Christopher Dunn wrote:
> Galoots
>
> I bought a huge wooden panel raiser plane with a 4-1/4" wide tapered
> iron, and started flattening the back of the iron on my coarse diamond
> stone. Five hours later, and only about half the cutting edge is flat
> (the two corners are low). I've never dealt with such a wide blade
> before, but there's got to a better way.

Given that the progress pattern when flattening is one
of slowing down (the small high spots are dealt with quite quickly),
you're not even close to halfway through.

You need faster, coarser abrasive; I suggest cloth backed ALZI
at around 40-60 grit, backed by something flattish and stiff.
Use moderate pressure to avoid stripping the grains
from the backing.

With such a wide blade, you also have an issue with
potential convexity introduced by the flattening process,
so watch out for that.

    BugBear