Craftsman 315.115830 Operator's Manual page 17

FEEDING TOO FAST/FORCE FEEDING
See Figure 13.
The trimmer is a high-speed tool (28,000/min.), and will
make clean, smooth cuts if allowed to run freely without
the overload of a forced or too-fast feed. Three things
that cause force feeding are bit size, depth of cut, and
workpiece characteristics. The larger the bit or the deeper
the cut, the more slowly the trimmer should be moved
forward. If the wood is very hard, knotty, gummy or damp,
the operation must be slowed still more.
Clean, smooth trimming and edge shaping can be done
only when the bit is revolving at a relatively high speed
and is taking very small bites to produce tiny, cleanly-sev-
ered chips. If the trimmer is forced to move forward too
fast, the speed of the bit becomes slower than normal in
relation to its forward movement. As a result, the bit must
take bigger bites as it revolves. Bigger bites mean bigger
chips and a rougher finish. Bigger chips also require more
power, which could result in overheating of the motor and
lower battery life.
Under extreme force-feeding conditions, the relative
speed of the bit can become so slow - and the bites it has
to take so large - that chips will be partially knocked off
rather than fully cut off. This will result in splintering and
gouging of the workpiece and will likely damage the tool.
FEEDING TOO SLOW
See Figure 14.
When the tool is advanced into the work too slowly it
scrapes away sawdust-like particles instead of cleanly
cutting into the workpiece. Scraping produces heat, which
can glaze, burn, or mar the cut, and can overheat the bit.
Dull bits can also contribute to scraping and burning.
It is more difficult to control a trimmer when the bit is
scraping instead of cutting. With practically no load on
the motor, the bit will be revolving near top RPM. When
feeding too slowly, the bit will have a greater than normal
tendency to bounce off the sides of the cut, especially
if the wood has a pronounced grain with hard and soft
areas. The cut that results may have rippled sides instead
of straight.
TOOSLOW
Fig. 14
TOOFAST
Fig. 13
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