New Spyderco bench stones, far from flat ?

[Lasse Hilbrandt]

I decided to try and flatten them my self. The Medium went ok with about 30 minutes work on my DMT flattening plate.
The fine one is more of a work. This is the result after 30 minutes. I think my flattening plate is close to toast.

Spyderco.jpg

This is going to be 2 very expensive sharpening stones

[Reinis Kanders]

I also ruined one dmt xxfine diasharp stone on spyderco ultrafine. Afterwards I swithched to much cheaper plastic single sided honeycomb DMTs and they have lasted. They in general work well for initial flattening things because slurry does not lift them up as fast as it happens with more expensive diasharps.
Afterwards I used my DMT on 10x3 hard Arkansas stone to remove about 1/16" twist, and it still works.

I decided to try and flatten them my self. The Medium went ok with about 30 minutes work on my DMT flattening plate.
The fine one is more of a work. This is the result after 30 minutes. I think my flattening plate is close to toast.

Spyderco.jpg

This is going to be 2 very expensive sharpening stones

[Lasse Hilbrandt]

The problem with anything but the DMT Dia-Flat is that the Spyderco are so long 8" that it is as long or longer than all other lapping or sharpening plates. Except the Dia-Flat which is 10"
That makes it difficult to flatten the Spyderco.

[Patrick Chase]

Has anybody tried lapping these things on SiC grit?

Once a long time ago I stripped a Dia-Flat nearly smooth by using it for initial flattening of a Sigma S-II 240. Ever since then I've lapped very coarse water- and oil-stones with loose SiC grit (ranging from #24 to #120 depending on the stone I'm flattening) on a granite surface plate, with a sacrificial laminating sheet both to protect the granite and to hold the grit in place so that it will preferentially lap the stone. Based on my past experiences with SpyderCo ceramic stones I don't see any reason why that approach wouldn't work, though I expect it would take a while (and maybe a few sheets of film).

I agree with the observation that the much ballyhooed "Diamond Hardcoat Techology" in the DMT DiaFlats (and now some of the DiaSharps) isn't all it's cracked up to be. The S-II 240 isn't *that* coarse of a stone, and my Atoma #140 handles it OK.

w.r.t. the comment about flattening 8x3 stones on 8x3 diamond plates: It's very doable. The trick is to be aware of which parts of the stone tend to be under-lapped (the ends and to a lesser degree the side edges) and focus a bit of extra effort on those as you work. If you do it enough times and keep checking your work with a straightedge you'll quickly evolve a technique that works for you. I still check every stone after flattening, but I seldom have to re-lap any more.

[george wilson]

I don't know about silicon carbide,but I can tell you that ceramic grinding belts will easily grind Arkansas slip stones that have gotten broken,into new shapes. But they will not touch a ceramic stone,being ceramic also

[Patrick Chase]

I don't know about silicon carbide,but I can tell you that ceramic grinding belts will easily grind Arkansas slip stones that have gotten broken,into new shapes. But they will not touch a ceramic stone,being ceramic also

Zirconia-Alumina ceramic (ZTA) abrasives are actually pretty soft with a Vickers hardness (HV) of 15 GPa or so. Pure zirconia ceramics are softer still at ~12 GPa, but most if not all "Zirconia" belts are actually ZTA. I wouldn't expect them to do well against a synthetic ceramic stone. Their main advantage is toughness rather than hardness.

SiC comes in at about 22 GPa, which *should* be sufficient (if marginally so, which is why I said "it would take a while").

The abrasive in Ark stones is novaculite (SiO2, quartz) which comes in at about 10 GPa. For comparison pure Al-Oxide is about 17 GPa, so it isn't surprising that a Zirconium/ZTA belt would grind an Ark stone but fail miserably against a modern engineered ceramic abrasive like Spyderco.

EDIT: Corrected the HV number for ZTA above. I'd previously used the number for pure Zirconia ceramid (12 GPa per Kyocera) instead of the one for ZTA. Different sources report HV in either Pascals (N/m^2) or kgf/mm^2. To convert kgf/mm^2 to Pascals you multiply by 9.81*10^6 (and then divide by a billion to get GPa).