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Jim Wilson
 
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Default Failure to get sharp

RWL wrote...

One thing that I notice is that I never get a wire edge on the
flat side when grinding or hand sharpening these. That is
probably a clue to something.


I agree. Given what follows, the most likely suspect is honing technique.
Without knowing your proficiency at honing this kind of edge, it's hard
to say, but if you don't raise a wire, you're simply not going to get a
very sharp edge.

Are you honing both sides of the edge? What is the shape of the blade? If
it's a woodworking blade like a plane iron or chisel, are you flattening
and honing the face (I.e., the back) first? What type and grit of
stone(s) are you using?

It's the same composition as their drill rod which is listed as W-1.


So, it's safe to assume W-1.

I heated the blank with a torch till it was red hot and it was no
longer attracted by a magnet. ... After rapid quenching in water with a
stirring motion, a file would no longer cut the steel.


Now it's hard. So far, so good.

I tempered in a toaster oven.


Ok...

The first blank was ground to its intended angle BEFORE tempering.


Between hardening and tempering? Or before hardening (heat/quench)?

Generally, rough shaping/grinding is done before hardening.

I gournd slowly and no oxide colors developed on the blade edge
as I was grinding.


It's unnecessary to exercise so much caution before hardening. Finish
grinding (after hardening and tempering) is a different story;
overheating will ruin the blade's ability to take an edge.

I heated it for 30 min at about 450. I could see the
faintest of yellow oxide color on the blank.


If you cleaned the steel between hardening and tempering, it appears that
the true tempering temperature was under 400. No matter, though, that's a
good temper for edge tools.

I finished by hand stoning the edge...
It's sort of sharp - but like a dull plane blade. It just won't
get sharp.


The second blank I tempered before grinding it to an angle. In this
run, the oven was set to 400 for 30 min, raised to 450 and held for
another 15 min. The blank never got the oxide color. When ground
this one doesn't take an edge either, and doesn't feel quite as
"sharp" as the first one.


If you don't overheat the edge while grinding, it won't affect the
maximum sharpness that the edge can take. However, it's generally a good
idea to temper immediately after hardening, to prevent other bad things
from happening. Rough grind before heat treatment, finish grind and hone
after.

Has anyone had this experience?


It used to be hard for me to get a razor-sharp edge on my plane irons and
chisels. Eventually, I just got the hang of it.

Are they so hard that the edge is breaking off


No. Even at full hardness (no temper), that could not happen with this
type of steel at the grit ranges of any stone intended for honing.

or am I missing something else?


Possibly, but there's not enough info here to know. You've got (or you
had) the thermal processing well enough in hand to make a good edge tool.
The clues to that are (1) you identified the type of steel, (2) you got
it hard (file wouldn't cut it), (3) you succeeded in tempering it (pale
yellow color, and the tool didn't break), and (4) you didn't destroy the
temper (no temper colors while grinding). That pretty much leaves honing.

Good luck,

Jim