# Any advice on flattening shapton #120 glass plates



## D J (Aug 2, 2020)

Hi. Awhile back I bought 2 shapton #120 glass plates with the idea that I could rub them together to flatten but when I tried, both stone's started to dish towards both ends leaving a high spot in the center. I can't remember if I was rubbing and turning 180% periodically like I do now, or maybe I just rubbed without turning. I can't afford the shapton flattening stone, so use atoma #140, it doesn't take long to wear out. Any advice or other options I could use would be most appreciated. Thank you


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## VICTOR J CREAZZI (Aug 2, 2020)

You were likely going to far with the overhang. In other words a shorter stroke should help. SiC on a large flat surface is also an option.


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## D J (Aug 2, 2020)

Thanks Victor, I don't use these stone's often, but sometimes family or a friend will bring a badly damaged knife over and they are handy to have for this


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## zizirex (Aug 2, 2020)

your sidewalk pavement


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## M1k3 (Aug 2, 2020)

You need 3 stones to flatten. I just use the large lapping plate from JKI.


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## Bobby2shots (Aug 3, 2020)

D J said:


> Hi. Awhile back I bought 2 shapton #120 glass plates with the idea that I could rub them together to flatten but when I tried, both stone's started to dish towards both ends leaving a high spot in the center. I can't remember if I was rubbing and turning 180% periodically like I do now, or maybe I just rubbed without turning. I can't afford the shapton flattening stone, so use atoma #140, it doesn't take long to wear out. Any advice or other options I could use would be most appreciated. Thank you



60 grit silicon carbide powder should be just the ticket. Easy and least expensive solution, and probably works even better than a diamond plate or the 3-stone method. Regarding the Shapton Diamond Glass Lapping plate, it's needlessly expensive, and can't be used on stones below 500 grit anyway. If you don't have a piece of float glass, try a ceramic floor tile.

Regarding technique,,,, do NOT put any pressure on the stone that you're flattening,,,,, just guide it with your finger-tips. Let the weight of the stone do the work. Circular motion,,, back and forth,,, figure 8,,,, it doesn't matter,,,, just don't overhang the stone over the edge of your float glass or floor tile.


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## D J (Aug 3, 2020)

Thanks so much


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## Kawa (Aug 3, 2020)

I have the shapton glass 120 and its by far my worst stone when it comes to glazing.
I can keep the stone flat with a 60-220 flattening stone (naniwa), but the glazing doesnt disappear (the stones remain way smoother then factoryfinish. It felt as smooth as my 600 chosera).

This forum adviced me SiC powder for lapping the sg120. Bought that and it does do wonders. The stone has that coarse, grippy feeling again.

Why am I telling this: next to whatever you will buy for flattening, get some SiC powder anyway! It is the only thing for me that keeps the stone at its original coarseness and only then you can use it for the goal you bought it for (heavily damaged knives).

You have to repeat the SiC procedure regularly on this stone, almost after every knife


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## kayman67 (Aug 3, 2020)

A cookie sheet should be available anywhere, should be cheap, should contain everything and make it easy to dispose of or keep it ready for a new session. SiC powder really makes a difference with most stones in terms of results and speed.


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## simar (Aug 3, 2020)

Another relatively cheap option is to get some 60 grit sand paper and stick it to the back of the other shapton glass and clean up the grid from the other.


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## Bobby2shots (Aug 3, 2020)

D J said:


> Thanks so much



D J, 

here's a video you may find helpful.


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## D J (Aug 10, 2020)

Finally ordered some SiC powder. It wasn't as easy to find as I thought it would be. None of the local hardware stores had it so had to search online. Found 100 grams of #60 grit for $5... postage cost $20  I have 2 big thick plates of float glass but don't want to use them for this, so found a floor tile. I'll try that first. Anyway thanks to all for the help.
David


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## Bobby2shots (Aug 10, 2020)

FWIW, you might be able to find SiC powder at a local auto-parts supply store. (used for sand-blasting)

Good luck, and keep us posted.


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## spaceconvoy (Aug 10, 2020)

Another option is to leave it alone. Unless it's really severe, a high spot in the center won't be noticeable when freehand sharpening. Instead of removing all that abrasive, I'd sharpen on it until it's dished.


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## inferno (Aug 10, 2020)

D J said:


> Finally ordered some SiC powder. It wasn't as easy to find as I thought it would be. None of the local hardware stores had it so had to search online. Found 100 grams of #60 grit for $5... postage cost $20  I have 2 big thick plates of float glass but don't want to use them for this, so found a floor tile. I'll try that first. Anyway thanks to all for the help.
> David



how did it go? 
when the crunching sounds stops its time for new powder.


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## Kawa (Aug 10, 2020)

When it isn't flat yet when the crunching sounds stops, you waited too long with flattening? 
Or do I flatten too often?

I thought it is advised to flatten after every knife you use on the stone.
I thought I was being cheap/lazy by doing it every 2 knives.

Btw. I find that a flattening stone (220 grit) is much faster then using SiC powder *for flattening.*
My pencil marks dissapear much faster with a stone. With SiC it takes maybe double the time.
But I like using (and have to use) the powder better for lapping the stone: giving them back their original coarseness.
Some of my coarse stone get really smooth/slick after use. SG120 and Naniwa pro 400 dont fit their role anymore after only 1 knife (lets say about 30 min to 1 hour)


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## D J (Aug 15, 2020)

I was going to give it a try today but I had to set it up outside, it got a bit windy. So have to delay. The SiC powder. I am sure it was $5 australian for 100 grams, the package is 500 grams. I have a photo but it shows the name, address and phone number of the seller, not sure if it is allowed to show this. It was from a lapidary supply store, I think it's used in rock tumblers. The pictures are the big floor tile I have and the two pieces of float glass I have.


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## Bobby2shots (Aug 15, 2020)

D J said:


> I was going to give it a try today but I had to set it up outside, it got a bit windy. So have to delay. The SiC powder. I am sure it was $5 australian for 100 grams, the package is 500 grams. I have a photo but it shows the name, address and phone number of the seller, not sure if it is allowed to show this. It was from a lapidary supply store, I think it's used in rock tumblers. The pictures are the big floor tile I have and the two pieces of float glass I have.View attachment 90569
> View attachment 90571


Holyyyyy Smoke,,,, how thick is that float glass? and what did that set you back? ($$$)


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## D J (Aug 15, 2020)

Haha yeah that's why I don't want to use them for this. Cost $20 aud from a local glass repair shop, it was one piece, I asked if he could cut it in half which he did. Then he cleaned the sharp edges off. I even offered more for it bit he said it was an offcut from a job he'd done and he had no use for this piece


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## D J (Aug 15, 2020)

Just measured 15mm thick 325mm width 530mm length


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## gregfisk (Aug 15, 2020)

It seems like a porcelain tile would work well for this process? They are cheap at the box stores and since they’re man made they are dead flat.


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## cotedupy (Aug 15, 2020)

I use wet and dry sandpaper for all my stones and _seems_ to work perfectly. It's so cheap and simple that I always wonder if there are advantages to other methods that I'm missing...


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## psfred (Aug 16, 2020)

Sandpaper isn't ideal for hard stones -- it tends to take the sharp edges off the stone particles, leaving the surface too smooth and slow cutting.

The silicon carbide grit will work very well, just keep a good supply rolling around under the stone and keep the swarf swept off. Try to use the glass plate evenly, as it will wear too and you will eventually get crowned stones every time. Will take a while, but it happens.

I found that using some 80 grit SiC "powder" restored my King 300 Deluxe to like new condition, I'd flattened it with 100 grit sandpaper with the result that it was flat but very very slow cutting, leaving a highly polished surface. I don't care about surface finish on a 300 grit stone, I want to hog metal off! Works great now, flattening a pile of chisels and plane blades that aren't in good shape. 

Don't use it for knives unless I have to fix a terribly chipped or blunted one, except for that yanagiba I seriously messed up trying to take a shortcut on. Be patient, it saves a lot of time....


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## kayman67 (Aug 16, 2020)

This. 

As a side note, there are many types of sandpaper. Some behave more or less like a SiC powder sheet, particles even moving around quite fast. The problem is that there's a sweet spot when going beyond will generate the same results as above.


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