In article , Dave Baker wrote:

You want a Dremel or similar. A small stone running at high speed will
remove metal without wearing itself out. The key is surface speed which is
ideally the same for all grinding wheels. Basically an inverse relationship
between diameter and rpm. The technical term is SFM (surface speed per
minute). I have professional cylinder head porting gear but then that's what
I do (did) for a living and a 1 inch diameter stone running at 15000 rpm
will sharpen anything to a razor edge with no discernable wear on itself. I
use mine on the shears, secateurs and lawnmower blades.

Thanks very much. I was hoping to avoid yet more clutter, but it
sounds as if the advance of modern technology has done for me :-(

By the look of their description, I shall have to buy something for
drill bits, too, which I used to sharpen by hand (not brilliantly,
but well enough).

A bench grinder is not ideal as you say because it has too many bits in the
way for a long blade like a scythe. Even something as big as a 4" stone in a
normal drill is no use because the surface speed is too low.

Oh, they work, all right. But they eat stones. Not a problem when
I don't do a huge amount, and 4" stones were easily available, but
that is no longer the case.


Regards,
Nick Maclaren.