RWL wrote...

They warped a little after hardening and tempering. Is this just
something you have to live with or are there home shop tricks that
prevent this?

Yes, and yes. The presence of the bevel causes some warp. The quenching
technique contributes as well.

You can take advantage of the latter to counter the former. In general,
edge tools tend to warp so as to crown the bevel. That is, the surface
opposite the bevel will be concave. OTOH, the first portion of the steel
to hit the quench will "shrink" forming a concavity there. Consequently,
you can start the quench at the bevel in order to counteract it's
tendency to crown.

It takes some experimentation to determine the best angle at which the
tool should enter the quenchant, as well as the best agitation motion for
the tool while in the quench. Sometimes it's better to plunge with the
tool pointing straight down and then move it in the direction of the
bevel. Sometimes it's better to plunge the tool straight down, but held
at an angle so the the bevel hits the quenchant first, and then move the
tool straight up and down in the quenchant.

You can also reduce the amount of warping by clamping the tool between
two thicker pieces of flat steel, and heat treating the whole unit.

It's not that the warp is bad, but it takes a LOT of
grinding / honing to get the blade flat after it's hardened and
tempered. I didn't measure the warp, but my guess is that it's less
than 0.010" longitudinally.

That's really not too bad for a thin W-1 edge tool, but it can be done
with less warping.

Surface grinding can restore the tool to flat after hardening, but with a
1/8" thick tool, you must shim it carefully while grinding the first
side. Otherwise, the magnetic chuck will pull it flat(ter) and the tool
will be ground parallel, but not flat. It will spring back curved after
being released from the chuck.

If you surface grind the part flat after quenching, you will need to
surface grind the bevel also. Still, it is better to rough out the bevel
before hardening, so as to minimize the amount of grinding needed on the
bevel after hardening. Unless you have flood coolant, it is very easy to
overheat the tool's working edge while grinding the bevel. Mist coolant
is inadequate unless the metal is removed at a snail's pace.

Are there belts specifically intended for metal grinding
that will do a faster job?

Aluminum zirconia belts (sometimes called blue belts) are the ticket for
fast(er) stock removal. However, the belt grinder will leave you with
convex rather than flat surfaces.

Is Water hardening tool steel is more prone to warping than oil
hardening?

Yes. But the quenching technique can have a greater effect on the degree
of warping than the difference between W-1 and O-1.

Cheers,

Jim