Recommendation? Lapping/Preparing whetstone surface and grit contamination

[HyperXHyperX]

Hi everybody,

As always, I happen to be somewhat confused. I've got a couple Shapton Kuromaku whetstones and I've got the Atoma 140 in order to keep them flat. But is it enough to just lap them with the Atoma 140, or do I need to somehow "prepare" the surface, as the finish the 140 leaves feels kinda rough?

Some people recommend using an Atoma 400 for every stone that is above 400 grit. Some people say you can just rub two similar stones together (i.e. 8k and 5k or 2k and 1k), but isn't that a problem because of grit cross contamination? I read that you should thoroughly remove loose grit from stone, water, hands etc.

What's your method?

 

[311climber]

whoops dbl post

 

[311climber]

Hi everybody,

As always, I happen to be somewhat confused. I've got a couple Shapton Kuromaku whetstones and I've got the Atoma 140 in order to keep them flat. But is it enough to just lap them with the Atoma 140, or do I need to somehow "prepare" the surface, as the finish the 140 leaves feels kinda rough?

Some people recommend using an Atoma 400 for every stone that is above 400 grit. Some people say you can just rub two similar stones together (i.e. 8k and 5k or 2k and 1k), but isn't that a problem because of grit cross contamination? I read that you should thoroughly remove loose grit from stone, water, hands etc.

What's your method?

i never use my diamond plates on anything but steel, ymmv, but i usually see the stone flatten and watch the nickel plated diamonds start to haze and rip the diamonds from the plate. i use either my other kuromakus to flatten each other. the 120 can feel fairly flat as a flattening stone, and i used it to flatten my whole line of shaptons including the glass ones up to 12k. but of course the 12 was flattened last in sequence to keep it from being super aggressive. i def. wouldnt put a brand new 120 kuromaku to a 12k but after a few stones lower than 2k it works well for me up to the 12k. ive also used the gritomatic sic stones for flattening. alot of people like loose sic on plate glass or tile etc. i would def. use something that sheds grit to flatten something that sheds grit if that makes sense. sitting under a sink of running water you can make pretty quick work of it. i dont worry about cross contamination myself, besides on my strops. if it was under a facet running while flattening most grit runs off. now i cant say ive put my microscope to my 12k edge but it still puts a decent naked eye mirror and i definately didnt ever see 120 grit scratches. im sure it can embed into a stone but ive not seen a big problem and if others put an 8k to a 5k they must not be seeing 5k scratches in their 8k or you would probably hear how big of a no no it is. especially around here

 

[Stockman]

I use an Atoma 140 on my SP 220 and 320, the Atoma 400 on SP 1000, 2000 and 5000.
Seems to work well for me, keeps the stones flat without effecting the surface in any negative way.
The 220 and 320 need a bit more flattening as they are used for re profiling/setting edges if required, so they dish out a bit quicker, they are softer and I use a lot more pressure.

 

[3D Anvil]

I believe the rule of thumb for lapping is to use a grit that's about 1/3 the grit rating of the subject stone. It's okay to go lower, but I think it's a bad idea to go higher than that.

I use a piece of float glass with sic powders in various grits.

 

[catspa]

I don’t flatten my stones. If they dish out, I use them dished out.

Parker

 

[Albin]

I don’t flatten my stones. If they dish out, I use them dished out.

Parker

When I watched them sharpen my RMK #5-5 back in 1979 at the Randall shop, the stone the guy used had a very obvious swayback. Didn't seem to bother him and it sure didn't prevent the knife from being sharpened!

 

[3D Anvil]

As long as your blade doesn't have completely straight sections, flatness doesn't really matter. Otherwise ... it matters.

 

[HyperXHyperX]

i never use my diamond plates on anything but steel, ymmv, but i usually see the stone flatten and watch the nickel plated diamonds start to haze and rip the diamonds from the plate.

sitting under a sink of running water you can make pretty quick work of it. i dont worry about cross contamination myself, besides on my strops. if it was under a facet running while flattening most grit runs off.

I guess I worried too much about grit contamination, thanks. The way Shapton worded it in their FAQ it's supposed to be a huge deal. I will try flattening with diamond plates and if they die too quickly, I'll just use the stones then.

I use an Atoma 140 on my SP 220 and 320, the Atoma 400 on SP 1000, 2000 and 5000.
Seems to work well for me, keeps the stones flat without effecting the surface in any negative way.

Then I guess an Atoma 400 will be my next buy.

I believe the rule of thumb for lapping is to use a grit that's about 1/3 the grit rating of the subject stone. It's okay to go lower, but I think it's a bad idea to go higher than that.

That's interesting, because Shapton essentially says to rub similar (grit) stones against each other. Why do you think it is a bad idea exactly?

As long as your blade doesn't have completely straight sections, flatness doesn't really matter. Otherwise ... it matters.

Most of my blades don't. I do seem to get somewhat better results when they're flat, however. That being said, I still kinda suck. Yeah, I can get them to cut paper cleanly, but shaving hair on my arm? Nope...

 

[3D Anvil]

That's interesting, because Shapton essentially says to rub similar (grit) stones against each other. Why do you think it is a bad idea exactly?

I'm not totally sure, but my assumption is that:
1. Trying to flatten a stone with a similar-grit stone is a lot slower than using a coarser grit; and
2. The finer stone will make your coarser stone cut slower than it should until it eventually reverts to its natural texture.

If you don't want to use loose grit, another option is to use silicon carbide sandpaper on a flat surface.

 

[777 Edge]

If you only have the Atoma 140, you can make it work just fine. Flatten all your stones with the 140 first, and then just rub the Kuromaku stones together (1 grit apart) for a little while - under running water.

For example - after lapping all your Kuromaku stones with the Atoma 140, rub the Kuromaku 120&220 together, then rub the 320&1000 together, then 1500&2000; 5000&8000; 12000&30000...you get the idea - depending on which stones you have. Rinse them all properly after this and scrub a little bit with a toothbrush or something. The running water + proper rinsing and cleaning will prevent any cross contamination.

Even if you used the Atoma 140 alone and immediately started using the stones, it would only be the first few minutes of sharpening where they cut a little more aggressively due to the Atoma grooves cutting little high and low "hills and valleys" in the stones. After a short while, the tiny "valleys and hills" even out and the stones cut the way they are meant to again. Remember - its the abrasive in the stones that cut, not the bond of the Kuromaku stones so in reality it doesn't really matter in the long run how you lap them. It's just the first few minutes of sharpening (after lapping) that will be a little more agressive.