How to restore wetstone?

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Malty Falcon

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Jul 22, 2021
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https://imgur.com/a/o2ikwiX

I found a rather beefy wetstone in a restaurant cellar awhile back. I suspect the stone is from the 60's or maybe even older. I don't know why a wetstone would be so thick at only 6" long. Overall dimensions are 6" X 4" X 2" , and appears to be mostly flat and fine textured. Is there a certain kind of file required to flatten it, or can I use sandpaper on a flat surface? It seems like a soft stone, and I'm not even sure it will sharpen the supersteel knives i tend to carry.

What will the usefulness be with a soft, perhaps 1200 grit stone? Also, how do I determine if it really is a wetstone, or oiled stone?
Thank for any insight!
 
If it is a water stone I would pick up a 400/1000 diamond plate to flatten/clean it up. A diamond plate is a very convenient thing to have anyway and not very expensive.
 
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Some popular method to flatten whetstone are:
1. Use sandpaper on a flat surface, your kitchen countertop should be plenty flat
2. Use loose abrasives and a flat surface, usually on a dedicated glass plate because you'll scratch the plate also.
3. Use a coarse sharpening stone to flatten a sharpening stone, I am currently using this method and had had good results.
4. Stone flattener/fixer, either diamond plate or a dedicated stone fixer.

Whetstone can sharpen supersteel, I sharpen M390 with a King whetstone all the time, but there's a catch, using whetstone on higher grit on high vanadium carbide steel will yield inferior edge holding. The reason for this phenomenon is not yet understood, a common theory is "carbide tear out", but it's still an on going debate.

A good rule of thumb for sharpening super steel:
At 3-4% vanadium:
1. Sharpening at lower grit (under 1000) whetstone (Aluminum Oxide or Silicon Carbide) or diamond/CBN stone give similar results
2. Higher grit (over 1000), edges sharpened with whetstone will be inferior to sharpening with diamond/cbn stone (loose sharpness faster)
 
The word is "whetstone" and not "wetstone" and it applies to water stones and water stones. Whet means to sharpen.
Some stones can be used as either water stones or oil stones, like the Washita stones, novaculite, or India stones. Oil does help with the swarf though
Pour some water on it and see if it beads up. If it does and you'd like to use water instead, soak it in strong soap water.

One reason for such a thick stone is that it is soft and there are plenty of knives in restaurant.
 
The loose abrasive method is by far the fastest and most effective method in my experience. A glass "cutting board" or a granite floor tile can be used as the flat surface, and coarse black silicon carbide grit is the recommended loose grit.

There's lots of possible reasons it was made in the dimensions it was, not the least of which being that it may have originally been intended for some use other than knives.
 
Malty Falcon said:


What will the usefulness be with a soft, perhaps 1200 grit stone? Also, how do I determine if it really is a wetstone, or oiled stone?
Thank for any insight!
Click to expand...
Take a piece of window glass, the size of 4 squares of stone or more, the more - the more convenient, or a piece of glass mirror, mirrors are usually smoother than window panes, they are sometimes thrown in the trash, so you can get them for free. Next, you need to buy silicon carbide powder in several grains - 80, 150, 220, 400, 800. There is no point in using smaller grain.

And whether this stone is a synthetic water Japanese stone or an ordinary stone for using oil, this can already be said after you make it flat and beautiful :)

here is a great guide

A soft stone is quite useful, if the stone is soft and new layers of abrasive are exposed quickly, then this is good for sharpening very hard steels. My friend finishes sharpening hard wood chisels on similar soft stones (64-65 HRc). You just need to lead the chisel always forward with the striking part (if it is a knife, then forward with the spine) and carefully monitor the sharpening angle, and do not apply strong pressure.
 
Finishing is best performed on a very hard stone rather than a soft one. Soft is generally best for your intermediary sharpening since the loose grit that forms a slurry on the stone surface helps cut off any burr that develops. The downside is that it also tends to make getting a fully refined and crisp apex difficult.
 
Yes, I advised him to buy translucent Arkansas or something from Japanese stones for these purposes, but he is an adherent of using artificial silicon carbide stones and his soft stone is the finest that he could find.

I recently watched him work, he uses a rolling machine. Movement only in the direction of the arrow. Result out to be very sharp. Practically does not use pressure, no suspension, no lubrication, dry stone, about 20-30 movements to finish.

1635967571841.png
 
So I first used a coarse file, to try and remove grime, and not much shaping happened. Next I used 100 grit sandpaper on a marble tile. After 3-5 minutes, I got this:

I sprayed the whetstone with heavy duty degreaser, and continued for 15 more minutes, changing out the sandpaper when necessary. After awhile, I saw the flattened, high part of the stone was really polished, almost glazed or porcelain-like. Next image shows the stone after trying it out on my hard-to-sharpen Manix 2 with CPM S110V.
4gsAZhHm.jpg


Since I couldn't see distinct "beading" when I wetted (whetted?) the whetstone with water, I used it to sharpen my knife with water. I cannot tell if it is a "hard" or "soft" stone from just one use, but it took a long time to get it close to flat with 100 grit aluminum oxide sandpaper. What I can tell, though, is that it put a really keen edge on the S110V! This has been the hardest to sharpen knife that I own. I recently bought another Spyderco device, the Combo stone, and it helps A LOT for me, especially with M-4 and C20V. But the file grit of this antique stone will be fun to figure out. Thanks for the advice.
 
A file is just going to be ruined on a sharpening stone. Your stone is probably made of aluminum oxide, and you glazed it by using sandpaper of equal hardness and it's also why it took so long. The stone is now so fine because the knife is now mostly just gliding over it rather than being abraded. If using sandpaper on it (not a recommended method) you'd do better using silicon carbide. Silicon carbide is effective on silicon carbide stones using the loose grit method because it is functioning under 3-body abrasion rather than two-body like with sandpaper. A diamond plate can also be used, but will still be slower than the loose grit method and will put significant wear on the diamonds.
 
FortyTwoBlades FortyTwoBlades fully right, yes, there is also a problem with aluminum oxide stones, if you rub them with other aluminum oxide stones or sandpaper, then their surface layer is smoothed and, in fact, deteriorates, it really glides like on glass. It is best to use a piece of glass and silicon carbide powder. It's cheap and readily available. One thing is clear for sure, this is a hard stone. A soft stone, even on sandpaper, would give off a lot of powder / slurry. Today I was putting some very hard stones in order, silicon carbide is just a salvation.
 
That's literally what I was describing, yes. Abrasives of the same type rubbing against one another results in the grains being worn down and dulled, causing the stone to glaze.
 
Does silicon carbide come in various "grits"? Which should I use, or how do I determine which one will fix up this stone? I just read on Wikipedia that silicon carbide stones have been in use since 1893, so mine could be really vintage.

Even in its glazed state, it works to fine tune some edges. Now I really want to fix it properly. Thanks for the tricks.
 
You really don't want your stone glazed. It'll just rub the steel, pushing it back and forth instead of abrading it, and this induces fatigue at the apex, resulting in reduced edge retention. Your stone is not silicon carbide, as silicon carbide is either black or grey-green (referred to as "green" silicon carbide.) Yes, it comes in various grits, but also breaks down into finer grit quickly, so you'll generally do best with approximately 60 grit black silicon carbide.
 
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