Is there a way I can flatten India stones that have wore to a non-flat shape? Most are medium grit, but some are fine grit, if that matters. Can you do this with a diamond stone or something? ANy suggestions would be appreciated

Rub them on a flat finished piece of concrete, your drive will do. Keep it wet.

I agree with Ol' Joe. I "freshen" my sharpening stones the same way. I do it dry (wet will work too I guess), and use a figure 8 patern swirling motion with light/moderate pressure to work the stone. Make a cetain number of figure 8's,(20?, not critical), and reverse the stone direction 180 degrees in your grip to uniform the freshening, and rub another number of figure 8's.

Also, giving the stone a blast of carbuerator cleaner (ie Gumout) from an aerosol can will clean up an oil saturated stone too. May want to try this before the concrete freshening.

I think that you will find that wet sandpaper on glass is a lot flatter than most driveways. Do use the figure 8 motion though. A little water or oil on the glass will stick the paper to it..................DJ

lightly press onto a flat belt sander 120grit.
turn the stone end to end then side to side.
Repeat until desired finish, flatness.
I do them dry. I clean the stones with spray on lps contact cleaner first. it evaporates and drys quickly
Dave

I got one of those cheap granite surface plates for 20 bucks at woodcraft...

I use spray glue and attach coarse emery cloth and use plenty of brake cleaner to clean flatten the stone dead flat- takes a bit of work but it's worth the results.

Don't scrub any grit off the surface plate-- gently rinse it off. The surface plate works great for sharpening with sandpaper also- especially chisels and planes...

If the stone is worn more than 1/8" I like to hit it with a sander, preferably a 6X48 or a 12" disc. Use quick pressing motions- press it somewhat firmly against the belt/disc for a second and a half, then pull it off and see how much more material you need to take off. I'm always paranoid I'll overheat a stone and crack it, but that has never happened. When the surface is flat I take it to a sheet of 100-240 grit sandpaper on a flat piece of wood or piece of marble I have and scrub until the scratches from the first sanding are mostly gone.

The best way I have found to clean glazed stones (best way ever!!...) is to sneak them into the dishwasher. Afterwards use ATF with or without some mineral spirits mixed in and they don't seem to glaze.

My method has much in common with several posts above...

Step 1. Belt sander, about 180 grit.

Step 2. Finish using wet and dry paper (grit depending on the stone in question) stuck on a flat piece of glass with a spray of water or oil (depending on if it is a Japanase type waterstone or like your India stone).

My piece of ca 10 x 14 inch half-inch plate glass with the edges rounded cost about 5 bucks at a glass place). Plate glass is REALLY flat (and cheap).

I like the idea above about using a diswasher to de-glaze a stone that is still flat! This will save me some workk in the future. Thanks Mark!

John