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Nubatama 150 supposed to work like this?

Sun Aug 11, 2013 5:15 pm

I've recently bought my first waterstones; The Nubatama set minus the accessories. So far I'm getting pretty good results from all 3 stones. I guess I should list them: Bamboo 150, Ume 1000, Bamboo 5000.

For new stones and a new system, I guess I'm pretty impressed in that I've gotten quite good edges from them, if not my best. But the 150 has me confused.

It stays very dry when using it. Initially I though I hadn't soaked it for long enough, so I did an experiment and soaked it overnight last night. I used it today for about 2 hours on a big reprofiling job. Straight out of the soak it dried out in perhaps 20 seconds. When adding more water to it, it pools up on top, then totally soaks in, taking maybe 20 to 30 seconds... 45 max. At which point it's dry and the feel and sound change.

When it's wet, it's quiet. As I'm stroking and it dries out, it gets much louder and then particles start to break off of the stone. It forms a gritty paste that's both black and brown. Seems to be a mixture of the stone particles and metal that's been ground off of the blade. In fact the black seems to load up in the stone fairly quickly. When I flush it with water and rub it with my fingers I can get all of the brown grit off. I can get a lot of the black off. But some black remains on the stone. I'm not too concerned about this, as it continues to cut pretty quickly. I ground off a lot of metal today.

But I'm wondering if it's supposed to dry out so quickly. I wonder if I'm damaging the stone by continuing to grind on it when it gets dry and gets SO much louder. The change in sound is so severe, it's almost like I raised the knife up 10 degrees and have started cutting into the stone. It caught me off guard the first few times it happened. I find myself re-wetting the stone every minute or two, which uses a lot of water, makes a big puddle, but still doesn't keep the stone wet 100% of the time.

Ok, this is way too much on this one topic, but I wanted to give a complete picture of my experience and see if it matches others that have used this stone.



Re: Nubatama 150 supposed to work like this?

Sun Aug 11, 2013 5:46 pm

Hi Brian,

The 150 and other coarse stones - especially below 400 or so grit are quite porous so you can expect it to drain quickly. Some of the really coarse stones like the 60 grit and Aratae or ~ 24 grit stone drain so quickly that you can pour water in and it runs out just as fast.

Soak the stone and then just start using it supplementing it with water splashes as necessary. As it builds a bit of mud the mud will act as a bit of a barrier to keep the surface wet a bit longer. It is a thirsty stone, but it cuts so quickly that you are usually done doing what you need to - reprofiling or tip repairs for instance before you need to spend more time on keeping it wet. Check out the video I did with the stone from the CKTG site.

The 150 also works very well with the Atoma 140 plate or other diamond XXC plates to convert the diamond scratch pattern to a stone scratch pattern, so it can be used very effectively with the diamond plate as a team for reprofiling jobs.


Re: Nubatama 150 supposed to work like this?

Sun Aug 11, 2013 5:57 pm

+1 to what Ken said. Once I build a good mud on my 150 it stays hydrated and doesn't lose water as fast.

Re: Nubatama 150 supposed to work like this?

Sun Aug 11, 2013 6:21 pm

Only add water when the mud seems dry. You want the mud to build and by constantly flushing the surface you are only making the stone work slower.

Re: Nubatama 150 supposed to work like this?

Mon Aug 12, 2013 5:27 am

Ok this is new info!

That gritty paste I'm forming... which would be called "mud" on finer stones... I want to keep that on the stone? It seems... wrong. But I'll try it. I've still got work to do on the big knife I was reprofiling yesterday. Don't you just love knives that have just about never been sharpened and have been beat on like crazy? :)

Thanks for the help guys.


Re: Nubatama 150 supposed to work like this?

Mon Aug 12, 2013 6:01 am

Yes, keep the mud on the stone and let it work for you. The stone will cut much faster with the mud.

Re: Nubatama 150 supposed to work like this?

Mon Aug 12, 2013 5:26 pm

Ok, just spent another hour plus trying to reprofile this blade with the Nubatama 150. It's slow going but that's mainly because I'm checking often and being careful. I tried to leave mud on the stone as much as possible this time and it worked fine. I'm not sure it cuts any faster, but it *is* cutting the D2 steel.

I didn't use any where near as much water as before. The biggest factor now is all the mud that sticks to the blade. No big deal, just extra time.

But all this mud formation makes me think that I'm definitely going to have to flatten this stone. Probably sooner than later if I do jobs like this with it. What's the right thing to use? I've read over and over that the DMT XXC is a great stone flattener. But it's very close in grit rating to this stone. Is it going to be more likely to strip the diamonds off of the plate?

I've read about people using drywall sanding grid for this, but I'm not sure how you'd make that "flat" to start with. Seems like flattening such a coarse stone might be problematic.

So far, I'm not sure this stone is any faster, or even quite as fast as, the DMT XXC. But it's s cool stone either way.


Re: Nubatama 150 supposed to work like this?

Mon Aug 12, 2013 9:00 pm

I soak my 150 full time and I find it most useful for bevel thinning and generating a consistent burr which it does lightening quick. However I don't prefer it for heavy profiling and removing alot of steel. For this task I've been employing the Ume XXC. It doesn't compare to a belt grinder but it's cheaper and still eats steel like nobody's business. Plus when rubbed against the 150 they both stay flat.


Re: Nubatama 150 supposed to work like this?

Mon Aug 12, 2013 9:52 pm

I wouldn't use the DMT XXC on a coarse Nubatama. I use a 60 grit Ume stone or a large flattening plate with coarse silicon carbide powder.

Re: Nubatama 150 supposed to work like this?

Tue Aug 13, 2013 9:19 pm

I flatten my Bamboo 150 with a DMT XXC. I've not seen any issues stripping diamonds but will keep an eye out.
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