Spyderco Stone Flattening

[Aerosmith101]

I just got a Spyderco UF bench stone but it's not flat, from what I've read this is fairly common, I've been having trouble flattening it on a diamond plate, does anyone know a faster way to flatten it?

 

[bgentry]

You're talking about the 302 or 306UF right? The big bench stones? I have the 302 and never measured it's flatness, but it seemed plenty flat for knife sharpening. How out of flat is it? Is this an academic exercise, or is it dished or misshapen enough to be a problem?

I ask because the sintered ceramic this stone is made of is rather hard and definitely requires diamonds to cut it. But the real issue is that the surface finish of this stone is specific. Meaning that Spyderco uses a certain diamond cutting tool to cut this stone flat and the finish that it imparts is part of the UF rating of this stone. Using another type of diamond abrasive on this stone will alter this surface finish and might make it polish differently than it does from the factory. Highly likely actually. In fact, the Fine and Ultra Fine Spyderco stones are EXACTLY THE SAME, except for the surface finish imparted by the diamond cutting tool used to finish the surface.

If it's really not flat in a severe enough way to interfere with sharpening you should contact Spyderco. I almost guarantee they will make it right.

But if this is just it being out by a few thousandths across its length in one direction or another... I think you should just use it. Minor differences in level from one end to another shouldn't affect normal hand sharpening. In my opinion.

Brian.

 

[FortyTwoBlades]

The UF should be flat. The F probably isn't. They're the exact same stone, but the F is left as-fired and the UF is machined smooth. That process should have made it quite flat.

 

[annr]

Someone else recently had this issue, and they successfully exchanged the stone. (Personally, I like dead flat/true, so I would look into an exchange, but everyone has different needs.)

ETA: I have F and UF and I used them on straight edges.

 

[David Martin]

There have been several members that have leveled the ceramic stone you have and written about it. Here is one, done by cerealkiller a good job. I did mine in a similiar fashion. DM https://www.bladeforums.com/threads...one-into-a-combo-stone-write-up-pics.1163228/

 

[David Martin]

Aero, I purchased the fine ceramic stone and after checking it I found one side was very flat and the other was not. So, I decided to
flatten it using a coarse DMT stone that was already worn. I determined the area that needed it most, marked it and started rubbing it, using plenty of water. It took me about 45 mins. of rubbing with this plate and then it looked good. I finished it off with the fine diamond, checked
it again and it still looked very level. Then checking my coarse diamond(duo) I noticed it was shot and tossed it. The fine diamond plate (dia)
still had some life left in it. So, I kept it. That side of the stone is now much finer that the fine. So, I now have a fine and x fine from my efforts by accident. Thus, I saved myself 80$ by not having to purchase the additional ultra fine stone. It was a challenging project.
However, if you don't care to under take this, then send it back with a letter stating why and they tend to send out a more level ultra fine stone. Good luck, DM

 

[Bill3152]

SIC powder (silicon carbide)works great on a granite tile then use some wet/dry to finish it the way you want.

 

[FortyTwoBlades]

SIC powder (silicon carbide)works great on a granite tile then use some wet/dry to finish it the way you want.

That method will prove difficult with a sintered ceramic stone. The way it usually works is by creating pressure concentration on the grains, which breaks the bond of the stone. That won't work very well here, as sintered ceramics are fused under incredible heat and pressure until the abrasive grains themselves have fused together. So you're basically limited to abrading the surface flat instead, and rubbing on free abrasive isn't a great way of accomplishing that. I'd use a cheap Chinese lapidary disk from eBay if I were going to bother with flattening one. Any diamond stone you use kind of has to be treated as disposable because it'll be used right up in the process.

 

[Obsessed with Edges]

That method will prove difficult with a sintered ceramic stone. The way it usually works is by creating pressure concentration on the grains, which breaks the bond of the stone. That won't work very well here, as sintered ceramics are fused under incredible heat and pressure until the abrasive grains themselves have fused together. So you're basically limited to abrading the surface flat instead, and rubbing on free abrasive isn't a great way of accomplishing that. I'd use a cheap Chinese lapidary disk from eBay if I were going to bother with flattening one. Any diamond stone you use kind of has to be treated as disposable because it'll be used right up in the process.

This.^ Especially with the larger ceramic stones.

I've tried glass-backed wet/dry sandpaper for refinishing these Spyderco hones (smaller ones). It's almost like rubbing two pieces of smooth glass against one another, with very little abrasion going on with either surface and almost no swarf generated in doing so. If it changes anything at all on the stone, it'll just be a very light polishing/burnishing of the finish; that's usually not a good thing with a Med/Fine/UF ceramic hone, and will diminish the hone's cutting effectiveness.

I've used a diamond hone (either/both of a DMT Coarse & Fine) to flatten three of my smaller ceramic hones (Lansky, Spyderco). It works; but even then, it takes quite a long while and also leaves the finish on the ceramic finer than it originally was. That speaks to the importance of choosing the right diamond grit for the job; I would've done better using an XC or maybe even XXC instead. You can help protect the life of the diamond hone by keeping pressure light and using plenty of water to flush the swarf away (I did mine fully immersed in a pan of water).

Depending on how the Spyderco stone is out-of-flat, it may or may not matter so much anyway. If there's some 'crowning' of the stone's surface toward the center, I wouldn't worry about it. On the other hand, the smaller Spyderco hone I flattened had an issue with cupped surfaces, meaning the edges of the hone were raised above the plane of the stone's larger surface. This caused some major problems in sharpening, if/when the blade's edge was dragged across the raised edge of the stone; it instantly rolls the knife's edge and destroys any good sharpening work done in an instant, single pass. If seeing this again on a new stone, I'd just return it to Spyderco for a replacement.

 

[eKretz]

It will work with loose grit SiC but you'll need to keep the grit freshened much more often than with lapping other materials. I've done a 3" x 8" UF with SiC and it worked just fine. Just take care not to try to work the grit too long because it gets fractured and turned into fines pretty quickly.

 

[David Martin]

Folks like the dia diamond 'Hard Coat' plate for lapping water stones. Seems like it could be used here. DM

 

[eKretz]

It could be, but the result won't be much different than a regular diamond plate. I tried a brand new "hardcoat" lapping plate on a UF and it got worn and slowed just the same as my regular diamond plates did when I tried lapping Arks. The "hardcoat" might help keep the diamond particles in place a bit better but it can't make them any harder.

 

[David Martin]

I think that's what the mfg. was after,-- the anchoring of the particle. Plus, water stones are way softer than these stones we are leveling. DM