Having sharpened a few saws recently, I thought I'd
publish some of my experiences.
In places these contradict Pete Taran's advice.
I think this is because Pete's too darn good
at sharpening saws, and has assimiliated some skills
so deeply that he's forgotten ever having to be
concious of them, and thus doesn't mention them.
I therefore subtitle these observations
"Hints on saw sharpening from a beginner,
for a beginner"
At the earliest stage (topping and jointing) you might
also want to check (with a straight edge) the
overall shape of the edge, and adjust it to either
be straight or breasted, depending on the purpose
of the saw. On one of my saws I forgot to do
thi check, and ended up with a well sharpended saw
with a cosmetically irritating bump in the edge;
removing this at an early stage would have been trivial,
but it would now involve resharpening the saw.
Lesson learnt :-(
I found that judging "removing half the flat"
on each of the 2 passes very difficult. I have
settled on an iterative process, removing "some
of the flat" on each pass. I simply repeat this
until there is no flat (AKA "shiner") left.
From memory, I'm doing about 8 passes at the moment.
No doubt as my skill, judgement and confidence increase
this will reduce.
Observing exactly when the flat disappears can be
tricky. A particular problem is that as the tiny last
vestige of a flat disappears, a tiny filing burr
*APPEARS*. Depending on your lighting and eyesight,
this burr can reflect light a little like a flat,
so you keep on filing... (BAD).
If your saw vice is not perfectly even, some parts
of you saw will be better held than others.
As Pete comments, if your saw is not held well, it
will vibrate, and your filing will be less effetive.
The corrollary of this is that if your saw is not
held uniformly, a single file stroke will remove
different amounts of metal depending on where is
the vice you are working. This caught me out a
couple of times.
I have settled on a procedure of applying the set to the
saw just before the final 2 passes (of my multi-pass approach).
I noticed that it was quite hard to see the flats during
these final passes. On a coupla' saws I just ascribed this to
the fact that the flats were getting small, but I then realised
the problem was the set - when the set has been applied the original
flats are no longer co-planar, which make seeing them difficult.
My solution was to perform an extremely gentle topping pass,
just so the flat on the opposite facing teeth once again reflect
light from the same angle, and are thus simultanesouly visible,
making judgement much easier.
BugBear (who has finished saw sharpening for the moment)