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FORCEFEEDING
Clean, s mooth laminate trimming andedgeshaping
canbedoneonlywhenthecutteris revolving ata
relatively h ighspeed andis takingverysmall b itesto
produce tiny,cleanly severed chips.If yourtrimmer i s
forcedtomoveforward toofast,thespeedofthe
cutterbecomes slower thannormal i nrelation to its
forward movement. Asa result, t hecuttermusttake
biggerbitesas it revolves. "Bigger b ites" meanbigger
chips,anda rougher f inish.Bigger chipsalsorequire
morepower, w hichcouldresultinthetrimmer m otor
becoming overloaded.
Under extreme force-feeding conditions t herelative
speedofthecuttercanbecome soslow-- andthe
bitesit hasto takesolarge-- thatchipswillbe
partiallyknocked o ff (rather t hanfullycutoff),with
resulting splintering a ndgouging oftheworkpiece.
See Figure 5.
TOO SLOW
TOOFAST
Fig. 5
Your trimmer is an extremely high-speed tool (23,000
RPM no-load speed), and will make clean, smooth
cuts if allowed to run freely without the overload of a
forced (too fast) 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.
You can always detect "force feeding" by the sound of
the motor. Its high-pitched whine will sound lower and
stronger as it loses speed. Also, the strain of holding
the tool will be noticeably increased.
TOO SLOW
FEEDING
It is also possible to spoil a cut by moving the trimmer
forward too slowly. When it is advanced into the work
too slowly, a revolving cutter does not dig into new
wood fast enough to take a bite; instead, it simply
scrapes away sawdust-like particles. Scraping pro-
duces heat, which can glaze, burn, or mar the cut-- in
extreme cases, can even overheat the cutter so as to
destroy its hardness. Dull cutters can also contribute
to scraping and burning.
In addition, 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 wilt be revolving at close
to top RPM, and wilt have a much 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). As a result, the cut produced may have sides
that are rippled instead of straight.
"Too-slow feeding" can also cause your trimmer to take
off in a wrong direction from the intended line of cut. You
can detect "too-slow feeding" by the high-pitched sound
of the motor. Always grasp and hold your trimmer
firmly with both hands when trimming.
DEPTH
OF CUT
See Figure 6.
As previously mentioned, the depth of cut is important
because it affects the rate of feed which, in turn,
affects the quality of a cut (and, also, the possibility of
damage to your trimmer motor and cutter). A deep cut
requires a slower feed than a shallow one, and a too
deep cut will cause you to slow the feed so much that
the cutter is no longer cutting, it is scraping, instead.
DEPTH
OFCUT
WIDTH
OFCUT
1ST.
2ND.
PASS
PASS
Making a deep cut is never advisable. The smaller
cutters --especially
those only 1.6 mm (1/16 in.)- in
diameter -- are easily broken off when subjected to
too much side thrust. A large enough cutter may not
be broken off, but if the cut is too deep a rough cut will
result -- and it may be very difficult to guide and
control the cutter as desired. For these reasons, we
recommend that you do not exceed 3.2 mm (1/8 in.)
depth of cut in a single pass, regardless of the cutter
size or the softness or condition of the workpiece. This
will result in a higher quality cut.
To make deeper cuts it is therefore necessary to make
as many successive passes as required, lowering the
cutter 3.2 mm (1/8 in.) for each new pass. In order to
save time, do all the cutting necessary at one depth
setting, before lowering the cutter for the next pass.
This will also assure a uniform depth when the final
pass is completed.
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