Preyda stones are not flat (flatten a fine stone??)

[Andrew Pitonyak]

Some years back I purchased a set of Preyda Arkansas stones for a friend but he never used them (or more accurately never had time for me to teach him to use them) so they sat in a box unused. I finally opened them and used them.

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For many reasons I really wanted to like this set of stones but I had trouble getting consistent results... And then I thought "is that corner low?" It turns out that two of the three stones are not flat. The finest stone, the "Black Hard" is out of flat on both sides. The stones are out of flat along both the length and the width, which means that it takes a lot of work for me to get results. The Soft stone is flat on one side, but not the other. The Hard stone is flat on both sides. If I had not figured this out years after purchase I would just take it back (WoodCraft has great support and a nice return policy). After a few years, it is on me for not checking.... But I have never checked a new stone for flat. On a whim, I went back and checked some of my other stones, which means that I checked about 35 stones. Every stone I could access (some are still shrink wrapped), was flat except for one heavily used Washita stone purchased off eBay. OK, many of my Washita stones were purchased off Ebay and I flattened the stone that was not flat. So all of my Norton, Best, and Dan's stones were all flat when purchased new.


Previously I have only checked used stones for flat. Two out of three stones out of flat. I do like the packaging and the form factor, something that is nice to keep at the office when I want to mindlessly do something while killing time.

I have only flattened Washita stones, never a Hard Black. I remember some advice related to Washita stones that recommended dressing the two primary sides with different grit Silicon Carbide crystals because the roughness affects the scratch patterns supposedly. I have never tested any of this, but i do have many different grits of Silicon Carbide crystals I can use. I expect that this would be rather pronounced with a "Hard Black" stone, which is pretty fine. Kind of a waste of time if I need to then polish the stone. I might do it just to do it, but how annoying.

I need to remove between 0.5 mm and 1 mm to flatten; closer to 1 mm.

I assume that most of you were smart enough to check your stones for flat.

[Cameron Wood]

I would use #120 wet/dry sandpaper on a flat surface, with water. Finish by lapping the stones against each other, also with water.

Some elbow grease, but not a big deal.

[Rafael Herrera]

I flatten washitas with 90x grit SiC powder and leave it at that. The same could be done with your soft ark.

Use a finer grit for the harder stones, but it may take more time to get them flat.

Use a fine grit to get the roughness out of the hard ones but not too much since you don't really want to polish them.

[les winter]

Dan's will flatten stones of any manufacturer for a modest price.

[Andrew Pitonyak]

Dan's will flatten stones of any manufacturer for a modest price.

Interesting, that had not occurred to me. I will admit, however, that I considered just replacing the out of flat stones with Dan's stones since I own a bunch of them, including some stones that are the same size. I considered building a similar box to house a set from either Dan's (most of my stones are from Dan's) or from Best (I have a few sets of different sizes).

I will do a bit of work and respond back.

[Rafael Herrera]

Dan's will flatten stones of any manufacturer for a modest price.

That doesn't make a lot of sense to me. If one has the lapping grit, the whole things takes about 15 minutes or less.

[les winter]

Depends how out of flat the stones are and how flat the substrate is. When I had the same issue, the cost of the flattening by Dan's was less than the postage. Nothing wrong with doing it yourself. In my case, after 1/2 hour of trying, I gave up.

[Rafael Herrera]

I don't know if you've ever tried silicon carbide grit, but before using that I saw recommendations to use sand paper, concrete blocks diamond stones, etc. I tried some of them, they all are orders of magnitude slower and ineffective compared to sic grit. It really doesn't take much on most stones: arks, washitas, indias, crystolons, slates, etc.

[Andrew Pitonyak]

I started with 80 grit

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After about 10 minutes, the soft stone was sufficiently flat that I called it good. You can see some progress with the 80 grit.

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Things were going so slowly that I switched to 45 grit. An hour later I simply gave up. Both sides are out of flat and it is still out of flat. I don't think that Preyda stones are not worth the trouble I think. I would want to flatten both sides and then polish both sides. Makes more sense for me to just deal with the stone from the 1/2" side and use it to sharpen knives with a concave type blade (or just throw it away).

Clearly I made some progress, but I am still out on both ends of the stone and I have not touched the other side.

Dan's rates their stones ass Medium (soft), Fine (Hard), Extra Fine (True Hard or Translucent), and Ultra Fine (Black).

In the 6x2x1/2 size I have a Medium, Fine, two Translucent stones, and (in theory) two Ultra Fine stones. I think that one of my Ultra Fine stones is with my chip Caving stones. My "Best" stones are mostly 10x3 and 8x2, and my other Dan's stones are mostly 8" x 3" and 10" x 3" stones. So if I want to keep a set in the existing packaging I could make that happen, or, I could just build another box.

In the meantime, I will likely just avoid Preyda stones in the future.

[Jim Koepke]

I also have one of the three stone sets from Woodcraft. They haven't seen much use in the past 20 years.

Dan's rates their stones ass Medium (soft), Fine (Hard), Extra Fine (True Hard or Translucent), and Ultra Fine (Black).

My Dan's stones are the same, though my translucent are slip stones and other small stones. The Medium (soft) is not as soft as I would have hoped. Some of my other stones were purchased as Washita stones or have a similar action to a Washita.

My Dan's Fine (Hard) and Ultra Fine (Black) Arkansas stones have been great in my switch to using mostly oilstones.

jtk

[Andrew Pitonyak]

I don't know if you've ever tried silicon carbide grit, but before using that I saw recommendations to use sand paper, concrete blocks diamond stones, etc. I tried some of them, they all are orders of magnitude slower and ineffective compared to sic grit. It really doesn't take much on most stones: arks, washitas, indias, crystolons, slates, etc.

Yeah, that is what I used. It was not working well with the Hard Black stone. I have only used it previously on Washita stones. It was fast for the Soft stone as well. Sadly, the Hard Black was the worst of the bunch. Also, the Hard stone is high in the middle, which (in my experience), is the most difficult to flatten (because the stone will rock),

[Andrew Pitonyak]

Jim,

Is your set of three flat? 2 out of 3 out of flat feels very bad. I sent an email to Preyda but they did not get back to me. When I had questions for Dan's, they were immediately responsive to my questions. Of course, I never had a problem with a stone from Dan's. They cost more but I perceive them as better than the rest, not that I am sufficiently good to know if this is correct.

I expect the same high quality from Norton (by the way). Not had any complaints about my stones from Best, but I use my Dan's stone more.

[Derek Cohen]

I flatten washitas with 90x grit SiC powder and leave it at that. The same could be done with your soft ark.

Use a finer grit for the harder stones, but it may take more time to get them flat.

Use a fine grit to get the roughness out of the hard ones but not too much since you don't really want to polish them.

Raf, I am not disputing what you do here, but have a question about the use of the finer grit …

It has long been a puzzle for me why some recommend coarse grits to flatten stones at the coarser end of the spectrum, and finer grits for stones at the finer end of the spectrum. The point is, as I believe, the result in honing comes from the grit in the stone and not the surface treatment of the stone.

I use the same coarser grit (140 diamond stone) to maintain all my waterstones. In the case of these oil stones I would use the 90 grit SIC powder or the diamond equivalent.

Regards from Perth

Derek

[Warren Mickley]

Raf, I am not disputing what you do here, but have a question about the use of the finer grit …

It has long been a puzzle for me why some recommend coarse grits to flatten stones at the coarser end of the spectrum, and finer grits for stones at the finer end of the spectrum. The point is, as I believe, the result in honing comes from the grit in the stone and not the surface treatment of the stone.

I use the same coarser grit (140 diamond stone) to maintain all my waterstones. In the case of these oil stones I would use the 90 grit SIC powder or the diamond equivalent.

I sounds like you have never learned to use an Arkansas stone. The finer stones have finer crevices. If you cut coarse crevices in a fine stone, the crevices will do the cutting and the stone will not polish as it should.

[Derek Cohen]

Warren, I have never used an Arkansas stone. Hence my question.

Regards from Perth

Derek