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PROPER
RATE OF FEED
Professional trimming and edge shaping depend upon
careful set-up and selecting the proper rate of feed.
The proper rate of feed is dependent
upon:
[] the hardness and moisture content of the workpiece
[] the depth of cut
[] the cutting diameter of the cutter.
When cutting shallow grooves in soft woods such as
pine, a faster rate of feed can be used. When making cuts
in hardwoods such as oak, a slower rate of feed win be
required.
Several factors will help you select the proper rate of feed.
[] Choose a rate that does not slow down the trimmer
motor.
[] Choose the rate at which the cutter advances firmly
and surely to produce a continuous spiral of uniform
chips or a smooth trim edge on laminate.
[] Listen to the sound of the trimmer motor. A high-
pitched sound means you are feeding too slowly. A
strained, lower-pitched
sound signals force-feeding.
[] Check the progress of each cut. Too-slow feeding can
cause the trimmer to take off in a wrong direction from
the intended line of cut. Force-feeding
increases the
strain of holding the tool and results in loss of speed.
[] Notice the chips being produced as you cut. if the trim-
mer is fed too slowly, it will scorch or burn the wood. if
the trimmer is fed too fast, it will take large chips out of
the wood and leave gouge marks.
Always test a cut on a scrap piece of the workpiece wood
or laminate before you begin. Always grasp and hold the
trimmer firmly with both hands when trimming.
if you are making a smalPdiameter, shallow groove in soft,
dry wood, the proper feed rate may be determined by the
speed at which you can travel the trimmer along the guide
line. if the cutter is a large one, the cut is deep or the
workpiece is hard to cut, the proper feed may be a very
slow one. A cross-grain
cut may require a slower pace
than an identical with-grain cut in the same workpiece.
There is no fixed rule. Proper rate of feed is learned
through practice and use.
FORCE
FEEDmNG
See Figure 8.
The trimmer is an extremely high-speed tool (25,000/min),
and will make clean, smooth cuts if al!owed to run freely
without the overload of a forced feed. Three things that
cause force feeding are cutter size, depth of cut, and
workpiece characteristics.
The larger the cutter 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 laminate trimming and edge shaping can
be done only when the cutter is revolving at a relatively
high speed and is taking very small bites to produce tiny,
cleanly-severed
chips, if the trimmer is forced to move
forward too fast, the speed of the cutter becomes slower
than normal in relation to its forward movement. As a
result, the cutter must take bigger bites as it revolves.
Bigger bites mean bigger chips and a rougher finish. Big-
ger chips also require more power, which could result in
overloading the motor.
Under extreme force-feeding
conditions, the relative
speed of the cutter 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.
TOOSLOW
TOOFAST
Fig. 8
TOO
SLOW
FEEDmNG
See Figure 8.
When the trimmer is advanced into the work too slowly,
the revolving cutter does not dig into new wood fast
enough to take a bite; instead, it scrapes away sawdust-
like particles. Scraping produces heat, which can glaze,
burn, or mar the cut, and can overheat the cutter. Dull cut-
ters can also contribute
to scraping and burning.
it is more difficult to control a trimmer when the cutter is
scraping instead of cutting. With practically no load on
the motor, the cutter wil! be revolving near top RPM, and
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.
13
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