some point in your handsaw journey you’ll probably come across
the term ”sloped gullets”, and at first you’ll likely be as
confused as a drunken sailor about what the heck they are.
So what is a gullet, and why do I want it sloped?
The gullet is the space between the points of saw teeth, and
their function is to collect the sawdust that is created by the
working edge of each tooth. And just like these working edges on
the teeth, the geometry of the gullets can be manipulated by the
file as you sharpen the saw.
Slope generally refers to the shape of the bottom of the gullet,
or more specifically, the angle of the bottom of the gullet
relative to the side of the saw plate. Conventionally, saws are
filed without slope, and the bottom of the gullet is 90 degrees
(square) to the side of the plate. This is called “zero slope”. When you file a saw and hold the file parallel with the floor,
or perpendicular to the saw plate, you create a square bottomed
gullet, i.e. zero slope.
Slope is created by lowering the file handle when you sharpen a
saw, and is measured in degrees from perpendicular to the saw
plate. It looks like this…
See the difference? Everything else is the same… same rake
angle, same fleam angle but I lower the file handle. And
that’s how you introduce slope to saw teeth. You can vary the
amount of slope from 0 to 45 degrees.
So what effect does this have on the saw teeth?
removes more material from the bottom of the gullet
(steel from the saw plate) and allows a greater capacity
to collect sawdust. The more sawdust the gullets can
contain, then the more work the teeth can do before
bottoming out in the kerf. Deeper gullets = more work =
faster cutting saw.
allows the filer to control the bevel on the back of
each tooth independently from the front bevel. In
effect, you can put fleam on the front of the tooth, but
keep the back square (or give it a lower amount of fleam).
What good is this? It makes for a more robust included
angle at the working point of the tooth without
sacrificing fleam, and thus the teeth stay sharp longer.
Make sense? Good, because its not supposed
to. Just kidding!