David Weaver
..is quickly learned using a wrought iron backed japanese tool on a cast plate for loose diamonds.

It's certainly reasonable to say "why? ....would anyone do that?", but sometimes something is at hand and you use it rather than faffing with anything else.

The wrought jigane will instantly get in a war with cast, and you just can't get away with it no matter how tempting.

But other than wearing the glass, I got along fine with what warren's mentioning, too - just not for any heavy flattening as i often like to do with a new to me stone. plastic laminate would come up short for that, too - I'm looking to remove 1/4" of dish in 10 minutes and not hours, so the belt sander for the rough work on the ends is the way to go, but even then - the edge of the idler and not working on the platen.

If precision is necessary (like you're talking about, grinding lenses), then rolling abrasive is no good. It works OK for truing oilstones, though, and is intentionally what we're doing using a slurry on natural japanese stones.