Flat lapping a Spyderco ceramic bench stone

[Douglas Brummett]

George Finally got my ear, so I ordered up a Spyderco ceramic bench stone to play around with. I ordered up a 302F, their 8in x 2in fine bench stone. I have heard that it is anywhere from 1800-4000g. Even the guys that work at the company who post on their forum are pretty unspecific on that topic.

It arrived yesterday and I promptly opened it up and plunked a chisel down on it. No, actually I checked it with a straight edge first. Ugh, it was well out of flat (a nice ~ shape). Might as well check it out before I raise heck with the vendor or Spyderco. It cuts nice, but like a diamond hone it has rough spots. It also feels like a roller coaster pushing a chisel lengthwise on the stone.

I have heard these things are darn hard to flatten. Several folks have posted their account of said event on blade and straight razor forums (email me for a link if you are curious, forum rule prohibit it being here in the thread). Those that have done so successfully have either used a lot of sandpaper, damaged a diamond hone, or worn down a diamond hone during the process.

I spoke to a rep at Spyderco this afternoon. His response to flattening at home was pretty much that it couldn't. If it isn't flat it needs to go back to the vendor or him. He was a good guy and really made clear that he would take care of me, but it really doesn't sound like they rework or flatten many of these stones. If it is out of spec then they replace it. I have heard mentioned the spec is .020", which is pretty bad for straight edge blades and tools used in woodworking.

Well, I got to looking at the stone this evening. I had some free time. So I laid out some 80g Norton 3X on my granite surface plate. I penciled in a grid on one side of the stone and set to work. About six strokes in the Norton 3X was toast. Wow, those guys weren't kidding about this ceramic being hard to flatten . Okay, time to pull out the big guns. Silicon Carbide loose grit, 80g lapidary. I just sprinkled that onto the 3X, using the sandpaper as my substrate. About 1/4tsp gets you about 2-3 minutes of grinding before it breaks down. After 15-20 minutes it is a good idea to swap the sandpaper, so it doesn't get out of flat (it will anyways, but not enough to be an issue).

I found it best to do this dry.
**SAFETY NOTE: wear a respirator, ceramic dust is not a good thing to deposit into your lungs. I use a 3M 7*** series.**
This prevents a big mess, allows the spray adhesive to keep the paper flat, and allows me to vacuum the swarf away.

Okay, so apply paper. Loose grit it a couple of times, vacuum, loose grit it again, vacuum.... Rinse and repeat. Inspect with straight edge and monitor progress. I also used feeler gauges to give me an indication of progress. I started with .009" hollow and a low end of about .020". It took a bit over an hour to wear down to my stopping point. I called it quits when most of the stone was flat, no light under the straight edge. The low end is only for the last 1/8" and is .002" low, I can live with that. The extra effort to get that last 1/8in would likely take another half hour and really doesn't do anything for me.

I tried to match the surface sheen of the other sides of the stone, so I finished up with 220g SiC grit on some emery sandpaper. I wouldn't recommend, but I didn't have any high grit 3X around.

I actually think that this is too polished. I may rough it up a bit with a diamond stone to hasten the cutting action. For now it cuts good, about 6-7000g waterstone equivalent but a faster cut. I am going to have to evaluate it a bit longer for more observations on how it works. I did want to put up that you can indeed flatten these without toasting a $70 diamond plate. I am out 5 sheets of 80g 3X, 1 sheet of fine emery, 2 tablespoons of 80g SiC grit, and 1/2tsp of 220g SiC grit. That's about $10.

[Danny Burns]

Ah so why did you not send it back?

[John Powers]

Thats a lot of work after the guy said send it back.

[george wilson]

Douglas,I have flattened several Spyderco's without ruining my diamond stone,but am glad to hear that you got yours flattened. I am wondering if the guys who ruined diamond stones used theirs under the faucet as I have done. Ceramic is hard,but nothing even comes remotely close to diamond on the scale of hardness. Now that you got rid of the Fuzz,I am sure that you will find the stone will give you great service. Now,the only thing you'll EVER have to do again is to hone off the little shiny steel particles that get imbedded. You could use any other stone to wipe off those steel particles. It will last forever. Just don't drop it!

My white stone is smooth also,though I flattened it with a diamond stone. Did you not get a black stone for quicker cutting,too? As you may have read,I use a 220 grit diamond hone,which you have to be careful to select a flat one,too,then a black ceramic,then white ceramic,then strop on calfskin smooth side up,glued on a piece of wood,with Simichrome lightly smeared on it. Any silver polish,or green compound from LV would work fine.

Please post again about the results when you use the new stone. My desire is to help folks here to get the fastest,best sharpening results. I have been fortunate to have tried about everything out there over the years,and arrived at this formula in the last part of my career.

IF POSSIBLE,I encourage you all to go to a Woodcraft store and hand select the flattest stone.Also,hand select the flattest diamond stone. Those solid steel ones are likely to not be perfectly flat,and you can't fix them easily. If I had to flatten a diamond stone that was a little hollow,I'd rest each end on a hardwood block,diamonds down,put a 1" wide hardwood block across the center,and squeeze it carefully in my hydraulic press. I'd squeeze it just a little-it is EASY to squeeze TOO MUCH in a hydraulic press,because it seems like you've not put any force on the work. Then,take off the pressure,and check it with a good rule. It's hard to see if those stones are flat,as the rule sits up on the diamonds,letting light in clear across the stone. The wood blocks will prevent damage to the diamonds,and bending just a little will not crack the nickle plate that holds the diamonds. DO NOT go by the backside of the stone as a gauge to see if the front is flat. The front only,is Blanchard ground,and may not be perfectly parallel.

[Douglas Brummett]

Ah so why did you not send it back?

I did consider sending it back. I did get permission from the factory to do so. However since Spyderco doesn't post a flatness tolerance and the one I have heard is worse than my stone it seems to me there is a probability that I may not get a flatter stone. I could get worse or I might get better, but odds are it wouldn't be less than .001" across the whole stone like mine now is.

Also my empirical side kicked in. I had heard mention than you can lap a fine to perform like an ultra-fine. Kind of like stone grading on a tormek. The rougher the surface the faster the cut and vice-versa. My results indicate that to be true. My stone is polishing to a higher level now. At the same time it still is cutting very fast for a stone of this level of polish.

Thats a lot of work after the guy said send it back.

Yep, see above for the logic

[Douglas Brummett]

Douglas,I have flattened several Spyderco's without ruining my diamond stone,but am glad to hear that you got yours flattened. Now that you got rid of the Fuzz,I am sure that you will fing the stone will give you great service. Now,the only thing you'll EVER have to do again is to hone off the little shiny steel particles that get imbedded. It will last forever. Just don't drop it!

My white stone is smooth also,though I flattened it with a diamond stone. Did you not get a black stone for quicker cutting,too? As you may have read,I use a 220 grit diamond hone 9which you have to be careful t select a flat one,too,then a black ceramic,then white ceramic,then strop on calfskin smooth side up,glued on a piece of wood,with Simichrome lightly smeared on it. Any silver polish,or green compound from LV would work fine.

Please post again about the results when you use the new stone. My desire is to help folks here to get the fastest,best sharpening results. I have been fortunate to have tried about everything out there over the years,and arrived at this formula in the last part of my career.

Hey George, no I didn't pick up a black or ultra-fine. I really just wanted to test the water. I have sandpaper, full set (XX-EE) diamond stones, and oil stones so I do have the full spectrum covered. No need to spend $150 to try the full set of spyderco until I had verified their usefulness in my shop. I have to say that my fears were well founded that I would get a non-flat stone. But my hopes were also met in that this is a very fast cutting stone that leaves an excellent finish. None of the random deep scratches that my diamonds tend to do.

Your results, ie not destroying a diamond stone, are not uncommon. I think the guys that wreck diamond hones are the ones who really put too much pressure on during the honing. Those who successfully lap their ceramic indicate that a light touch and letting the diamonds work would do the trick. Personally I just didn't want to risk a $40-70 diamond hone to flat lap a $45 ceramic hone. I can handle $10 worth of lapping supplies that I have already

[george wilson]

Douglas,it sounds like you are well set up. I have recommended a light touch with diamond stones several times,because,with hardness comes brittleness,plus,the diamonds might be pulled loose from their electroplated surface. I also have mentioned that I didn't find it necessary to but the extra fine stone for exactly the reasons you have cited. BTW,a good Norton India stone is a perfectly good intermediate stone. I used one for many years,and still have a few. They don't wear out any time soon,either.

ARE YOU HAPPY with the performance of the ceramic stone now?

[John Powers]

George's post got me thinking along the ceramic lines also. There's a Woodcraft down the road do I may take his advice and hand select. I remain puzzled that given the need for flatness that they don't ship them flat.

[Justin Green]

I received my Spyderco stones last week and have another, higher grit ceramic coming from woodcraft. I haven't opened them yet but will when I get home. I'm not sure I would even know how to measure how out of flat they are... any tips? I will report back with what I find.

Also waiting on the MKII from Woodcraft.

[Douglas Brummett]

George's post got me thinking along the ceramic lines also. There's a Woodcraft down the road do I may take his advice and hand select. I remain puzzled that given the need for flatness that they don't ship them flat.

It is unlikely that you could hand select a stone and inspect flatness. They are packaged in a manner that doesn't allow you to reseal it (plastic glued onto cardboard). So unless you are really in good with your local manager it isn't going to happen.
As far as flatness goes, it looks like all forming is done prior to firing the ceramic. If you have ever worked with ceramics you will find that there is always some movement during kiln firing. The out of flat condition has to do with the process. It would be better practice if Spyderco lapped the stones after firing, but I guess for knife stones they are flat enough. By doing all the forming in the soft/green state it keeps machining time and cost down. Probably the reason these stones are so reasonably priced.

ARE YOU HAPPY with the performance of the ceramic stone now?

I am going to have to get a bit more time with it to say for certain. I am impressed with how fast it cuts for the polish level it leaves. I had hoped to use it as a fine hone post black Arkansas. It appears to be finer, but I can't say for certain that it is 8000g waterstone level. After I put a few more tools to it I will have a better grasp. I did find that poor sharpening technique with a knife will leave grooves in the hone. Same can be said for all hones, this one is just harder to repair.

And yes, nothing wrong with India stones. I actually really like my India, washita, and hard oil stones. I am not overly impressed with the black though.

Justin, I used a steel straight edge. Just inspect for light showing between the edge and the stone. If you want a number for how bad a hollow or low spot is use a feeler gauge between the straight edge and the stone. Once you are down lower than .001" light is the only measure of flatness in the garage shop.

[Joel Goodman]

Has anyone compared these to the Shaptons? Or are they a whole different animal? I have neither but get a great edge with Norton waterstones but would love to avoid the constant flattening!

[Douglas Brummett]

My Shaptons will be here on Monday, I can comment then. There has been discussion over at badger and blade forum that compares the two stones. Yes, they are different animals. The Spyderco is a fired stone ceramic where the Shapton is ceramic particles in a friable resin matrix. Once flat the Spyderco will stay that way for a long time. The Shapton is like a waterstone and require flattening of about the same frequency (a bit longer, but it is far from a zero maintenance solution).

Reported cutting rates are about the same for comparable grits. The Spyderco doesn't give as much feedback. It feels like it isn't doing anything. The Shapton gives more of the traditional grating sensation.

[Joel Goodman]

I'm looking forward to the comparison -- please let us all know how they differ in a "stone off".

[george wilson]

All the white stone has to do is polish away the coarser scratches from the previous stone,just a very tiny amount of metal. A scratch only .00000250" deep on a polished surface looks prominent,so the stone isn't taking much off at all.

[Douglas Brummett]

I'm looking forward to the comparison -- please let us all know how they differ in a "stone off".

Got the Shapton stones yesterday. Honestly I like them better. They cut about the same, but they are easy to flatten and clean off. You gotta scrub the swarf out of the pores of the Spyderco. Time will tell, but for now I think the Shapton gets my favor.