I've never tried it, but have heard the old timers used to use
this same technique to 'sharpen' files as well.
Hey c’mon, it’s not just the old timers. the method’s been
published widely for a long time, though not widely touted or taught
in the schools. but for many of us, it’s been routine for years, and
I’m not all THAT old (I hope). It works better for burrs than for
files, as files seldom seem to cut quite as evenly after acid
sharpening, especially fine cut ones. Coarser files work better. they
don’t stay sharp quite as long (burs either, though less noticably)
since the etch tends to produce a “wire edge” on the cutting edge
that is initially sharp, but breaks off, leaving a less sharp edge.
On a bur, you don’t notice it so much, but with a file, sometimes you
end up with a sharp, but scratchy file that doesn’t leave a surface as
even as you’d like. Also, nitric isn’t the only acid that you can
use. HCL works well, and in a pinch, I’ve even used some older
pickle, though that isn’t as effective…But on a dull burr when you
don’t have another acid right handy, or another of the right size
Another use for the acid bath is to taper the ends of wire
for inserting into a draw plate when drawing wire. The acid needs
to be changed for gold however.
or gold use aqua regia. But faster even than just a plain acid etch
is an electroetch. You can even use just standard electrostripping
solution. Some of them will work with either silver or gold.
Usually cyanide based though… With silver, nitric and low voltage
is very fast. With gold, aqua regia with low voltage is also
efficient, though a good cyanide electrostripping solution is also
quite fast here. The method is less effective on larger wire sizes,
but when the wire gets fine enough that it’s hard to hold and hard to
file a new point on, 'cause it’s too fine, then the electrostrip
methods really shine, and are quite fast.