Thread: Naniwa Superstone Lapping Issue

I was an early convert to the Naniwa Superstones and got them shortly after Lynn first described them on the forum. I've had a concern about them all along but here I am finally asking about it.

Normally, wear on a hone occurs in the middle, and the very ends of the hone, which get little blade contact, should be the highest regions of the hone after much use. Thus, when you draw gridlines on a hone, lapping should remove the grids from the ends first. The middle of the hone would be expected to be the lowest and so the gridlines should be removed from that region last.

Some of my Naniwas do not adhere to that expectation.

Despite using them extensively, and therefore expecting them to be worn primarily in the middle, whenever I lap some of my Naniwa hones most of the removal from the hone is in the middle. When I draw gridlines on the hones and lap them, the grids are first removed from the center. That means the middle region of the hone that is used the most seems to be getting thicker rather than thinner!



This occurs on the 2k, 3k, 8k, 10k, and 12k. It does not happen with the 200, 400, 1k, and 5k. These latter hones behave as one would expect and are lower in the center after use and so retain their gridlines in the middle longer during lapping. It seems to also occur with the Shapton Professional 1k. I also lapped and photographed the Naniwa Chosera 600 and 800 that I only recently started using, but I realized I don't recall if I lapped them flat before I started using them so I will reserve judgement on them for now.

Below I have shown photos of my hones in the intermediate stage of lapping. I took the 1k too far and removed all of the grids but it did look like the blue 5k at one point while I was lapping it.

If I attach these in proper order, the first photo is of the whole spectrum of hones with the 200 on the far left and the 12 on the far right.

The next photo will be of the Naniwa 200 and 400 and the Chosera 600 and 800.
Next is the Chosera 600 and 800, Shapton Professional 1k, and Naniwa 1k.
Next is Naniwa 1k, 2k, 3k, and 5k.
Last is Naniwa 5k, 8k, 10k, and 12k.

So, has anyone else experienced this? What I really want to know is if anyone can explain this?

I also have noticed weird patterns when lapping my Naniwas. As much as I like them when I am using them, I make sure to lap them before each use.

My guess is that whatever they use as a binder changes volume with water/temperature or something...

Originally Posted by BKratchmer

I also have noticed weird patterns when lapping my Naniwas. As much as I like them when I am using them, I make sure to lap them before each use.

My guess is that whatever they use as a binder changes volume with water/temperature or something...

I've assumed that as well, but it is odd that it would vary along the length of the hone and that it would not be consistent among all the hones.

Originally Posted by Utopian

I've assumed that as well, but it is odd that it would vary along the length of the hone and that it would not be consistent among all the hones.

I wonder if it has to do with warping or torsion-- only the top "layer" of the stone gets wet, and as it swells it warps the stone... the inconsistencies come from how well or where the stone is glued down... maybe?

Originally Posted by BKratchmer

I wonder if it has to do with warping or torsion-- only the top "layer" of the stone gets wet, and as it swells it warps the stone... the inconsistencies come from how well or where the stone is glued down... maybe?

I've considered that too, but I cannot imagine that they would be so haphazard with their gluing.

I guess I'll have to buy a set of the unmounted superstones to see how they behave!

One oddity that I failed to mention in the original post is that the Shapton Professional 1k does the same thing and it is not mounted. I borrowed JimmyHAD's full set of Professional last year but I only lightly touched them up and did not draw gridlines. Hopefully he will read this and comment on his experience with them.

You didn't say what you use for lapping, but I assume it's one or more of the DMT plates. If so, these are not much larger than the stones you're lapping, so you'll inevitably have some parts of the stone (the middle, say) spending more time on the DMT than others (the ends, say). That might account for the pattern you observe.

I lap on either a 9" x 12" Naniwa flattener or a granite plate with wet/dry. In both cases, all areas of the stone are in constant contact with the lapping medium. My stones all lap as one would expect, from the edges in. I have superstones, choseras, naturals, Bester, Suehiro Rika, Takenoko, Kitayama, and others; they all behave the same.

This explanation is reaching, I know, but if you can get hold of a granite plate I think it would be a great test.

My unmounted naniwas act the same way
Also seems to me that more water i add worse it gets

the super stones are resin bound and tend to bow, so that the the edges are high or the middle is high.
The direction of the bow can also change with time as you guys have experienced.

Even the ones mounted on a base are not mounted with more than a few drops of glue (I took my 1k apart when I switched to chosera).
I solved the bowing problem with my 10k SS by gluing it to the back of a worn off DMT, I used double sided carpenter's tape.

I think it is an interaction with the hone and the
plastic holder. The holder holds water and
the hone changes dimensions around the edges
and a little bit under the hone depending on the
glue job.

Try storing the hone inverted on paper or shop towels
so it drains and drys then just spray the surface.
Since you have lapped it once it is close enough to
just lap it enough to raise a slurry from now on.

ymmv

Originally Posted by wsfarrell

You didn't say what you use for lapping, but I assume it's one or more of the DMT plates. If so, these are not much larger than the stones you're lapping, so you'll inevitably have some parts of the stone (the middle, say) spending more time on the DMT than others (the ends, say). That might account for the pattern you observe.

I lap on either a 9" x 12" Naniwa flattener or a granite plate with wet/dry. In both cases, all areas of the stone are in constant contact with the lapping medium. My stones all lap as one would expect, from the edges in. I have superstones, choseras, naturals, Bester, Suehiro Rika, Takenoko, Kitayama, and others; they all behave the same.

This explanation is reaching, I know, but if you can get hold of a granite plate I think it would be a great test.

Thank you for your observation, but I have considered that and don't believe it to be the issue. I say this for two reasons.

First, I lap them on a Shapton DGLP (which measures 9.75" by 3" while the Naniwas are 8.25" by 2.75") and I am diligent about doing very small figure-8s and circles so that very little of the hone comes off the plate. Obviously some regions of the hone come off slightly but that cannot account for the lapping pattern.

Second, and most critically, if this were the issue, then all of my Naniwas would show the same effect, but they don't. The 200, 400, 1k, and 5k each exhibit the normally expected lapping pattern. If the size of the plate caused this, then the lapping pattern would be the same on all of the hones.