RATE OF FEED
The whole "secret" of professional
routing and edge shaping lies in making a careful
set-up for the cut to be made and in selecting the
proper rate of feed.
The proper rate of feed depends on several factors:
the hardness and moisture content of the wood, the
depth of cut, and the cutting diameter of the bit. When
cutting shallow grooves in soft woods such as pine, a
faster rate of feed can be used. When making deep
cuts in hardwoods such as oak, a slower rate of feed
will be required.
The best rate of feed is one that does not slow down
the router motor more than one-third of its no-load
speed. If the router is fed too fast, it will take large
chips out of the wood and leave gouge marks, if the
router is fed too slow, it will scorch or burn the wood.
The right feed is neither too fast nor too slow. It is the
rate at which the bit is being advanced firmly and
surely to produce a continuous spiral of uniform chips
-- without hogging into the wood to make large
individual chips or, on the other hand, to create only
sawdust. If you are making a small diameter, shallow
groove in soft, dry wood, the proper feed may be
about as fast as you can travel your router along your
guide line. On the other hand, if the bit is a large one,
the cut is deep or the wood 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. You will learn by experience
from practice and use. The best rate of feed is
determined by listening to the sound of the router
motor and by feeling the progress of each cut. Always
test a cut on a scrap piece of the workpiece wood,
In general, if the material being cut is hard, the cutter
size is large, or the depth of cut is deep - maximum
1/8 in., then your router should be run at slower
speeds. When these situations exist, turn the variable
speed control selector until the desired speed is
Note: Carbide cutters cut at higher speeds than steel
cutters and should be used when cutting very hard
materials. Keep cutters sharp at all times.
Clean, smooth routing 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 severed chips. If your router is forced to move
forward too fast, the RPM 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 the router motor becoming overloaded.
Under extreme force-feeding conditionsthe relative
RPM 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), with resulting
splintering and gouging of the workpiece. See Figure 14.
Your router is an extremely high-speed tool (15,000 -
25,000 RPM no-load speed), and will make clean,
smooth cuts if allowed to run freely without the ovedoad
of a forced (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 router 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.