NOTE:
This
describes how I test my knives. Anything and everything
in a knife shop is dangerous. These
tests can be extremely dangerous and I am not
suggesting that you should try it. If you are not an
experienced knifemaker, I'll tell you outright, "DON'T
DO IT". When I perform these tests, especially
the bend test, I have someone near by in case something
goes wrong. I also wear eye protection, thick gloves,
and a heavy leather apron.
A
few years ago I would make knives and give them to
friends and relatives to test. There was always that
uneasy feeling that I might not have gotten everything
right. Would the blade work properly for its intended
purpose? Would the edge hold up? Would the knife
be able to take much abuse? I was really concerned
that I might have to wait a couple of years before
any problem surfaced. And during that waiting period,
any knives I made had the potential of suffering
the same problem.
The solution was quite simple, but it took advice
from ABS Master Smith Jerry Fisk to bring the answer
to light. Test every blade after heat treating.
Use it hard. Occasionally take one to the point of
destruction. Then you'll know what your knives will
do. Listed below are some of the steps I use.
Standard
Tests
- I
have several sections of 2x4 studs with big knots
in them stored in my shop. After heat treating,
I put a temporary edge on the blade and sharpen
it to the point that it will cleanly slice though
a cigarette paper. I then hack on one of the knots,
working up and down the edge. After doing this
I inspect the edge very carefully for damage. The
way I resolve any problem with edge damage depends
on what the damage is. More information on this
follows.
- If no damage occurred,
I check to make sure
that the blade will
still shave hair from
my arm.
- For
larger
blades
like
Bowies
and
camp
knives,
I
then
chop
a
2x4
in
half
twice.
Again
I
check
for
damage
and
if
none
is
found,
make
sure
it
will
still
shave
hair.
It
would be
easy
to
cheat,
but
that
would
defeat
the
whole
purpose.
When
checking
for
shaving
sharpness
you've
got
to
test
the
area
of
the
blade
that
took
the
most
abuse.
It's
easy
to
tell.
That
area will
usually have
streaks on
it from
the chopping
and/or tiny
little pieces
of wood
on the
edge. If
everything is
okay at
this point
and the
blade is
not one
to be tested
to the
point of
failure, then
the test
is finished.
- Occasionally
I
will
take
a
blade
to
the
point
of
destruction
to
see
how
tough
it
is.
I do
this
by
clamping
1/3
of
the
blade
in
a
vise
with
the
tip
pointing
straight
down.
I
then
slip
a
3
to
4
foot
cheater
pipe
over
the
handle.
Next
I
carefully
bend
the
blade.
If
the
blade
was
differentially
heat
treated
with
a
hard
egde
and
a
spring
tempered
spine,
it
should
bend
to
90
degrees
without
breaking.
Otherwise
the
blade
should
not
fail
until
it
has
been
bent
approximately
45
degrees.
The
cheater
pipe
is
not
just
to
get
me
a
little
farther
from
the
blade, it
is also
for more
leverage. Unless
the blade
was forged
pretty thin,
I can't
bend it 90
degrees or
break it
by hand.
Other
Tests
A good
test for a blade is cutting rope. Rope cutting can
wear down an edge pretty quick. One of the performance
tests for a prospective ABS Journeyman or Master Smith
is to cut a one inch free hanging sisal or manilla
rope in one movement. I have stretched a piece of rope
across a board and cut it up like a piece of sausage
on occasion. Cutting up cardboard boxes is another
good test. I've also been known to hack a limb off
a tree every now and then.
Reading
the Edge
Sometimes
damage may be obvious. Other times there may be some
type of damage that doesn't really jump out at you.
This is how I inspect for damage. First I look all
over the edge with a magnifier. I use an opti-visor
like you might see a jeweler wear. I will also very
gently, carefully, and slowly drag the edge across
the edge of a fingernail. Any catching or snagging
can indicate a chip in the edge. A sort of slip or
small bumping feeling can indicate a flat spot in the
edge. A good (and safer) way to find a flat spot is
to take the knife out into the sunlight. Hold the blade
edge up. Slowly rock the blade and look for a shiny
little glimmer in the edge. A flat spot, no matter
how small will reflect light like a facet on a diamond.
Fixing
Problems
A chipped
edge means the blade was not drawn back enough after
hardening. If this ever happens, I take the blade back
to the draw (tempering) phase to remove more of the
brittleness. I keep records of the hardening and tempering
temperatures that I use for various types of steel.
The only time I really have this problem is when experimenting
with a new type of steel.
A flat spot in the edge means it was drawn back
too much. To fix this I would have to go all the
way back to the hardening phase. Again, because I
keep records of successful heat treat temperatures,
I seldom have to deal with this unless experimenting
with a new type of steel.
If the edge has just a tiny little crinkled look,
then the edge is just a bit too delicate. This is
an easy fix. I just beef it up some at the grinder
and try again. Now understand, when I say tiny little
crinkled edge I do mean tiny. If it looks
like a hacksaw blade, I've got a problem. I would
go back to the hardening phase.
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