How NOT to flatten a Black Arkansas oil stone! Belt Sander...

[Nick Sorenson]

I have a black oil stone and decided to use a belt sander to flatten it (came from Hall's Pro Edge a few years back - before the new owner and was not flat). Anyways, I put it on my high speed 6x48 belt sander with 40 grit Aluminum Zirconia and kept it moving. It was pretty slow going believe it or not and the bad part... it took chips out of the stone in the center.

Well that said, I did find a better way to rough out a stone. My wet/dry grinder's slow wet wheel works pretty well.

The big problem with the Hall's stone is that they were Convex which means you have to make it a little concave before actually flattening or it'll just rock on the flat plate when sanding and remain convex instead of going flat.

That also said, I wonder if I could have just paid a willing machine shop with a blanchard grinder to flatten this thing in a few quick swipes...

[Tom M King]

I got a set of 10" stones from them two or three years ago that were pretty doggone flat, also before they sold the company.

[Nick Sorenson]

I got a set of 10" stones from them two or three years ago that were pretty doggone flat, also before they sold the company.

Mine were flat long ways but not side to side (had about 0.010" of an arch in the center).

[Tom M King]

I guess some of the equipment to slice and prep them had wear. I must have been lucky in the service life of the equipment. .01 is a lot. I remember when cars had points, and it was common to set them with a matchbook cover, which was .015, for those that can't visualize thicknesses by decimals.

[Nick Sorenson]

I guess some of the equipment to slice and prep them had wear. I must have been lucky in the service life of the equipment. .01 is a lot. I remember when cars had points, and it was common to set them with a matchbook cover, which was .015, for those that can't visualize thicknesses by decimals.

I still have a vintage zero turn mower that has points. Easy to start with a pull rope compared to EI.

As far as this stone being out, I didn't measure but I'd guess it's more than what I put. I rocked a 6" straight edge on the hump and there's probably .030 or .040 under the side opposite the one pushed all the way down. That means that it's at least .015" of a crown.

[Nick Sorenson]

Edit to my initial idea with the wet/dry grinder. The wet does work but it's tough to get dead center and not tilted. Any tilting leaves a deep mark from the edge of the wheel. Not good!

So far the only way I know of to level these is sandpaper on a flat plate (Glass or a tile). And any convex center has to be taken out first. I wish there was a faster way. I know the large belt sander wasn't friendly to mine.

[george wilson]

An old and effective way to flatten a black Arkansas(or other stone) is to lay a big sandstone grinding wheel on its side. Rub the stone on it with water. In a few minutes,I flattened a black Arkansas stone in the gunsmith's shop in Wmsbg. that way. I went in there,and one of the guys was trying to SAND a black stone with 600 wet or dry paper wrapped around a file. I told him that would take 200 years and showed him the old trick. He was glad to learn it.

[Malcolm Schweizer]

Do you think heat was the issue that caused the chipping? Maybe the stone heated in one place more than another and caused tiny stress fractures. Anyway, I never would have thought of any of the above methods. I would use a diamond flattening plate- this is not to say the other methods are wrong, just that I would not have thought of it.

[Steve Voigt]

Edit to my initial idea with the wet/dry grinder. The wet does work but it's tough to get dead center and not tilted. Any tilting leaves a deep mark from the edge of the wheel. Not good!

So far the only way I know of to level these is sandpaper on a flat plate (Glass or a tile). And any convex center has to be taken out first. I wish there was a faster way. I know the large belt sander wasn't friendly to mine.

Sandpaper is not a good way. Even the zirconium belts wear out very quickly. Get some loose 60-80 grit SC. You can get it for around $5 a pound on Ebay, and a pound or two will last many years. Sprinkle it on your glass plate, squirt with WD-40, and you'll be off to the races. (kills the glass plate for anything else, so don't use some super-nice thick piece. Get a piece of ordinary 1/4" glass and put it on a flat piece of mdf)

[Nick Sorenson]

Sandpaper is not a good way. Even the zirconium belts wear out very quickly. Get some loose 60-80 grit SC. You can get it for around $5 a pound on Ebay, and a pound or two will last many years. Sprinkle it on your glass plate, squirt with WD-40, and you'll be off to the races. (kills the glass plate for anything else, so don't use some super-nice thick piece. Get a piece of ordinary 1/4" glass and put it on a flat piece of mdf)

I wonder if Lowes granite tile (bought it for when I was using the ''scary sharp' method) would work? I notice that even it isn't completely flat but it's close. I have a few pieces of ceramic tile that's flatter.

ALSO: Malcolm, yes, I do think you're right in that the heat that was the problem.

[Jim Wheeler]

Sandpaper is not a good way. Even the zirconium belts wear out very quickly. Get some loose 60-80 grit SC. You can get it for around $5 a pound on Ebay, and a pound or two will last many years. Sprinkle it on your glass plate, squirt with WD-40, and you'll be off to the races. (kills the glass plate for anything else, so don't use some super-nice thick piece. Get a piece of ordinary 1/4" glass and put it on a flat piece of mdf)

That's the way I've always flattened and/or reconditioned stones, except I use water instead of WD-40. It works faster on some kinds of stones than on others. Even with 80 grit silicon carbide grit it took me nearly half a day to flatten a new surgical hard black Arkansas. Other kinds of stones didn't take nearly as long. Ordinary sand -even from your yard - will sometimes work to flatten stones, too, but not a hard black.

Jim

He who welds steel with flaming pine cones may accomplish anything!​

[Steve Voigt]

I wonder if Lowes granite tile (bought it for when I was using the ''scary sharp' method) would work?

No. The substrate has to be softer than what you're abrading. Get some glass, or you can just waste more time trying creative solutions if you want.