24, 46, and 80 grit sharpening stones

[Tom M King]

These Carborundum stones are not sold as sharpening stones, but rather as "rub bricks" for tile work. They're intended to be used to smooth down cut edges of tile.


I bought them a good while back to try out as sharpening stones for when I didn't have a grinder handy.


This afternoon, I sharpened four chisels that had some damage to their edges. I hadn't realized until I started to use it that my CBN wheel was worn to the point that it wouldn't put a pretty, straight grind on anything, so I drug these stones out.


They worked better than I thought they might. It wasn't really much slower than using a grinder. I don't think you want to skip grits though. At first I tried putting oil in them, but it would probably have taken a quart to saturate them, so I took them out to use a water hose, which worked fine.


The 24 and 46 stones are a little smaller than I like, but they worked okay. The foot long 80 grit's size is really nice.


I finished the chisels on my oil stones because I don't have my sharpening sink set up here. The edge of that chisel in the picture looks like it's really screwed up if you zoom in, but that's a Big Honking wavy wire edge!!! It cleaned right up starting on the purplish Washita stone.


I wish they made a 24 grit wheel for my mower blade sharpener. That thing Eats metal.

Here's a link to one of them: https://www.amazon.com/14-295-Setters-Black-Silicone-Carbide/dp/B00BC2HIAA/ref=sr_1_34?crid=RTHVMKX62KU&keywords=tile+rub+blo ck&qid=1679607494&sprefix=tile+rub+block%2Caps%2C9 8&sr=8-34

[Jack Dover]

My experience with coarse grit carborundum stones it that they cut fast while new, but then glaze over. And then it depends on a binder: if it's too hard, it won't release and new grit is not exposed. Seems to be the case with broken grinder wheels often used for hand sharpening. Or it's soft, but uneven and the stone goes out of flat and flattening it back is a pain, because there's still hard areas and they do quite a number on anything I have for flattening.

I have a "foot long" carborundum stone from Sharpening supplies. It feels like it's "case hardened" - worked through hard external layer, so there's a soft spot that dished quickly. So recently I've got 60/90 tumbling powder assuming I'll just use the stone as a base for free abrasive. And something interesting happened: I had to sprinkle the powder two or three times when it stopped cutting, but after that it's been 6 months and hard areas still cut. Saturation, I guess? But yeah, 60 or even 80 grit is definitely aggressive enough to be a viable alternative to power grinding. They would shoot sparks even.

I wonder how these stones behave with time? They're tile rubbing bricks, so I assume they're hard throughout?

[Mel Fulks]

Depends on the brand. Right now I can’t bring up the good one. Avoid the $1.00 brand new …on store junk table type.

[Tom M King]

I know the small ones are Kraft Tool brand, which is a good masonry tool name. The four chisels today didn't do anything to them that I can see. I kept the water running to wash away any swarf instantly. They still look like they did when I started with them.

When I went to get that Amazon link, it said I bought them Dec. 2021. Today was the first time I needed them. I looked for a link to the 80 grit one, but can't find where that one came from, and I don't remember.

I first tried starting with the 80 grit, but it was way too slow. The chisels had all found nails, so had some chunks out of their edges. The 24 grit rubs metal away like a steel loader bucket edge rubbing on the road. I quit using my loader to remove snow from the road because of the severe wear.

[Richard Coers]

You must really stroke it fast on the stone that it will cut nearly as fast as something going 1725rpm

[Luke Dupont]

I need me some of these!

I have a really nice looking firmer chisel that came in a batch of chisels on ebay, which I can only theorize was "worked on" by someone who should never ever be allowed near a grinder. There's like 1/4" of material that needs to be removed now...

[Tom M King]

I don't think I'd want to remove a 1/4" with these. These had small chunks missing, but probably not even 1/32 needed to be removed.

If I had a 24 grit wheel on a grinder I'm sure it would have been probably almost instantly done. The trouble is you need the 46 and 80 to get the deep scratches out.

These were carpentry chisels, and ones working on furniture never see damage like this. These will be kept in my truck with the oil stones for when a grinder is not convenient.
New CBN wheel ordered for the grinder, but this time no radiused edges.

[Jack Dover]

For an occasional heavy removal you can totally just get a 60-80grit sanding belt, but you probably would need a sharpening guide. Removing 1/4" is quite possible, just going to take you about an hour, so maybe work on a couple of chisels in one session, that will be a bit faster. The only issue with these stones in length, the link says they're 6" long, so realistically your working area will be about 3" long. A belt would give at least 36", and longer strokes mean more efficient removal. These stones are good in a traveling box to remove an occasional nick after hitting a nail or something. And the coarsest stone is listed at 34$ - I think you've mentioned you're in Japan? They have this big gray waterstone that is also very aggressive and used to cost somewhere around 25$. Not that 10$ really matter, it's just it's probably better to have a multipurpose stone when a space is limited. But I'd go with a belt for such a task.

[Steve Jenkins]

When I was a kid Dad had to cut and patch our concrete floor in a couple places. To smooth the areas after drying he gave me a carborundum block about the size of a brick and showed me how to get on my knees and holding the brick with both hands grind the concrete smooth. Because of the position on my knees leaning forward,stretching out and pulling back the block was called a “holy stone”. What memories.