Maintenance requirements for ceramic stones?

[Patrick C Daugherty]

Please, this is not a question asking how to best sharpen hand tools, it is a simple question to ceramic stone users. How hard are they to maintain? My diamond plates are years old and do not cut as aggressively as in the past. I have a selection of water stones of known and unknown grit for which I have been unwilling to get my mind around the kabuki dance necessary to use them effectively. I do use the 6000 grit stone for polishing, but only because I can use it without soaking. Before I spring for a new set of diamond plates, I thought I would ask the question. I find the maintenance info on the vendor sites somewhat confusing. Thanks

[John C Cox]

It would help to know specifically which ones you are asking about, as they are all over the map based on manufacturer and hardness. Some are fairly soft and wear in "faster" where others are harder and wear in more slowly. Of course, the softer ones tend to cut faster and are also easier to flatten

Also, different manufacturers use different formulations, and have different recommendations for cleaning and lubrication.

[Mike Brady]

Chris Schwarz has a blog entry on this topic that he posted just yesterday. He really substantiates his conclusions and cuts through (pun intended) the fog surrounding stone types, flattening, care, and so on. Actually, the stones he recommends I have not even heard of, and I have reading forums since the early 2000's.

[Frederick Skelly]

I own several Shaptons. The ones I have are easy to maintain. I flatten using this $59 item from Sharpening Supplies. LINK.

FWIW, I also saw a Stumpy Nubs “review” (infomercial?) on an 8” CBN plate for flattening that cost about $100.

[Patrick C Daugherty]

John, your post basically describes my delima. I am looking for fast aggressive cutting and low maintenance close to diamond plates.
Mike, Thanks for the heads up on the Schwartz blog post. I will go there.

[John McCrea]

I guess it all depends on what you consider "low maintenance" to be...

I have a set-up of 4 Shaptons: 500, 1000, 4000, 16000 (a polisher that takes the place of a strop).

What I like about them is the fact that you don't have to pre-soak them. Just pull them out, sprinkle a few drops of water on them, and go to town.

They're pretty easy to lap — no real difference compared to ordinary Naniwa, Norton, Chosura whetstone. And, in my experience, they wear just a hair slower than ordinary whetstones. I lap mine in a utility sink to occassionally splash them with a little water. But you can lap them with a few spritzes from a spray bottle as well (likeRob Cosman does).

(I use Shapton's diamond lapping stone ... just because I knew for certain it would course enough to lap the 500 ceramic plate, I wouldn't have to worry about it going of flat since it's diamonds embedded right in float glass, and it doesn't need to be pre-soaked either. A DMT would also suffice as long as it's course enough to handle your coursest ceramic stone.)

So, to me, they are "lower maintenance" due to the fact, while they they need about the same amount of lapping, I don't have to worry about constantly keeping them wet. Just pull them out, put a few drops of water on them, and get to work.

In all honesty though, you can probably get the same results with even less maintenance with a set of DMTs followed by a pasted strop ... like Paul Sellers or James Wright (Wood by Wright)...

In that set up, you don't even have to worry about lapping. Or pre-soaking.

And it'd cost a little less since there's no need to buy a lapping stone.

It's probably what I would've done if I didn't already have two of the four Shaptons on hand for sharpening straight razors and kitchen knives.

[Jimmy Harris]

The only maintenance required is flattening the stones. I own the same one as Fredrick, sold under the "Sharp Pebble" name for about half the price.

Now, they'll cut better and last longer if you wet them appropriately. Some, usually higher grits, are just splash and go. Most of the lower grits work best if you soak them first. They all require you occasionally splash them with fresh water, so they are best used around a sink. And you want to wash off the swarf when you're done. Just rub them under running water with your hand is all that's required. And they don't require flattening every time you use them, but the more often you flatten them, the easier it is to flatten them. Just take a pencil and make some witness marks across the top and rub the flattening stone across it until the marks are gone. Then place them somewhere so they can dry evenly.

A couple of things about the flattening stones to keep in mind, if you get the regular flattening stones, you treat them more or less like a whetstone. In other words, soak them in water too, and let them dry out. Also, flatten your whetstone by going front to back, and side to side, and then turn it 90° and repeat. That way you wear the flattening stone evenly along with your whetstone. And it's a good idea to round off the corners of your whetstone, which just takes a few swipes.

The good thing about whetstones is they don't get dull. As you use them, you expose new material. So they always cut like new.

The one thing diamond plates have over ceramic whetstones is not needing water. You can usually just spray some lubricant on them and go to town. Then wipe them off when done. But flattening a ceramic stone doesn't take long if you do it often. Maybe 10-20 seconds. And if you're already soaking your whetstone, might as soak your flattening stone at the same time.

I moved away from ceramic whetstones because I don't have water in my garage. And that made it too much of a hassle for me. I switched to sandpaper glued to plate glass and a water spray bottle. To me, it's kind of the best of both worlds. A lot of people say you'll waste money on sandpaper, but I think they must change out sandpaper too often, because a single sheet of sandpaper will last me probably 50 sharpenings. Sure, it dulls noticeably after 3-5 sharpenings. But it'll still cut at 80% efficiency of brand new for the next 50 or so sharpenings.

[Mike Henderson]

I tried a lot of different ways to sharpen and settled on Shapton stones and DMT diamond plate to keep them flat.

Mike

[When you rub two stones together, you don't get two flat stones. You get two stones that conform, usually one convex and one concave. That's true for the "flattening stones" that Norton sells.]

[Jimmy Harris]

...
[When you rub two stones together, you don't get two flat stones. You get two stones that conform, usually one convex and one concave. That's true for the "flattening stones" that Norton sells.]

This is true if you just rub them together the same way every time. I distorted my flattening stone doing this not long after I bought it. I since learned you have to continually rotate the flattening stone and the whetstone so you're not contacting the same part of the flattening stone to the same part of the whetstone. That'll keep both relatively flat a lot longer. So I make a couple of passes, rotate my flattening stone 45°, make a couple more, rotate it another 45°, then rinse and repeat. I also alternate my strokes so sometimes I'm moving the flatting stone along it's length, sometimes along it's width, and sometimes in circles. By constantly changing both the angle and direction, you average out any imperfections in both stones.

And here's another tip. If your flattening stone does get out of flat, just take it to a concrete sidewalk or driveway, and rub it against that to flatten it. I used to do that to my whetstones to flatten them and refresh their surface before I bought a dedicated flattening stone, as it's a trick that also works on whetstones. Concrete is a powerful abrasive, and they're usually poured pretty flat. Just again, move it around so you're not focusing on one area to average out any inconsistencies.

[Mike Henderson]

This is true if you just rub them together the same way every time.

I'm afraid that's not correct. Two stones rubbed together, in any direction, in any order, etc. will not provide two flat surfaces. No matter how you try, one will generally wind up convex and the other concave.

There's a three stone technique that some people claim will give a flat stone, but the only way I've been able to get them flat is to have a reference flat surface. That can be sandpaper on a flat surface such as your table saw, or a diamond plate. And note that this is just "woodworker flat". A machinist would laugh at it.

Mike

[Jimmy Harris]

I'm afraid that's not correct. Two stones rubbed together, in any direction, in any order, etc. will not provide two flat surfaces. No matter how you try, one will generally wind up convex and the other concave.

There's a three stone technique that some people claim will give a flat stone, but the only way I've been able to get them flat is to have a reference flat surface. That can be sandpaper on a flat surface such as your table saw, or a diamond plate. And note that this is just "woodworker flat". A machinist would laugh at it.

Mike

And yet it works anyway.

Now, I agree that it won't stay within 0.00001 mm of flat or something crazy. But I've been doing it this way for many, many years, and my experience proves, that at least the way I do it, it does indeed work. At least within the tolerances needed for woodworking.

Think of it like this. If you have one stone concave and one stone convex, and flip one 90°, then when you rub them together, the protrusions will now be in opposition, instead of complimentary. Now you may think that'll you just wind up making them convex and concave across multiple dimensions, instead of the one doing it this way. And you'd be right. But if you gradually move the stones across while working them back and forth so you're not rubbing the same two spots against each other, you can largely avoid this. It works by averaging out any inconsistencies, and it works best before you've developed a deep dish in either stone. If you get too far away from flat, you're best bet is to start over against a reference surface, because at some point the stones will want to wobble against each other, and you can't easily find and maintain your average point to reference against. I usually just use my driveway for this, as it's flat enough for woodworking tools.

It works on the same principle as hand planing a severely warped board. You attack it from multiple angles to average out any inconsistencies created from using a plane that's much smaller than the board itself, and will thus never truly present a flat, reference surface. And just like hand planing, it'll never produce a truly flat surface within 0.00001 mm or whatever, but it will provide, if done right, a surface flat enough for woodworking.

[Mike Henderson]

Years ago, amateur telescope makers used to grind their own mirrors. The way you do it is to have a mirror blank and a tool. You put abrasives between the two and rub them back and forth, occasionally changing the direction of motion. The goal, and the eventually outcome, is that the top blank becomes concave. It became concave because no matter the direction of motion the center was abraded so the center became deeper compared to the sides.

This is pretty primitive but works because as long as the worker keeps changing the direction of motion, the result is a spherical concave shape in the upper blank.

No matter how you try, you generally cannot escape one surface becoming concave and the other convex. The will conform, but they will not be flat.

[If you're going to let one go concave, you'd be better off if it was a single "dip" in the stone, rather than a hole. With a dip, you can still get a straight hone on your chisels. If it's a hole, the chisel will not hone straight across. A lot of our ancestors used to let their oil stones develop into a dip and they were able to sharpen very adequately. The dip occurred because when you use a stone, you always use the center more than the ends, no matter how you try. Based on most of the old chisels I've bought, our ancestors never used to flatten the back of the chisels, so they didn't need a flat stone.]

[Cameron Wood]

Years ago, amateur telescope makers used to grind their own mirrors. The way you do it is to have a mirror blank and a tool. You put abrasives between the two and rub them back and forth, occasionally changing the direction of motion. The goal, and the eventually outcome, is that the top blank becomes concave.

This is pretty primitive but works because as long as the worker keeps changing the direction of motion, the result is a spherical concave shape in the upper blank.

No matter how you try, you generally cannot escape one surface becoming concave and the other convex. The will conform, but they will not be flat.

[If you're going to let one go concave, you'd be better off if it was a single "dip" in the stone, rather than a hole. With a dip, you can still get a straight hone on your chisels. If it's a hole, the chisel will not hone straight across. A lot of our ancestors used to let their oil stones develop into a dip and they were able to sharpen very adequately. The dip occurred because when you use a stone, you always use the center more than the ends, no matter how you try. Based on most of the old chisels I've bought, our ancestors never used to flatten the back of the chisels, so they didn't need a flat stone.]

I have duplicate water stones- 800, 1200, & 8000. I flatten them by either rubbing two like ones together, or rubbing a stone with a diamond plate (260 or 400). I have been doing this for a long time. I can detect no difference in flatness between the two methods when checked with a precision aluminum straight edge.

So unless you are talking about a time scale where the diamond plate is wearing out of flat, I say B.S.. I am familiar with the lens grinding technique. Comparing to wood, you can make a convex, or to some degree concave surface with a hand plane, but that does not mean that no matter how you try, a flat surface cannot be made with one.

[Mike Henderson]

Let's examine how two stones work together. Let's assume one is worn in the middle and the other is flat (for an extreme example). As you rub those two stones together, the center of the flat stone will not be abraded as much as the ends and that stone will become convex. That's true, no matter what process you use to rub the stones together.

Eventually, the two stones will come into full contact and the flat stone will be convex and the other will still be concave.

If you have a technique to get two flat surfaces by rubbing two stones together - run out and patent it.

Mike

[When you rub two stones that are concave together, they will almost never be the same amount of concave so the same effect occurs, just a bit less than if you start with one stone flat.]

[Warren Mickley]

Let's examine how two stones work together. Let's assume one is worn in the middle and the other is flat (for an extreme example). As you rub those two stones together, the center of the flat stone will not be abraded as much as the ends and that stone will become convex. That's true, no matter what process you use to rub the stones together.

Eventually, the two stones will come into full contact and the flat stone will be convex and the other will still be concave.

If you have a technique to get two flat surfaces by rubbing two stones together - run out and patent it.

Mike

[When you rub two stones that are concave together, they will almost never be the same amount of concave so the same effect occurs, just a bit less than if you start with one stone flat.]

I was trained to sharpen in 1960, and taught to use two stones for flattening in 1967. Somehow we have managed to be woodworkers for centuries without diamond flattening plates and granite surface plates. We did not need someone sitting at a screen telling us what will work.

I understand your theory, but in practice we do not work mindlessly- that is machine thinking (coming up with a procedure that someone follow with their eyes and brain closed.