bar, plus frequent lubrication, will safeguard your
equipment investment. In reduced wear alone, you'll more than pay for the
oil you use. |
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At a speed of 53 miles per hour, four hours of saw
running time means 200+ miles of chain
passing over the bar.
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