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Cleaning and/or flattening stones

Tue Sep 11, 2012 11:36 am

I'm asking this question about all stones, all grits, etc. but the question came to me in regards to finer grit stones, specifically the Shapton glass stones (for EP) I just got. I want to keep them in good shape and not wasting any stone more than necessary. I think flattening stones is a waste of stone, however it is a necessary waste most of the time. If you sharpen a lot of long blades with flat edges the stones need to stay flatter it seems than if you sharpen mostly smaller folding or fixed blade knives. Edges that are curved will still be touching a dished stone when a long (over 6") blade may only be touching the stone on the outside edges. So, my question is how to keep the stone performing without flattening it. I have just used water and dishsoap to wash the Shapton stones and they get pretty white. Not like brand new but pretty close. So what are your thoughts on washing compared to flattening stones when it comes to performance? Also, any suggestions on what to wash the stones with. Any help is appreciated.

Jack

Re: Cleaning and/or flattening stones

Tue Sep 11, 2012 3:04 pm

Don't know if I would use soap, it can have oils in it that can damage some stones.

Keeping a stone flat has many schools of thought and none of them are really wrong. Flatness of the stone is good when working on large blades and wood working tools although may be more in the mind of the user than the physical qualities of the tools.

Nothing is flat or straight or perfectly ground. Everything has grooves or defects, bumps and scratches. So how flat is flat when the blade is flexing and the stone is breaking apart under pressure? Pressure is another funny subject because it can cause so much to go right or completely wrong. At any one time do you know how wide a area you are contacting on the stone? At best maybe a inch but most often only a few millimeters. The size of the contact area is what its all about, everything will bend, flex, deform, and contort. It's up to you to compensate for each occasion.

Re: Cleaning and/or flattening stones

Tue Sep 11, 2012 9:00 pm

I use at Nagura stone to keep my water stones clean. It will keep the Shapton Glass stones in pristine condition in regards to the actual cleanliness of the stone, works fast and is quite cheap to purchase.

I flatten my stones with the DMT XC plate but I don't find the glass stones wear all that quickly, especially the full sized ones.


Nagura stone, works great.

Peter

Re: Cleaning and/or flattening stones

Fri Sep 21, 2012 3:07 am

Flattening a stone removes high spots. Sharpening on a non flat stone preferentially removes even more on the low spots - thus it causes more rapid dishing, so flat stones last longer. If you wish to minimize dishing do it by preferentially sharpening on the high spots so you need to flatten less and less often. Understand the style of your sharpening as it pertains to the wear pattern you make - usually an X with the lowest part in the middle for freehand sharpeners. So use short strokes on the corners to balance it out and do strokes the full length of the stone - but don't go over the edge of the stone :)

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Ken

Re: Cleaning and/or flattening stones

Fri Sep 21, 2012 7:34 pm

The main reason I use a diamond plate on my stones is to clean them, not flatten them. They stay pretty flat through sharpening, but it does help to push down the corners--dealing with flattening the very corners through sharpening can be tedious.

I have never washed a stone, like with soap and water. No reason other than that I've never needed to, and the box on my first stone was like "DON'T EVER PUT SOAP ON THE STONE OR IT'LL EXPLODE!" so I just didn't do it.

Re: Cleaning and/or flattening stones

Sat Sep 22, 2012 9:09 pm

I also don't wash stones with anything other than the water used in sharpening. On a rare occasion I used some Dawn dishwashing liquid to help remove a drop of oil that landed on a 12k Naniwa Suoerstone with moderate success. Oil on synthetic stones is a very bad thing and results in a spreading dead spot on your stone. It didn't affect the stone but the exposure was short and limited.

I'm of the 'precise' mindset and feel that a flat stone surface is a distinct advantage in getting a more precisely defined edge geometry. Most people tend to agree with this. I find diamond plates an ideal way to do this, with the cleaning effect an added bonus. You can flatten with other stones equal or coarser than the stone you are using. Some, like Murray Carter tend to 'hit the high spots' to keep the stone relatively flat. Some like Harrelson Stanley are even more fanatic about stone flatness than I am.

Recently I have built a flattening jig that not only flattens a stone but squares the stone so that the two sides of the stone are perfectly parallel to each other. I find this particularly useful for stones used on the EP and other precision devices (WEPS, etc). Customers who I have 're-tuned' their stones report marked improvements in sharpness. At this time, I'm leaving the details of this jig proprietary (sorry).


I'll also share an interesting observation. If I use a drop of CBN on a stone (of similar grit) I find that this essentially prevents swarf buildup on a stone. What happens is that the stone abrades a bit quicker so the metal swarf doesn't 'stick'. And of course the stone cuts faster too, especially on abrasion resistant steels.

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Ken
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