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flattening stones

Wed Aug 08, 2012 6:50 pm

140 grit diamond...inexpensive...is it ok?

dmt xxc seems to be everyones favorite but may not be good for high grit stones.

why not dmt xc...maybe you can use it for higher grit stones? Maybe this is a reason the cheaper stone is better?

whatt about flattening with a nubotuma 150? Any reason not to?



Re: flattening stones

Wed Aug 08, 2012 10:08 pm

Well it depends on how much flattening you need and what grit you are flattening.

My favorite is the Atoma, being a long time DMT user. Atomas are more expensive but IMO work best as a flattener and also work better on metal.

Now if you have a pretty well flattened stone and just need to flatten your stone just a bit more and it is a high grit stone, the XC or Atoma 400 is an excellent choice and leaves a better finish. I wouldn't recommend the XC for coarse stones.

So this leaves the XXC and 140 Atoma as the more universal stone flatteners and the other finer grits as a bit more narrow in range.

Some stones benefit from a coarser finish, especially coarse stones. A 220 GlassStone isn't very aggressive flattened with a finer plate - flatten it with the XXC or Atoma 140 and it takes on a much more aggressive character.

I wouldn't recommend flattening with a 150 Nubatama. The finish is too smooth. Just the wrong tool for the job. If you want to flatten with a stone, the 60 or 24 grit Nubatama Artae is more suitable. In general I don't like flattening stones with stones short of 60 or 24 grit stones. I also find that diamonds of appropriate grit flatten any stone whereas stones don't work so well on certain other stones Shaptons in particular (IMO). Shaptons and other harder stones just don't abrade well against other stones. I don't consider it a disadvantage as I pretty much flatten exclusively with diamond lapping plates.

I'm also fussy about grit crosscontamination between stones. I soak stones separately and don't put stones in a common bucket. You do see this practice commonly but I don't do it.

Now after flattening lets say a badly dished 5k or 8k stone, the surface texture may be a bit rough and you my want to texturize the surface, giving you more surface area and a better feel to the stone's surface. For this task a 1200 grit diamond stone is a real nice alternative and you can use a smaller 2x3" piece rather than a whole plate (These Atoma 1200 pieces mounted on a piece of granite are available at CKTG).


Re: flattening stones

Fri Aug 10, 2012 2:57 am

There is no reason not use a coarse flattener on a high grit stone except that it can make the stone feel really different. And natural stones behave entirely differently, because they are so hard and rely on how they break down to perform properly.

Also be careful when flattening stones with a diamond plate when it is new. There will be some diamond grit coming loose and it will leave ugly scratches on your knife and might even dent the edge a little. Gotta break em in, then it's hunky dory.

I got a 1200 grit diamond fold-up keychain thingy and snapped it off the keychain, so it's like a 1200 grit diamond fingerstone. I use it to dress my Rika 5k, build slurry, and I'm playing with it on the naturals.

And as far as a cheaper plate being BETTER...well I don't know about better, but I don't know why the DMTs are so popular in the 8" length other than they fit better in stone holders without adjustment. the 6" plates are much cheaper and will sharpen and flatten just the same. I only think you need the bigger ones if you are sharpening a lot or your are just an enthusiast.

Re: flattening stones

Fri Aug 10, 2012 5:03 am

Well not exactly. Natural stones span a very wide range of hardnesses, both in the awasedo and nakado. The reason you might not choose to use a very coarse diamond plate is to not waste precious stone and give a coarse surface to the stone. Pretty much a parallel argument as to why you might not want to start every sharpening job with a very coarse stone.

When generating mud on a stone for the purpose of sharpening as opposed to flattening, the coarseness of the mud is markedly affected by the coarseness of the diamond used to generate it and to some extent the surface texture. What you don't want particularly on a harder natural stone such as an Ozuku Asagi is to use a coarse diamond plate as this produces gouged out coarse particles many times coarser than the slurry that a finer plate would produce. Stone surface texture also allows for coarser particle generation as well as a different 'feel' than the stone is capable of providing. For an even finer grade of slurry, using a tomonagura is far better than slurry generation using a diamond plate.

Diamond plates do require a breakin. Cheaper plates will continue to shed diamonds, whereas the better plates will initially shed and then shed quite slowly.

For slurry generation, a smaller plate will do, but for flattening a plate as large or larger than the stone being flattened will assure a properly flattened coplanar surface. Basic geometry.

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