In general
there are two types of bonsai tools: those that cut (scissors
and shears) and those that bite (branch cutters, knob cutters,
root cutters). Each of the two types must be sharpened in
a different way.
Cutting Tools
Examine the blades closely for nicks or burrs that might appear
on the inner face (flat surface) of the cutting edge.
In order to eliminate rough spots, use a fine grained stone
moistened with water or light oil. Place the stone flat on
the inside blade surface and remove the burrs as shown in
the sketch below.
Remove burrs on the inner surface of the blade
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It is important that the stone and blade be completely
flat against each other. It is also very important that you
stop as soon as the burrs are removed. Too much rubbing runs
the risk of deforming the cutting edge.
Now you are ready to sharpen. With the scissors open, firmly
place the inner flat side of the blade against a table top
or other flat surface. Hone the outside (angled surface) part
of the blade only. Try to maintain the original angle established
by the manufacturer. Keep each honing stoke parallel with
this angle as shown in the illustration.
Hone in one direction only; away from the cutting edge. Don't
scrub back and forth. Think of it this way; you are pushing
metal away from the cutting edge in order to sharpen it.
Don't over-do it. Three or four passes, done correctly,
should suffice.
Sharpening the outer surface of the blade
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To test the edge, place it lightly on your fingernail and
scrape it perpendicular to the cutting direction (never along
the cutting edge). If it slides over your nail, it is still
dull. If it catches, it is sharp.
Now turn the scissors over and repeat the process with the
other blade.
Wipe off excess oil and filings with a cloth. Some oil can
be left on the protect the tool. If you used water, be sure
to re-oil the tool.
Excerpted from Bonsai Today issue #6 (March-April 1990).
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