Thread: Unknown Japnese hone hurting my head...

This hone is rather hard, soaks a little water but nothing like a norton, and feels great with my razors... Now untill today I was convinced that it was in the 6k range. Today I decided to refresh one of my Robeson blades that was pulling just a bit. Thinking a few passes on this hone and a few on the coticule and I should be ready to roll... Ya well after a few passes I started wondering when this stone began to act like a glass plate vs a 6k(ish) stone. I could hear the same amount of grind but it felt smooth as glass and the polish was fantastic... Now WTF??? I had to get my lenses to see if the stone was hitting the edge at a weird angle or something but I didn't see anything to explane why this hone (not lapped in weeks) is now feeling more like a 16k+ stone...

Can anyone shed light on whether these abrasives break down with use and become finer with use. Or of the way I'm lapping it (325DMT) is causing it to be rougher than it wants to be, thus getting finer feel with wear. The hone is still dead flat.

Help...

Changed the title to match the hone in question

I'm sure there's a lot of folks who could give you better information than me, but one thing I will say, is that there's a lot more to the way a hone works than just the grit. The size, shape and hardness of the grains of the hone can make a HUGE difference.

That's why given 2 hones of the same grit, one may be a very fast cutter, while another may be more of a polisher.

In my book, (and this comment applies to everything in life, not just hones) all that matters at the end of the day is how something works for you.

Whoo hoo thanks for the pointer on the make, I can look for info now Or at least write it down and not forget it as fast

As for rinsing, I do tend to get it a bit wet at times and I'm sure that would count as rinsing it off.

I have considered getting the DMT 4k or 8k plate just to touch up the high grit stones after lapping. I know the 125 plate leaves a wicked rough finish that is not acceptable past 4k, I use the 325 at the moment past 4k. It does a great job at the 8k lvl though. I have heard that after 8k you get a better working stone if you use an even finer (that what I have) plate after flattening. Hop that made sence...

If I do indeed have a finishing stone here (WHOOT $50 finisher) I'm going to have to find something in the 5k range to take it's place...

I guess only time and a lucky search hit will tell

Originally Posted by OLD_SCHOOL

The abrasives of Japanese hones are said to break down and become finer with use, so it is possible this has happened.

That makes me wonder, how does lapping affect this? would repeated lapping with fine grits cause this sort of Japanese hone to become finer, or would it more or less "undo" the process?

I'm thinking that would depend on how it was lapped. Given I know what the DMT 325 does and feels like, I would say my current method would not help it get finer by it's self. However if I used a finer abrasive or it's own slurry on a glass plate, I could see a posable refinment of the surface.

In theory

Observations can be dependent upon expectations. If you are expecting 6, it's possible to believe 6 until the weight of experience proves otherwise.

the size of the lap scratches will not change the size of the abrasives. So far as I know.
Fwiw-I don't notice scratches on my hones surfaces from 400 diamond plate.

I use 1200 as diamond nagura, or another finish hone, or same stone as nagura depending on mood or intent. again fwiw

perhaps one difference_a stretch here- the coarse scratches create more surface area for water to act on, thus more binder to break down releasing more abrasive

after initial lapping i guess you rinsed it; or did you use the slurry present?

what I hope you will find is that with use of a nagura you get a 6000 grit action- then as you wash up and continue you get quick cutting 12-16+ finish

From So's web page:

Mt.Oohira is situated on the west side of Kyoto. Oohira is the name of the mountain and at the same time the name of the quarry. Another famous stone, Mizukihara, is from the Mizukihara quarry which is also in Mt.Oohira. Oohira quarry and Mizukihara quarry is opened at the different altitude, and the owner of the mining rights are different, thus they are regarded as different quarries, thus different stones. Oohira's history goes back to pre 19th century, when they produced stones for polishing the swords.

Not particularly illuminating I guess, but a start nonetheless.

I too have heard of the particle breaking down argument with natural Japanese stones, and I think I may have experienced it on a couple of mine, but I have never really tested it extensively.

I have also heard with older stones that have been laying around for a while that they can develop a "skin" that, after removal by lapping, can reveal the true nature of the rock. However, I also heard that this skin is usually not very thick. I do not know how many times you have lapped it Chef, but that pic shows the stamps, so perhaps what has happened is that this top layer has been lapped away?

Whatever the reason, sounds like you have a nice stone there! Congratulations!!

James.

I took the picture before I lapped it, the kenji are long gone now. I do rinse off the slurry after lapping. I think I have lapped it 2 times in the past year, very lightly as it didn't seem to change much.

I'll be using a different razor tonight to see how it reacts. I have a german razor with bone scales that I finished and want to see how it feels... The blade is in rough looking shape but the scales are nice.

Originally Posted by OLD_SCHOOL

I made a small typo in that quoted text, it should have read during use, not with use.

I'm not sure what repeated lapping would do other than waste away a natural product.

Ah, that makes more sense. Although it still suggests an interesting experiment for somebody with hones to spare. Perhaps you could dry sand the surface before use to create a finer surface, or find some other way to accelerate the process.

I have absolutely no idea if such a thing would work, or be all that useful if it did, but it's an interesting thought.

stop hitting your head with it then!