Too Slow Feeding; Depth Of Cut; Direction Of Feed And Thrust - Craftsman 315.175070 Owner's Manual

TOO SLOWFEEDING
It is alsopossible tospoila cutby moving the router
forward too slowly. When it is advanced into the work
too slowly, a revolving bit does not dig into new wood
fast enough to take a bite; instead, it simply scrapes
away sawdust-like particles. Scraping produces heat,
which can glaze, burn, or mar the cut -- in extreme
cases, can even overheat the bit so as to destroy its
hardness.
In addition, it is more difficult to control a router when
the bit is scraping instead of cutting. With practically
no load on the motor the bit will be revolving at close
to top RPM, and will 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
rippled, instead of straight sides. See Figure 14.
=Too-slow feeding" can also cause your router to take
off in a wrong direction from the intended line of cut.
Always grasp and hold your router firmly with
both hands when routing.
You can detect =too-slow feeding" by the runaway
too-highly pitched sound of the motor; or by feeling
the "wiggle" of the bit in the cut.
DEPTH OF CUT
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 router motor and bit). 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 bit is no longer cutting, it is scraping, instead.
Making a deep cut is never advisable. The smaller
bits -- especially those only 1/16 inch in diameter --
are easily broken off when subjected to too much side
thrust. A large enough bit 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 bit as desired.
For these reasons, we recommend that you do not
exceed 1/8 inch depth of cut in a single pass,
regardless of the bit size or the softness or condition
of the workpiece. See Figure 15.
DEPTHOF CUT
WIDTH
OFCUT
Fig. 15
To make deeper cuts it is therefore necessary to
make as many successive passes as required,
lowering the bit 118 inch for each new pass. In order to
save time, do all the cutting necessary at one depth
setting, before lowering the bit for the next pass. This
will also assure a uniform depth when the final pass is
completed. See Figure 16.
2ND PASS
I
ISTPASS
2ND PASS
1STPASS
Fig. 16
DIRECTION OF FEED AND THRUST
See Figure 17.
ROUTERFEED
DIRECTION
4
ROUTl
END I
GRAINSJ
FIRST
I= ROTATION
ROUTERFEED
DIRECTION Fig. 17
The router motor and bit revolve in a clockwise direction.
This gives the tool a slight tendency to twist (in your
hands) in a counterclockwise direction, especially when
the motor revs up (as at starting).
Because of the extremely high speed of bit rotation
during a "proper feeding" operation, there is very little
kickback to contend with under normal conditions. How-
ever, should the bit strike a knot, hard grain, foreign
object, etc. that would affect the normal progress of the
cutting action, there will be a slight kickback-- sufficient
to spoil the trueness of your cut if you are not prepared.
Such a kickback is always in the direction opposite to the
direction of bit rotation.
To guard against such a kickback, plan your set-up and
direction of feed so that you will always be thrusting the
tool -- to hold it against whatever you are using to guide
the cut -- in the same direction that the leading edge of
the bit is moving. In short, the thrust should be in a
direction that keeps the sharp edges of the bit continu-
ously biting straight into new (uncut) wood.
16