How Do You Flatten Aluminum Oxide Stones?

EngrSorenson

EngrSorenson

Noticed by Senpai
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I love my stones from FortyTwoBlades FortyTwoBlades , particularly my pocket stone which has now seen enough action to cup.
I've tried to do some research online, but it's surprisingly hard to find information which doesn't pertain to water stones.

So I'll just ask the folks here- How do you flatten your Aluminum Oxide Stones?
Cheap and easy would be my preference. One thing I love about the Baryonyx stones is that they're inexpensive.
 
You can do it with a regular old flattening stone. A lot of water stones are themelves a type of ceramic.. not exactly the same but ceramic nonetheless. I can't imagine it would work any different.

I would recommend an Atoma 140 grit diamond plate though if its not a fine stone.

If it's fine or ultra fine I'd get the Atoma 600.

They make fantastic flattening plates.
 
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I think many experts here have flattened/lapped their AlOx stones using coarse SiC grit on a flat & hard surface like glass or concrete. Something like 60-grit SiC has been recommended often for that sort of work. Pretty sure that method has been suggested for AlOx stones like Norton's India. On that note, I have a pocket-sized Norton Fine India that easily responded to some edge-radiusing I did for use on recurved edges, using the coarse side of an inexpensive SiC oil stone to do the shaping (like Norton's Economy stone in SiC, or one from Ace Hardware). See the pic below of the result. So, a simple coarse SiC stone might work for flattening them as well. Would probably be best to lubricate everything with oil or water before doing such grinding.
ZM6ApeM.jpg
 
These two methods work well too. Whatever method you choose just make sure surface you use actually is flat.. I've messed up in the past grinding my old stones on concrete and ended up with something off kilter. I only recommend atoma because it takes that step out. Their plates are the machined very flat.
 
Loose, coarse silicon carbide grit on a flat surface is recommended for flattening larger stones, as the loose grit works like little ball bearings to use pressure to break grit free, which is much faster than fixed abrasive is. A granite tile is often the cheapest way to get a durable flat surface. However, for small stones especially, I like using a cheap no-center-hole diamond lapidary disc off the 'bay. You can get small ones pretty cheap, but I always buy mine at 12" diameter because then it's big enough to lap bench stones for quick touchups.

While flatness is preferred, people tend to over-emphasize how necessary it is in your abrasive surface so long as it isn't way out of true. The nature of hand sharpening has much more impact on interface angle than very slight deviations in the stone surface will, and as soon as you start using a bonded stone it's at least a little out of flat. If perfection were required we never would have found knives useful. As I like to say, "Good enough is good enough; that's why it's called 'good enough.'" If the dishing is easily visible against a flat reference, it's time to flatten it, of course, but I wouldn't worry too hard about making sure it (and your lapping plate/surface) is perfect.
 
FortyTwoBlades said:
While flatness is preferred, people tend to over-emphasize how necessary it is in your abrasive surface so long as it isn't way out of true.
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I appreciate this advice; there’s a fine line between accuracy and wasting resources trying to achieve some impractical end.

I’ll look into SiC grit, and maybe experiment with SiC sandpaper.
 
You can rub two stones together or you can use an expendable sidewalk or concrete surface to get your stones pretty flat. Finish up with something more precise, if you wish.
 
You can get decent SiC flattening/lapping stones online pretty cheap (like $12) if you keep your eyes peeled.

I also recently picked up a 3" x 8" CKTG 140 grit diamond flattening plate (which does double-duty as a really coarse sharpener) for about $30.
 
So I have the silicone carbide grit! I got the course stuff.

I imagine I should do this flattening while the stone is wet?
 
Coarse means 60 grit? 80 grit? 120 grit? I am just curious, should not make much a difference.

You mix the loose silicone carbide powder with water. Some mark a grid on the stone with a pencil. This should work better if the stone is dry. But if the stone is still wet, it will work, too.
 
ARj1L08.jpeg

Thanks for all the help folks! The pencil lines came off everywhere, though I’m sure there’s a slight hollow in the center judging from the discoloration, but it wasn’t worth wasting more stone.

Love these pocket stones!
 
For a flat surface you can use a piece of glass. Or if you're really OCD, get a piece of float glass. I guess most window glass is float glass, actually.
 
Blade Lab said:
For a flat surface you can use a piece of glass. Or if you're really OCD, get a piece of float glass. I guess most window glass is float glass, actually.
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Most flat glass is made by the float process. It's an economical method of producing a perfectly flat surface (or at least as flat as a fluid can be on the Earth's surface.)

Glass does tend to wear quickly, so a polished granite flooring tile is a more wear-resistant alternative that can be obtained pretty economically.
 
FortyTwoBlades said:
Most flat glass is made by the float process. It's an economical method of producing a perfectly flat surface (or at least as flat as a fluid can be on the Earth's surface.)

Glass does tend to wear quickly, so a polished granite flooring tile is a more wear-resistant alternative that can be obtained pretty economically
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Again, being a bit anal, but I wouldn't trust that a spare piece of granite is going to be perfectly flat. I've had pieces of marble that weren't particularly close, for example.
 
Blade Lab said:
Again, being a bit anal, but I wouldn't trust that a spare piece of granite is going to be perfectly flat. I've had pieces of marble that weren't particularly close, for example.
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Agreed. None of the three 12" x 12" black granite tiles I have are reference flat, and they get less flat as I continue to grind on them. One of these days I mean to lap them against each other, which is why I have three, but I know it's going to be a slow job so I always put it off. It hasn't yet been a problem for stone flattening.
 
It’s impossible to determine how flat is flat enough, but I’m sure it doesn’t need to be the certified +/- 0.0005 of the DMT 95 lapping plate.
 
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