Love Your Saws with Matthew Cianci


 
 

I slope, you slope, we all slope gullets

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At 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. 

Like this…

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?

Two things:

  1. Slope 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.

  2. Slope 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!


 
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