Lapping stones for flatness

One further note on the Spydie UF that I forgot to add earlier - I would originally have left mine alone as well except that I use it for straight razors occasionally. One side has been flattened and the other is still factory. The flattened side I use for razors, the factory side I use for knives.
 
Good for you. ^ That's the use I give mine. I originally purchased the fine and one side was off level. Not a lot, so I thought I'd level it and give it a finer finish. Both items I obtained. Thus, I saved 70$ by not having to purchase the ultra fine 2" X8" stone. DM
 
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MtnHawk1 said:
HeavyHanded, great info! :thumbsup:

Just one more question, if you don't mind, since I've never seen these before. Should I get the PSA (pressure sensitive adhesive) top plate so it will stick to the aluminum master lap, or do you use the non-adhesive top plate?

Thank you...
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When I bought mine they were sold as a unit, but in reality it is an aluminum blank with a PSA backed top plate on it. The top plate by itself is too flimsy, but could be stuck to just about anything flat if it is to be used by hand. $20 is a good price for a perfect fit 1/4" plate. If I were to replace it I'd get the PSA.

The 180 mesh is perfect for most stones without being overly aggressive. I don't have the 100 mesh, I use my DMT XXC if I need something more aggressive than the 180, and even still it is only a little faster and leaves a less desirable finish ( I go over it with the 180 anyway).
 
HeavyHanded, thank you for your thorough reply. Just what I wanted/needed to know! :)

Great idea, and thanks for sharing!
 
HeavyHanded said:
The 180 mesh is perfect for most stones without being overly aggressive. I don't have the 100 mesh, I use my DMT XXC if I need something more aggressive than the 180, and even still it is only a little faster and leaves a less desirable finish ( I go over it with the 180 anyway).
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Yes, I've never cared for the gouge lines left from the xx coarse DMT. The 100 grit SiC, Economy stone from ACE is about the coarsest stone I'll use. DM
 
HeavyHanded said:
Final plug for lapidary disks when it comes to lapping stones.

An 8" aluminum master and 100 or 180 mesh top disk from Kingsley North runs about 40 bucks for both and will outlast any plates made for sharpening, even if used on hard vitreous stones.

The heavy plating makes them a poor choice for sharpening, but a better choice for lapping. I wouldn't think of using a sharpening plate on a chunk of solid quartz, the lapidary plates turn it to milk.
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HeavyHanded HeavyHanded thanks for this tip! New to me for sure. I looked at the lapidary supply and saw they had 6” wheels with no arbor hole - a solid wheel of diamond available in most grits for about the same price. Do you think a 6” solid wheel would be a better choice than an 8” wheel with an arbor hole?
 
CasePeanut said:
Do you think a 6” solid wheel would be a better choice than an 8” wheel with an arbor hole?
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Yes, or at least no difference. The larger the better when it comes to lapping, my 3x10" plates do well with an 8" plate, but a 6" circle is a lot of surface area and will do a solid job on most stones. The extra 2" of an 8" stone is a lot more surface area and the arbor hole is small enough to not be a negative, but I'm confident a solid 6" will do OK for just about everything.
 
HeavyHanded said:
Yes, or at least no difference. The larger the better when it comes to lapping, my 3x10" plates do well with an 8" plate, but a 6" circle is a lot of surface area and will do a solid job on most stones. The extra 2" of an 8" stone is a lot more surface area and the arbor hole is small enough to not be a negative, but I'm confident a solid 6" will do OK for just about everything.
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thank you for the suggestion!
 
eKretz said:
That's alright. This is one of those instances where you don't know...how much you don't know. Many here have done it, myself included.
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With the 302UF, for the past days ive been (trying to) polish my Techno, the blade faces of it not the blade bevel. Originally the blade has a "stonewashed mirror" finish, basically a mirror finish which got stonewashed for christ's sake. I am still at it and it's going well. Now i am noticing that the stone surface isn't dull/matt (with the infamous pronounced machining ripples) anymore but has become shiny, i.e. pretty much reflective. Crazy. I mean, i can't see my face reflecting in the white stone but i can see a rather clear and sharp reflection of the business end of my Olight headlamp — these cold dark short winter days i wear a headlamp during my desktop work. And interestingly (but as to be expected) i can see the Spyderco machining marks now more clearly than ever .. like defects in a mirror finish; even though the ripples' height is less pronounced.

Turning a flat smooth surface from matt finish into shiny-reflective finish is an indirect proof of an improved locally flatter (and smoother) finish. I did it, and i'll keep at it because this experience is very motivating yay:cool:: my stone has become a UUF stone! ;)

The four corner areas of the rectangular stone surface are still a bit matt/dull, understandably; i can't go too near while polishing the Techno blade, trying to avoid accidental slip-offs over the sharp corners. It means that i have been dishing out the 302UF stone on a microscopic scale, that's fine :rolleyes:. It would be interesting to learn if i could make the "defects" (=Spyderco machining marks) completely disappear from the new reflective (in a sense 'mirror-like') stone finish. I could go visit manufacturers of marble sill tiles, they know how to mirror-polish marble still tiles. Then again, marble is much much much softer than the Spyerderco UF stone, so their lapping method might not work on the superhard 302UF; and btw lapping the 302UF to 'marble sill tile'-like mirror finish can't be as easy as what those marble manufacturers do .. otherwise @Sal Glesser would have done so and we wouldn't have all those massive machining marks and "non-perfect-flatness"! You're asking, why not use a "mirror polished" superflat stone from the get-go, like my Anself GREEN10000 and WHITE10000 ("Natural Agate, Emerald, White Gem"), instead of the 302UF? Because these natural stones are for mirror-polishing only and not suitable for sharpening: they don't have cutting power/properties like a ceramic stone, and with (accidentally) raised pressure and angle you'd scrape into the mirror finish, pulverizing the stone material at that spot. Look at the blade bevel and you'd see stone powder produced by your scraping bevel. While it is possible to raise a burr with those natural stones, they set you up for failure and eventual stone damage. Steer clear of buying/using/lapping such mirror-finished natural stones other than for polishing.

Back to the 302UF stone. While I do believe that lapping with an Atoma, with SiC powder (or with another 302UF stone, for that matter!) will eventually produce a superflat homogeneous ceramic stone surface, i highly doubt that such a produced surface could be called a 'UUF stone' as mine :p. The next question in line would be, what's more important: an improved-mean superflat stone (of unspecified smoothness) or an improved-ultraultrafine ceramic stone?

Long post short. Just imagine a Spyderco UF stone with the mirror finish of a marble sill tile! A 2292 dream come true :thumbsup:
 
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Not as true as you might think. The surface of a very hard hone such as the Spyderco can get too smooth and polished to do much of any cutting. This is colloquially known as "glazing" in the grinding world, and is basically excessive dulling of the peaks of the abrasive particles. This is one reason I prefer to use loose grit for finishing such a hone. Loose grit rolling during lapping/flattening preserves microscopic peaks and valleys in the surface rather than flattening the surface out like a diamond plate will do.

Mean flatness really isn't critical for knife sharpening. It's a little more critical for straight razors where you can't just change your angle a little to get the apex in contact with the hone due to the angle being preset by simultaneous contact with the edge and spine.
 
eKretz said:
can
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Yes E eKretz , "glazing" sounds like the perfect word to summarize the description of my observations. Hmm, i'd agree that the surface of my mentioned GREEN and WHITE "10000grit" chinese natural stones are "too smooth and polished" to do much of any cutting. While i understand your concerns, due to my lack of practical experience with glazed ceramic stones i can't confirm (or not yet) that my glazed Spyderco UF stone would pose sharpening problems in future. Point being, the brandnew UF surface (e.g. the bottom side of my stone!) has always been a surprisingly fast cutter to me, i raise a stubborn microburr wire edge in no time with it. The microscopic peaks of the Spyderco machining marks were mostly reponsible for the cutting action, sure i could tell. Lemme report back once i am done with the '302UF glazing project' (actually Techno blade faces polishing project:rolleyes:) and did several knife sharpenings on the UUF.

I am confident that i am gonna enjoy the performance of the glazed UF surface for pocket knife sharpening purposes, staying positive! :cool:
 
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I've also found it's a very fine line between good cutting at a UUF level on a ceramic, and 'glazing' on the same hone, in terms of how or when the effectiveness of the hone becomes substantially hindered.

I've lapped my Fallkniven DC4's ceramic side a couple or three times, the last of which approached VERY closely that threshold between a nice UF or UUF hone and a 'glazed' hone that (almost) doesn't cut well. I gauge the cutting effectiveness by wiping the surface of the hone with my fingertip or, even more telling, with a clean rag or paper towel moistened with Windex. If I still see newly-generated swarf coming off the hone in wiping it, I can have confidence it's still working OK. But if/when I start noticing the hone isn't making much swarf anymore, I start to think about resurfacing again. A lapped ceramic finished to that UUF level can deteriorate to 'fully glazed' pretty early, just in normal sharpening use. So I watch it closely over time.
 
What makes a glazed surface fundamentally problematic is that with blunted abrasive grains you're merely rubbing rather than cutting the steel. What you end up doing is burnishing your edge, and rather than effectively sharpening it you just end up weakening the steel at the apex by repeatedly pushing it back and forth.
 
I did my Spyderco F both sides, managed to glaze it to the point it was only good for burnishing - basically a smooth steel.

Went back and ground lengthwise lines it with coarse and medium diamond plates on opposing sides. Works OK. I don't recommend working them with anything but diamond.
 
Using loose lapidary diamond grit (just takes a little!) on plate glass works MANY times faster than using a diamond plate and gives a more uniform finish. Works very nice, even on extra hard materials like sintered silicon carbide.
 
HeavyHanded said:
I did my Spyderco F both sides, managed to glaze it to the point it was only good for burnishing - basically a smooth steel.
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Guys, literally by accident i discovered ("invented") a new stropping technique for our repertoire!

How to do:
  1. Sprinkle a few tiny crumbs of your (fast-cutting!) solid polishing compound on the glazed UF benchstone ("302UUF"). Or simply rub the solid compound directly onto that stone surface.
  2. With a tiny dab (less than a droplet!) of oil on your finger, dissolve/rub/disperse the wax-based compound evenly on the entire surface. A shiny surface means that there is too much oil or not enough compound; the loaded surface should look matt white (because the stone is white).
  3. Now use this loaded stone as your new benchstrop! Basically you're stropping on an abrasive "cream".
The key for this technique to work is that you use a solid polishing compound which is fast-cutting (for example my kwb BLUE, kwb WHITE, or MERARD compounds); swipe your blade bevel 1x across your block of compound and you'll see if the compound is fast-cutting ;). Diamond pastes don't work here, and a different smooth hard diy carrier like a sheet of window glass wouldn't do the trick either, i guess; a mint 302F should work, though. The micropores of the Spyderco ceramic stone seem to hold the cream nicely for our purpose. (Once you're done stropping, say after 5min, the loaded UUF surface will look black! Rub 3 drops of oil on the surface to lift the cream out of the pores and wipe the stone clean with 1 sheet of toilet paper. Done.)

I got amazing stropping results with my biggish ZWILLING chef knife which has a fairly straight edge and hence is rather easy to strop on a benchstrop. The smaller the knife, the shorter the blade, the bellier its shape, the more inconvenient, unnatural, and impossible becomes such a 'zero-give' benchstrop as the chosen stropping method. So i can recommend this creamy UUF benchstrop method only for stropping (or deburring) common chef knives or santoku knives, not for pocket/EDC knives. Counter-example, the very best method for maintaining the exotic Fox Suru blade are still freehand sharpening thru 204-freehanding and freehand deburring with loaded paint stirring staff strops.
 
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