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RWL
 
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Default Failure to get sharp

On Tue, 07 Oct 2003 04:05:12 GMT, Jim Wilson
wrote:

Thanks Jim.
The detail in the post is helpful.

RWL


One thing I've noticed is that the emery paper gets dull pretty
quickly. I'm only using strips about 3" wide and 6-7" long.
I'm using 100, 180 400 and 600 grits.


Ok, to keep our terminology straight, I'll call the flat side the "back,"
too.

Some of this stuff I'm going to say is not strictly necessary, but if you
follow all of it, you should achieve success. The not-strictly-necessary
stuff can be figured out and eliminated or altered later after you are
happy with your results. Also, please forgive me if I'm telling you
something you already know or are already doing. I'm just trying not to
leave anything out.

First, finish the back all the way to your finest grit before starting on
the bevel. Then begin with the coarsest grit on the bevel, and work your
way through all the grits. Don't skip any. The ones you have will work
ok, although there is a better (faster) sequence. Ideally, the particle
size of each level should be about 1/3 the size of the previous level. I
can give you details on that if you're interested.

Stay with a grit until all the scratches from the previous grit are gone
and you have a uniform pattern of new, smaller scratches from the current
grit all over the surface, or whatever portion of it that you are
working. Keep the pressure firm, but not heavy. Make the final five or
six strokes for a grit lighter.

Alternate the stroke angle slightly for each grit to make it easier to
tell when the coarser scratches of the previous grit are gone. For
example, if you line up the edge at one o'clock for one grit, line it up
at eleven o'clock for the next one.

Keep the paper clean and it will cut better. An occasional blast of
compressed air will clear it quickly (please wear safety glasses if you
do this).

When working the back, make your strokes approximately parallel with the
edge. The strokes of the final grit should be really close to parallel.
You only need to hone about 1/2" to 1" back from the edge; there's no
need to do the whole back. Also, you can stop as soon as the uniform
pattern of scratches touches the edge everywhere. If you've followed Ed's
advice on quenching, you'll probably notice that the edge is dished just
a bit; I.e., the back is slightly concave. This is good; it makes the
back go much faster.

When doing the bevel, make your strokes approximately perpendicular to
the edge. Stay with the coarsest grit until you have raised a burr along
the whole edge. It will probably start coming up in the middle, so keep
working until it reaches the ends. Do not bend or break the burr. It will
form much easier and faster if you stroke only away from the edge (as you
described above for the first part of your stroke), especially given the
abrasives you are using. This is because the paper backing has a little
"give" and the blade sinks into it a bit.

As you progress through the grits, the burr will shrink, and pieces may
break off. Clear them from the paper, but do nothing to the edge. When
you are finished with the finest grit, the burr may be quite small, but
it should still be detectable by the edge your fingernail.

The proper way to remove this burr is with one or two light strokes on
the back with the finest grit. Resist the temptation to raise the blade
during this stroke; keep it flat on the abrasive.

If the burr is heavy, it may bend over to the bevel side before being
ground completely away. If so, you'll be able to feel it with your
fingernail. Remove it by repeating: four or five strokes on the bevel,
followed by one or two strokes on the back. When your fingernail can no
longer detect the burr on either side of the edge, you're done.

By the way, 600 is really the lowest grit you can stop at for a decently
sharp edge. I assume that your 400 and 600 grits are silicon carbide
paper. You would do better to go at least to 1000, and many folks go a
good bit higher. 2000 SiC paper has about the same particle size as an
8000 grit Japanese waterstone, and although the particle geometry,
hardness, and friability are different, either can produce a hair-
splitting edge.

There are other ways to get a good edge using the SS system. Brent Beach
is a proponent of microbevels, and has developed a good method of quickly
getting the type of edge that he likes. You might have a look at his
site:

http://www3.telus.net/BrentBeach/Sharpen/overview.html

Please also check Ed Huntress's suggestion that grain growth could be a
problem. You might be overheating the tool during hardening. If the
process above doesn't work, then grain growth could be the culprit. In
that case, your best bet might be to start over with new steel, although
with care (and, unfortunately, either experience or luck), the old steel
could very well be salvageable.

Thanks Jim. I'm strongly beginning to think I must be doing the
honing wrong.


My pleasure, and good luck.

Jim


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