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Flattening Arkansas Whetstones In The Lathe

I

IrritableBadger

Aluminum
Joined
Apr 14, 2013
Location
Harpers Ferry, West Virginia, USA
I recently inherited a bunch of Arkansas whetstones. They run the range of grades and there are a lot of different sizes.

The problem is that they haven’t been well maintained so there’s not a flat face on any of them. Some are ridiculously cupped and useless as is.

Other than needing to protect the lathe, can anybody think of a reason I can’t mount a diamond wheel like those used to cut and polish stone on the spindle and flatten the stones using a mount that rides on the cross slide?

It seems like a great idea, which makes me think I might be about to screw something up in a spectacular fashion.
 
Arkansas stones are good for sharpening knives; that's about all I use them for and really for blending in the nicks. If I want it sharp enough to whittle wood or shave with I follow that with a hard stone or a ceramic insulator an electrician gave me years ago. As far as that goes it doesn't take a flat stone to do that so whats the point?
Probable reason they're fairly flat when new is they use the fastest way to produce them, likely a saw. If it is something you feel the need to do, by all means go for it. Likely if you're a young man and use them on the high spots only by the time you pass them on to your young they might be flat again?
Dan
 
Depends on how much you value your lathe. Not sure the risk to your chuck, lathe, compound, etc. is worth the value you'll add to the stones. You're going to have abrasive dust all over.

I'd be inclined to use a diamond stone to flatten the harder ones; a coarse stone for the softer ones. A surface grinder is another option -- it's designed to handle the mess; especially with coolant. If you do use your lathe, I'd have a vacuum running as well as covering every last bit of the lathe. I was thinking of adding another step -- painting the lathe in porch paint and putting it on eBay afterward -- but you could probably get away with this with exceptional care.

Since you have to figure up a mount anyway, you might also consider putting the diamond wheel in the grinder intended for it. Just a wood frame with incremental steps would get you close enough for a final lap with a diamond stone. You might also be pleasantly surprised how close to flat(er)you might get with just a hand-held right angle grinder and the diamond wheels? That part can be done outside -- or at least away from precision tools.
 
Only if it was a lathe at your day job. Until you do it you will have no idea what a mess it will make, every nick and cranny will be filled with abrasive. I have some clue since I flatten 4" resin bond polishing pads for stone on my lathe. It is a cheap little Taiwan job from the early 80s. I mount the pads on a fixture I made in the spindle so there is nowhere for the swarf to hide, and cover everything is clean rags. What you propose is beyond what I would do to my lathe, but a surface grinder would be perfect. It would be like grinding butter with a diamond wheel, just make one set of full depth passes and your done.
 
We used to flatten the stones by rubbing them on a concrete block. This quickly gets the dish out. Then 80 grit sand paper over a flat surface.
That's it, stones do not have to be dead flat. Even a 1/4" deep dish will not effect the stones ability to hone most tools.
Your idea should work but I would encase the stone in wood first before chucking it. Very possible even slight pressure from the jaws could crack the stones. I would make a box for the largest stone with a 1/4" plywood bottom that has several holes in it so you can push the stone from the back when done. The stone can be hot glued in several places. Remove by
heating the back of the plywood with a heat gun and scrape clean . Shellac may be better than hot glue because alcohol will dissolve the glue and make clean up easy.
Smaller stones can go in the same box with a few added shims here and there.
You probably can use HSS or carbide. The stones got dished with tool steel. Same steel can flatten it. I would try HSS with a large radius.

mike
 
Thanks for all the replies!

I use the stones for sharpening my carving tools and kitchen knives. I have stones I purchased new long ago and have maintained, but most of the stones I inherited have been in my family since the late 1800’s and it would be nice to rehab and use them.

I’ll let you know how it works out.
 
The way I do it after several uses:

Start with the coarsest stone. Take the next grade of stone and rub the coarse stone on both sides using water. Then repeat process going up through the finest grade stone.

Hint: Bester is Better....
 
I flattened a hard Arkansas stone on my surface grinder using a standard Alox wheel dry and it worked OK. I have also flattened old stones by hand on diamond plated metal "stones" under water and that also worked.

Larry
 
The best way to flatten stones is to use the abrasive dust that accumulates around a surface grinder. The vacuum does not catch it all, so find a couple of tablespoons of the stuff, sprinkle it on a concrete floor and rub your stone in a figure 8 pattern on the grit. Doesn't take long. Grinding dust is not only the abrasive from the wheels but also a good part of it is miniscule metal fragments. Using a magnet, you will be surprised by how much metal is mixed in the grit and apparently that helps with removing the high spots on a stone.
 
The best way I have found to flatten stones is 60-400 grit Sic powder on a flat surface, piece of quartz countertop is what I have. Works far better than sandpaper. If you have more than .02"? of dish then you will want something a little faster.

One problem of "facing" stone is it likes to chip the edges where the tool runs off the edge and really likes to chip the corners so be gentle. I am currious what tool you plan to use. I like the zero tolerance wheels if you need a facemill for stone. FYI I use 4000 rpm and 16 ipm with plenty of water using a 3" tool.
 
water and a concrete block, or a textured concrete sidewalk. If using the sidewalk, do it in a place that does not get traffic, or that you don't care about matching - a lot of use will smooth it.

I have ground hard translucent arkansas on a my surface grinder with diamond wheel. Most shop diamond wheels are too fine, so don't crowd it if you try that.

smt
 
IrritableBadger said:
I recently inherited a bunch of Arkansas whetstones. They run the range of grades and there are a lot of different sizes.

The problem is that they haven’t been well maintained so there’s not a flat face on any of them. Some are ridiculously cupped and useless as is.

Other than needing to protect the lathe, can anybody think of a reason I can’t mount a diamond wheel like those used to cut and polish stone on the spindle and flatten the stones using a mount that rides on the cross slide?

It seems like a great idea, which makes me think I might be about to screw something up in a spectacular fashion.
Click to expand...

That's a really bad idea and a completely wrong way to flatten a sharpening stone. Better ways are:

1) buy a ceramic flattening stone designed to flatten sharpening stones. They have diagonal grooves cut into the surface. Any woodworking tool dealer will have this and always those who carry Japanese tools and supplies.
2) find a piece of float glass and use wet-dry carbide paper to flatten the stones
3) concrete block
4) flat piece of steel plate and carborundum powder
5) flatten it on a coarse ceramic sharpening stone
6) if you want to spend $200-500 buy a diamond flattening plate specifically designed to flatten sharpening stones. Shapton names these, available from Woodworkers Supply; there are other brands. Japanese woodworkers will use these plates to flatten their super expensive natural stones
 
Last edited:
LFLondon said:
That's a really bad idea and a completely wrong way to flatten a sharpening stone. Better ways are:

1) buy a ceramic flattening stone designed to flatten sharpening stones. They have diagonal grooves cut into the surface.Any woodworking tool dealer will have this and always those who carry Japanese tools and supplies.
2) find a piece of flat glass and use wet-dry carbide paper to flatten the stones
3) concrete block
4) flat piece of steel plate and carborundum powder
5) flatten it on a coarse ceramic sharpening stone
6) if you want to spend $200-500 buy a diamond flattening plate specifically designed to flatten sharpening stones. Shapton names these, available from Woodworkers Supply; there are other brands. Japanese woodworkers will use these plates to flatten their super expensive natural stones
Click to expand...

It actually worked really well. Well enough that I’m going to make a proper clamp to hold them instead of the cobbled together studs and nuts I used for the experiment.

I have lapping plates, hell, I’ve got a Lapmaster, but those things all have the same problem after the stones are really beat up. The poorly maintained stones don’t actually have much surface contact. They’re riding on a few high spots and when you apply pressure from the top you’re introducing incredible stress on the natural flaws in the stones. It’s not a matter of absolute force, so much as it is simultaneous and uneven forces coming from a bunch of different directions. That’s how I broke my favorite stone and why I went through so much trouble finding out what went wrong.

Putting it in the lathe with creative shimming and a shopvac I was able to sneak up on the high spots and introduce minimal stress to the stone. A few of the harder grade stones are over 11” and 5” wide. They give super expensive natural stones a whole new definition of expensive and, more importantly, I don’t want to break them. I’m going to use them.
 
You write:
"Putting it in the lathe with creative shimming and a shopvac I was able to sneak up on the high spots and introduce minimal stress to the stone. A few of the harder grade stones are over 11” and 5” wide. They give super expensive natural stones a whole new definition of expensive and, more importantly, I don’t want to break them. I’m going to use them."

That is another matter entirely. Those large Arkansas stones are probably really valuable; just price some that size; considerable care is needed when handling and using them.
That is why I cringed when you talked about letting them near some machine; unheard of in Japanese woodworking circles. If you have a stone worth $500 I would flatten it by hand. Maybe your jig would be safe and useful for ordinary stones. Good luck designing one that works well. Maybe a new sideline business, flattening very worn stones. If you're turning at lowest possible speed to avoid introducing stress but fast enough to get real work done a lathe might be a good solution.
 
A piece of window glass, some 60 grit wet and dry emory paper and a some water. Wet the glass and lay the emory paper on it abrasive side up. Sprinkle some more water on the paper, open a beer and lap your stone in a figure eight or back and forth or whatever. It goes pretty quick and no real need to go to progressively finer grits since the stone is the grit size. In other words a fine stone is still fine whether it has a 60 grit or 400 grit finish.
 
If you have ever flattened a stone on a surface grinder with a diamond wheel you wouldn't ever think of doing it any other way, if it has much dish.
 
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