The most
common version of the straight router bit is a straight-fluted
bit. This comes with either one cutting edge (single flute) or two
parallel cutting edges (two flutes) that will do an acceptable job on
most cutting tasks. Straight-flute bits with one cutting
edge are the only bits that come in very small sizes
for routing inlays or other small jobs (there isn't much room on
a 1/16 bit for two flutes). In larger sizes, this design cuts faster but
with a slightly rougher quality than with other style bits. Wooden pattern Maker in India, Wooden pattern Maker in Ahmedabad
Those
with two cutting edges are ideal for cutting rabbets or dadoes on the
edge of a board, or for through-cuts in the center of a board, where the bit is
entering and exiting the workpiece as it cuts. They are also a good choice for
shallow mortises, such as hinge mortises, where you increase the depth of
cut slightly with each pass. However, straight-flute bits don't
plunge straight down into wood very well because the cutting edges are on
the side, not the bottom.
If you
need to plunge straight down into a workpiece, such as when cutting
mortises or stopped dadoes, you have two choices, either a straight-flute bit
with an added point on the bottom, or a bit with cutting edges on the end that
extend to the center of the bit. The former is a specialty item,
often with an angled tip like a drill bit. The latter is usually found on
spiral-flute bits.
In
addition to being ideal for plunge cuts, spiral-flute bits (also known as
shearing bits) leave high-quality surfaces. They are available with
the cutting edge on the upcut and downcut. Spiral upcut bits tend to tear out a
bit more on the top surface, since they are lifting the wood, but usually leave
the bottom surface in excellent shape. The reverse is true for spiral
downcut bits. A third style, known as a compression bit, is
designed to cut the top and bottom edges cleanly--a plus for routing
the edges of difficult plywood, for example. Wooden
pattern Maker in India, Wooden pattern Maker in Ahmedabad
Spiral
upcut bits often are used for mortising, because they clear the wood chips
better than straight-flute bits. There is a tendency to tear out at
the ends of the cut, but this is not usually a major issue. Because
of the complex machining processes used to make spiral-flute bits,
they cost more than straight-flute bits.
