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Ed Huntress
 
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Default Failure to get sharp

"Jim Wilson" wrote in message
k.net...
Ed Huntress opined...
I suspect coarse grain. But that's not certain.


Ah, that did not occur to me.

OTOH, W-1 ordinarily has a rather fine grain, doesn't it? And it's quite
a forgiving material to work with.


Yes to both. But you can coarsen the grain by overheating, and it doesn't
take a lot of overheating to do it, if you soak it for more than a few
seconds. Water-hardening (essentially plain, high-carbon) steel is
forgiving, tolerating some mistreatment, but it's also quick to go to hell
if you mistreat it beyond its limits.

I switched to oil-hardening for small tools years ago, mostly because
quenching is less critical.

Of course, I must say that overheating during hardening definitely does
something, and I believe it is what you are talking about. I think I have
witnessed grain growth in particular (ahem), by intentionally breaking
pieces just hardened at various temperatures. The grain pattern at the
fracture looks distinctly coarser or finer, depending on the sample. Am I
really seeing variations in the molecular grain structure, or is that
something that requires magnification or sample preparation techniques.
If that's not what I'm seeing, then what might it be?


You're seeing grain. I don't know if the actual texture reflects individual
grains, but there is a direct correspondance between grain size and the
visible coarseness of grain at a break.

Ed Huntress