Lapping Plates and stones

[Dale Coons]

Wow--passion runs high on this topic!

That's exactly what I use to flatten the Glasstones I still have in rotation (and oilstones, and the backs of several old paring chisels, and anything else that needs it).

The Dia-flat will work fine on Glass Stones.

....and Chris Shwarz' "Yee-Haw!" endorsement (which now that I re-read seems to cover just about any kind of stone there is)

I appreciate all the posts about different flattening options--they certainly give food for thought. I tried to be very specific in my original post. The DIA-FLAT lapping plate is not the same as any other DIA-(insert product name here). Basically what you all seem to be saying is I can stick with the Dia-Flat and it will work with anything I'm likely to get, be it ceramic, glass or just the plain old nortons I have. If I was in the market for another flattening option I'd give this perhaps more thought. Anybody disagree with that assessment?

[Jay Maiers]

Question for the masses about lapping plate flatness:
How flat do they need to be? +-.001 over the length? .002?

I just bought a DuoSharp and I'm not impressed by the flatness. Placed concave side down on a granite surface plate, I can easily slide a .004 shim under the center of the stone. I'm pretty sure that's not up to their specs, but I can't find a specific number or spec for these anywhere on the DMT site. In any case, I'm going to call them tomorrow and see what's what; I just wanted to get some opinions from y'all.

[David Weaver]

Flat enough that you can sharpen an iron or chisel and have no adverse issues (particularly with preparing the back of an iron or chisel).

It's hard to say how much that is.

However, I have not seen a duosharp that far out of flat. I think their guarantee may be .005" or something along those lines, but if you bought it at a retailer that has a good return policy, you can get them to take it back.

I'd just go order another of the same. It's unlikely it will be as far out of flat...or measurably out of flat at all.

[David Keller NC]

I for one will never return to the SiC paper on granite to flatten my stones. Not sure how you pulled it off but my paper would never come close to lasting that long before replacing. Must be due to the fact I wasn't using nortons, started that proccess with Naniwa SS's.

Yeah, I think that's a good explanation. According to Stu's site, the Naniwa SSs are ceramic, as are the Shaptons. Ceramic (typically Zirconium Oxide) is far harder than the typical SiO abrasive and clay-type binders that would be present in a natural waterstone or a man-made copy such as a King or a Norton. My guess (though I haven't looked it up) is that the Si-C abrasive in wet-dry paper is not as hard as the abrasive in a man-made ceramic stone, so you'd essentially be flattening the paper instead of the stone.

[Jay Maiers]

Flat enough that you can sharpen an iron or chisel and have no adverse issues (particularly with preparing the back of an iron or chisel).

It's hard to say how much that is.

However, I have not seen a duosharp that far out of flat. I think their guarantee may be .005" or something along those lines, but if you bought it at a retailer that has a good return policy, you can get them to take it back.

I'd just go order another of the same. It's unlikely it will be as far out of flat...or measurably out of flat at all.

Therein lies the problem. I have no experience with diamond plates for flattening stones, and have no idea if this is good enough or not. To date, my stone flattening has all been done on the granite surface plate with sandpaper. It works fine with the King stones I'm using, but I hate pulling the stone out of the holder and making a second (huge) mess in order to keep things flat.

The good news is that Amazon is the seller, so there will be no problem returning it if DMT says it's within spec.

[David Weaver]

if it's out .004 and you got it from amazon, exchange it. the next one will be better unless something has changed for the worse at DMT.

[John Coloccia]

My duos are dead flat.

[Stuart Tierney]

Yeah, I think that's a good explanation. According to Stu's site, the Naniwa SSs are ceramic, as are the Shaptons. Ceramic (typically Zirconium Oxide) is far harder than the typical SiO abrasive and clay-type binders that would be present in a natural waterstone or a man-made copy such as a King or a Norton. My guess (though I haven't looked it up) is that the Si-C abrasive in wet-dry paper is not as hard as the abrasive in a man-made ceramic stone, so you'd essentially be flattening the paper instead of the stone.

Not quite.

I call them 'ceramic' because that's what the folks who make them call them.

In actuality, the abrasive is ceramic, which is most commonly AlOx, not as hard as SiC in the W&D paper, but tougher. Stones like Shapton and the Naniwa SS use a resin (or plastic) binder, Sigma ceramic, Bester, some King, Suehiro and a few other use a proper 'ceramic' binder that's pressed into a shape and fired at very high temperature so the binder fuses into a solid mass. There's also magnesia binder, similar to vitrified ceramic, but is hard but brittle (Chosera) and sintered (Sigma Select II) where the SiC abrasive is fired at high temperature and pressure (don't ask exactly how) so the abrasive fuses to itself.

King and Norton and 'old school' type stones (many, generally soft) use a clay type binder which is softer and more readily friable (breaks down).

The problem isn't the abrasive, it's the binder. Softer stones can be flattened with SiC W&D paper because the stone's binder is less durable, and anything that gets lodged in the stone from the paper can also be easily dislodged. The soft paper back on the W&D tends to 'hold' any dislodged particles from the paper which may drive them into the stone. As mentioned, not a really big problem on soft stones.

On harder stone with a more durable binder, the chance of driving a particle of SiC from the paper is reduced, but if it does happen, then it's more likely to stay there and cause problems when you sharpen. Again, the paper backing prevents the particle from rolling and increases the chance of the particle becoming lodged in the stone. It's likely enough that very, very few 'ceramic' stones are suggested to be flattened with sandpaper, and of those that are, they're generally very coarse stones where the sandpaper grit is close to the stone's grit and won't be noticed.

When using loose grit on a hard surface you don't use much pressure to flatten, so the grit is unlikely to catch on the hard base and if by chance it is driven into the stone, it's likely to be dislodged by the other rolling grit particles, so doesn't pose a problem.

Using a diamond plate, the diamonds are held strongly to the plate, and any that do happen to become dislodged are between the stone and a coated, hard surface and are unlikely to lodge in the stone, or if they are, will likely become dislodged by other, still fixed, diamonds.

Sounds all kinds of odd perhaps, but that's what I've kind of worked out why paper is not a good idea for harder stones or those with durable binders, but ok for softer stones. I've done a little testing, and the results are inconclusive at the moment. I don't believe I'll have my opinion changed though, nor will I be recommending sandpaper as "a good idea".

And one should always flatten stones just before they're used and in the condition they're to be used in, i.e; soaked or damp. In that situation, the paper will also be wetted and more likely to become less than completely durable. If you're not flattening your stones in 'ready to use condition' then there's a genuine possibility that you're not actually flattening them at all, since some stones do change shape when wetted.


Dale, You've got the thing already, use it! No need for anything else until what you've got is worn out.

Jay, the thing should be 'flat'. There's no standard per se, but if you stick a good straight edge across it and the slip of light is not consistent at any point, it's not flat and should be returned/replaced. Light will come through between the plate and straight edge because it's covered in diamonds and not smooth, but the light should look the same for the full length, width and corner to corner.

Good luck out there.

Stu.

[David Keller NC]

Stuart - Interesting. I looked up several definitions of "ceramic", and it would seem that the generally accepted definition has more to do with the process by which the object is made (i.e., vitrified at high temperatures and/or pressures) than it does the precise composition. However, one could easily add that a true ceramic is composed of various mixtures of metallic or semi-metallic oxides (that last case takes care of "SiO2", or quartz) rather than (reduced) metallic compounds.

Your post does remind those that are cleaning/rehabbing old stones to never use a highly alkaline cleaner on them, at least in a soaking fashion. Alumina (AlOx), Silica (SiO2), Magnesia (MgOx and MgOH2), and several zirconium compounds are soluble in an alkaline aqueous solution. Many, many household cleaners are quite alkaline, including soap scum removers, drain cleaners, household ammonia, etc... Depending on contact time, one might just remove the top surface of the stone, or might eat away a big proportion of the whole thing.

I should mention to those who would like to try the SiC-on-a-granite-plate as an interim method before spending a large amount of $ on a diamond plate that there are some particulars to my method that might matter according to Stu's post:

1) I don't really use sandpaper in the sense of "paper". The material I use is Klingspor's non-woven fabric-like silicon carbide wet-dry "sandpaper" in 220 grit.

2) I soak all stones (waterstones, anyway) for a minimum of 20 minutes in clean tap water before flattening or using for sharpening. I also soak the paper - doing so hydrates the backing, and allows it to stick very firmly to a granite surface plate.

3) A new piece of SiC wet-dry needs to be "broken in" in that all areas of the paper need approximately the same contact with the stone. Otherwise, you wind up with sharp abrasive on the edges of the paper and not-so-sharp abrasive in the middle. The result is a convex stone - DAMHIKT. This is one reason you want your surface palte to be larger than the sandpaper.

4) Apply almost no pressure to the stone - just enough to move it back and forth and up and down, hold the stone in the middle, and flip it in your grip a few times during the flattening session. Low pressure, changing your grip, and covering the complete area of the sandpaper gives you a very high probability of a very flat result, at least if your surface plate that the sandpaper is bedded on is flat.

5) I frequently rinse the sandpaper/stone I'm flattening under clean running tapwater.

6) Using a coarse grit like 220 seems to have no adverse effects on high-grit-number stones (like 8000's). The surface it leaves is very smooth.

7) Using the afore-mentioned brand/type of paper, I've never had any issues with any grit embedding into my finer Norton/King waterstones, at least that was detectable on the steel surface I was polishing. That said, that may be more of a function of the way I sharpen - at the kitchen sink with running water close at hand to rinse stone/paper. My guess is that you might have issues if you use a washtub in your shop where mixed grits of water stone and wet/dry paper form a sludge that gets stirred up when you rinse your stones.

8) If you're using the kitchen sink, pouring gel-type Drano or the equivalent highly alkaline cleaner down the drain and allowing it to stand overnight before flushing will keep your traps/pipes clear of waterstone mud. I've verified this by taking the drain apart. Not sure what it might do to a septic system and filed lines, however.

One rather interesting idea that's an ancillary to this thread is the possibility of using Lee-Valley's diamond film for waterstone flattening. The potential advantage is faster cutting of harder stones, and matching the diamond grit to the grit of the stone so that a loose diamond or two that gets embedded doesn't matter all that much.

[Eddie Darby]

The lapping plate is suppose to be +/- 0.0005" or as we say, 'half a thou'.
Trend Diamond plates are the same when it comes to flatness.

The flatter the waterstones surface, the better when you are trying to attain sharpness, defined by 2 flat surfaces meeting together, without any reflection of light.

I have a piece of planed walnut, that came off a plane blade honed by one of the sharpening Guru's, that is extremely smooth, and when I sharpen I try to get the same smoothness.
So far it's still a challenge, but having a flat waterstone has helped a great deal in the process.