Creating natural sharpening stones from local rocks

S

Skane24

Joined
Jul 31, 2019
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Hello, was wondering if anyone else here has tried this, I have a good bit of sandstone on my property in my creek, and unfortunately at the moment don't have a tile saw, but I do have an angle grinder with some diamond masonry blades.

Has anyone else tried this before or had any success? I've found a pretty damn flat piece of sandstone and I think I'm gonna give it a try tomorrow.

I'm in MO, so not sure what other stones would be suitable for the task, sandstone was the first one to come to mind. Got any recommendations for some others?
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FortyTwoBlades said:
an only be reliably used on plain carbon steels. Anything with so much as chromium carbides tend to shrug off natural stones.
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That's been my issue with getting any more natural stones. Many beautiful ones with history. A lot fine quartz deposits. But even though I don't target super steels, my percentage of knives that can be actually sharpened with them is small. They aren't all 1095 and white paper steel.
 
It can be challenging to find a coarse natural grinding stone that'll actually work well for removing much metal from most any stainless blade these days. I live in New Mexico - there's sandstone all over the place here. But most every piece I've tried tends to do more damage to a stainless blade (even simple 420HC) than actually cutting the steel. Mostly it's just heavy blunting & burring issues, while not removing much steel at all. Only once have I managed to find a small piece of what I'd call 'siltstone' that worked relatively OK with a Case stainless blade I tried on it. It looked essentially like sandstone, but with much finer grit. I imagined it coming from a stream or lake bed, like fine, muddy silt eventually bonding together over time. When used with water, it worked up a slurry of loosely-bound fine grit that performed like a waterstone. It reground a functionally useful edge on the Case stainless (420HC) blade. But it was a small piece. So, with little use, it diminished pretty fast and became too thin & too fragile to be useful anymore. I've never found a larger piece like it since then.

A very smooth, fine-grained natural stone can work pretty well as a burnisher / polisher and for deburring purposes though.
 
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I have some black siltstone near me that makes for a stone suitable for razor finishing and I've made a decent number of stones from it but I rarely use them since I have sintered silicon carbide plates that do the same thing and work on steels with chromium carbides in 'em.
 
I found a piece of compressed sandstone this past week while on a trip to NC. Pulled it out of Johnson Creek. It is surprisingly flat, although I did take a concret block to it, also pulled from the creek. Playing around with it and just some mild steel, it feels like around an 800-1200 grit. Can't wait to see what it's like once I get home and get it lapped flat, and test out some blade steel.


https://photos.app.goo.gl/b9dhE8sz6bm6GuGV9
 
I found a piece of compressed sandstone this past week while on a trip to NC. Pulled it out of Johnson Creek. It is surprisingly flat, although I did take a concret block to it, also pulled from the creek. Playing around with it and just some mild steel, it feels like around an 800-1200 grit. Can't wait to see what it's like once I get home and get it lapped flat, and test out some blade steel.
 
Coarse naturals that perform close to man made stones don't exist, no reason not to use them if it you enjoy the process though.
Use plenty of water or oil, they seem to cut better and it prevents the surface from glazing.
 
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