General Guide to Router Cutters
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The cutters that are used with a router have developed
over the last 35 years to allow a variety of tasks to be
obtainable with the use of a hand held power tool. These
developments have improved the work finish and more
importantly, the safety of the operator.
TCT (Tungsten Carbide Tipped) cutters have the main
body and shank machined from high grade steel but have
tungsten carbide tips brazed into each flute. This set up
gives alround benefits. The reduced rake angle helps to
reduce kickback and snatching. The TCT cannot be
honed to such a sharp edge as HSS but will last a lot
longer than HSS cutters. The better quality cutters
have a thicker section of carbide. The best carbide
cutters are produced with micro granular grades of
tungsten. The outer edge of the blade will be polished
and shiny (diamond sharpened) not dull and serrated.
Tungsten Carbide is extremely brittle and prone to
chipping if knocked or dropped; this is why it is important
to store your cutters carefully. Tungsten Carbide is suitable
for all round use including; natural timbers, manufactured
boards, plywood, chipboard, MDF, glass reinforced plastics,
acrylics and hard plastic like Corain.
History
High speed steel cutters (HSS) are ground out of a solid
piece of high speed steel. These are cheaper to produce
than TCT cutters, which is reflected in the price of the item.
These can be ground to a fine edge as the material is not
as hard as TCT but it does not hold the cutting edge as well.
Due to the angle of the rake, they are more prone to kick
back or snatching. They are suitable for use with non
abrasive natural timbers and PVC.
(HSS) High Speed Cutters
(TCT) Tungsten Carbide Tipped Cutters
(STC) Solid Tungsten Carbide Cutters
STC (Solid Tungsten Carbide) cutters are ground from a
solid section of tungsten carbide. These provide the best
durability when used a under stress load operation. Smaller
diameter cutters are ground from this as it is impossible
to insert a TCT in smaller sections. Solid Tungsten Carbide
is also better for operations where deep plunge cuts are
required, e.g. cutting mortise slots. These cutters have
a spiral section ground into the cutter face to remove the
waste mater.
Arbour Mounted Cutters
Arbour mounted cutters have a parallel shank (1/4” or 1/2”)
and a machine thread at the bottom. Interchangeable
cutters called “slot cutters” can be fixed onto these. The
use of shims, spacers, washers and a locking nut fix hold
the slot cutters on the cutter. It is possible to mount more
than one disc on these at a time. Care needs to be taken
when mounting the slot cutters as it is very easy to mount
these upside down. A good reference is viewing the
standard router cutter.
Pin & Bearing Guided Cutters
Within this range of cutters, there are a few that will be
classed as self guiding. These are;
• Pin Guided - these have a machined pin on the bottom
of the cutter body. They are cheaper to produce and need
extra care as it is possible to friction burn the work piece
using these.
• Bearing Guided - these have a ball bearing guide that
can be top or bottom mounted. The bearing is designed
to follow a template or run on the work piece itself.
Different sized bearings can also be fitted on some cutters
to increase or decrease the maximum depth of cut. Less
friction is created so the work piece will not be burnt.
The bearings to wear out but can easily be replaced.
