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Blade road flattener?

Sun Aug 05, 2012 12:26 pm

I'm looking for a coarse stone to flatten and remove scratches from the factory on the blade roads, thin blades, etc. I have diamonds from 220-600 and stones from there, so I need something a bit coarser so I don't spend all day thinning on a finer stone.

These are what I am considering:
Atoma 140x:


Shapton 120 Glass stone:

Shapton Pro 220x:

Nubatama Bamboo 150x:

Nubatama Ume 60 Grit:

Nubatama Ume 120 Grit:

Any thoughts??

Re: Blade road flattener?

Sun Aug 05, 2012 1:22 pm

The 2 I love most are the Glass 220 and Shapton Pro 320, but since it's so close to your diamond plates, I'd suggest the Glass 120, atoma 140 or Ume 120.

Re: Blade road flattener?

Sun Aug 05, 2012 3:47 pm

Specifically for removing scratches from factory grinds the Atoma 140 and DMT XXC will give you more scratches than they take away. The 120 glass would work but is thin and wears quickly. The 220 pro is a decent choice, but the 150 Nubatama is more aggressive and would be preferred. The Nubatama 60 grit is too aggresive for this task. If you need this you have some seriously rough knives. The Nubatama 120 grit is also a good choice with significantly more stone than the 120 Glass. My vote would go to the 150 Nubatama, which is both aggressive and leaves a very nice finish at the same time - exactly what you sound like what you are looking for. It's also worth noting that even going from a 140 Atoma scratch pattern to a 150 Nubatama pattern yields a significantly smoother finish.

Please review the recently listed 140 Atoma plus 150 Nubatama videos, particularly the Second video to see the scratch patterns produced from the Atoma and 150 bamboo. Hope this helps.


Re: Blade road flattener?

Sun Aug 05, 2012 4:42 pm

IME there is no quick way around this. I tend to do it on a Shapton gs500, then a JNS 1k, and go from there.

FWIW, it is best not to totally flatten a blade road--they are almost universally curved(Hamaguri) ootb, and not only will flattening take a long time, a single bevel with a flat blade road is a giant PITA to maintain(for me anyways).

Re: Blade road flattener?

Sun Aug 05, 2012 5:07 pm

Well it is true that single bevel knives often come incompletely flattened, but are concave because they are initially ground on large round wheels. Flattening the surface does require a lot of work. The hamaguri grind is a type of convex grind for the edge. It can be used not to flatten the blade road but to produce a more obtuse angle on the blade, much like a microbevel but blended.

When you do this depends on the knife. For a high quality usuba I would avoid a hamaguri grind entirely and go with a full flat grind. For a low quality usuba you will need a hamaguri grind or else the edge will chip out as the steel won't sustain that acute of an angle. Because you have sacrificed the acuteness of the flat grind, the cutting ability will be compromised and you will eventually go for the more acute flat grind on a better usuba to perform more highly skilled tasks. Thus beginner chefs will get a yellow usuba and suffer to better appreciate a good knife later :) They also take years to learn how to make rice.

When you get a new blade that has a significant hollow or concave grind you can flatten the blade entirely or shortcut with a convex edge, yielding the less acute angle. Just remember that it is far easier to convert a flat grind to a hamaguri grind than to reverse the process as you would have to bring the flat grind down even further because of the additional metal removed from the hamaguri grind.

You can also do a hybrid grind on a knife like a deba or kiritsuke where the tip is flat ground and the heel is a less acutely ground either using a tapered microbevel or a partial convex (hamaguri) edge. All part of customizing your knife to your own personal requirements and tastes.


Re: Blade road flattener?

Sun Aug 05, 2012 9:14 pm

Thanks! I was leaning towards the Nubatama 150, but wasn't sure if here was something better out there for this! I am looking for something to thin the blade, reshape KU style blades and sharpen the KU style blades on the full bevel and then blend the edge in. I don't need it perfectly flat (Hamaguri is perfectly fine!), but I am trying to get the concave factory grinding scratches out since they looks nasty when most of the rest of the blade road is polished! I'm not trying to do the flattening in one sharpening, but it was pretty slow going, even with the coarser diamonds! I have belt sanders I can use, but I prefer to use a stone since it makes less heat. Also, I will need a stone to set some bevels on some knives I got in, too.

Re: Blade road flattener?

Mon Aug 06, 2012 1:52 am

I guess by flattening the blade road, I meant flatten it from heel to tip, not the bevel itself from the blade grind bevel to the edge. The bevel will stay the slightly convex shape, but I wanted it more level and cleaner looking without the little dips and stuff.

Re: Blade road flattener?

Mon Aug 06, 2012 9:43 am

Another vote for the Nubatama 150. It's fast and consistant and will get you though the donkey work quickly. This stone has a number of other uses too so it's a good one to have in your lineup.

Re: Blade road flattener?

Mon Aug 06, 2012 9:54 am

Ok, Nubatama 150 it is!! Can you put one aside for me Mark?

Re: Blade road flattener?

Mon Aug 06, 2012 10:31 am

You bet buddy.
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