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In the upper part of this shot, you can see a
goodish surface, but notice the lines running
the length of the work. They're very faint
and can't be felt by hand, but they are
there. I think that they're the marks of
tool vibration caused by the chain drive.
The Logan shaper is driven by a chain running
on two sprockets. When sprockets wear, they
tend to develop a bit of a hook in each
tooth. The hooks grab the chain a little
bit, possibly causing these small ridges in
the surface.
I may replace the chain, but that's risky. A
chain and a sprocket tend to wear together.
If the wear is severe enough, a new chain
will run worse than the old. It will have
short links, while the teeth will want
slightly longer (worn) links.
In any case, a final cut of about .001" seems
to get rid of the ridge pattern, leaving a
better finish. You can see that near the
bottom of the photo, below the line of dust
shaved from the iron by the cutter.
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