Lapping stones for flatness

Diemaker said:
Once you try lapping with loose abrasive you will understand. It is something words alone can not convey.
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I second this. Ever use a waterstone to sharpen? Same principle of how a waterstone slurry eats steel fast is what is going on.
 
I get my stuff from Ken Schwartz. The flattener I have is roughly 3x9 inches. It's made from "toothy metal." I take the stone and make three, large "Xs" in pencil lead. I then make several asymmetrical passes on the flattener, the first passes make a long slender oval mark.

When I think I'm done I hold the stone portion against a solid metal container and look for bits of light appearing mid-stone.
 
kreisler, I did my Spyderco ceramic fine stone with just the coarse & fine diamond. And I would not take it any finer. As it will begin to glaze. DM
 
I'll wait with the SiC powder method.
Thanks for the concern/advice David Martin David Martin , i should have some DMT lapping results after the weekend. Today i have sore muscles from the sandpaper lapping method omg haha.
 
kreisler said:
I'll wait with the SiC powder method.
Thanks for the concern/advice David Martin David Martin , i should have some DMT lapping results after the weekend. Today i have sore muscles from the sandpaper lapping method omg haha.
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You'll be a quarter as sore or less using the loose abrasive method. Just sayin'. :) For surface conditioning a diamond plate works fine, but for gross flattening of a sintered abrasive you're gonna' murder yourself trying to use coated abrasives. It only gets more difficult the flatter it gets, since the larger surface area spreads out the force.
 
K kreisler :p ;) :D

You don't need a kilogram of each grit. I am not supposed to post product links but there are many affordable options on eBay, Amazon, etc., as well as dedicated rock shops. Email me at the address at the bottom of the GLGC if you need some help.
 
Spideyjg said:
Ever use a waterstone to sharpen? Same principle of how a waterstone slurry eats steel fast is what is going on.
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I do not believe the mechanism is the same. On a stone the slurry causes continual refreshing of its surface, exposing new abrasive, which is what "eats steel."
 
Getting down into the weeds, the physics likely is not identical.

However to describe what lapping on grit feels and grinds like it is a good analogy.
 
kreisler said:
Stay tuned for updates on my progress with this Spyderco ceramics lapping project :thumbsup:
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I had finished the project at that time but didn't update the post. Sorry for the late concluding thoughts, my observations and opinion:
  • the low grit sandpaper P360 speeds up the mean-flattening process yes and, as many practitioners have "observed" with bewilderment, the resulting white finish "looks and feels as fine & smooth" as if the ceramics had been mean-flattened with a high grit sandpaper P2000. however, the impression of fineness & smoothness originates from the perfect mean-flatness of the finish and not from the fineness of the finish! in reality, with a magnifying glass, one can see that the P360 leaves a "more porous" mean-flat surface behind whereas the P2000 leaves the original "less porous" mean-flat surface intact. For your better understanding, think of swiss cheese of a similar type A and a cheese slicing machine. CheeseA1 und cheeseA2 weigh the same (each 500g) but have different volumes (volA1 < volA2) because cheeseA2 has more and bigger holes (air pockets) inside. When you slice either cheese with a machine, all produced surfaces of the cheese will be equally mean-flat and fine & smooth because they were produced by the same sharp rotary cutting blade. But it is obvious that a slice of cheeseA2 looks more porous at the surface than cheeseA1. The original material of 302UF is nice and dense, with tiny pores. Treating the 302UF with P360 produces a mean-flat smooth (and "fine") surface with surficial bigger pores, similarly to the surface difference between a mean-flat smooth slice of cheeseA1 vs cheeseA2. Does it matter? I dunno. Just saying. My recommendation: do not treat your 302UF with a low grit sandpaper.
  • Yes, the longer you treat the ceramics with a fine sandpaper, rubbing and rubbing, the more you produce a glazed ceramic finish. Uber-smooth surface. A ceramic surface so smooth that it doesn't cut anymore, think of window glass or a mirror. My recommendation: do not over treat your 302UF with a high grit sandpaper.
  • Yes, due to various minimal physical, technical, mechanical, practical effects/realities/phenomena, imperfections in the process (which i can't explain), sanding will produce a reasonably/usably mean-flat surface but not a geometrically 100.0000% mean-flat one. We only choose sanding because we doht want to afford the expenses of a truing stone or diamond plates. My recommendation: do not treat your 302UF with sandpaper.
  • My sandpaper-treated fully glazed 302UF (= sideA) doesn't cut, or it cuts tooo finely, such that i use it for mirror-polishing purposes only. Not for sharpening. However it is not the best for mirror-polishing either because of the dreaded mirror-polishing side effects (micropitting; burnishing; …). Oh well, maybe i should have followed my recommendations and not have treated the ceramic stone with sandpaper at all omg lol.
  • Fortunately i treated only one side with sandpaper. I treated the other side (= sideB) with a DMT product (DuoSharp Bench Stone FINE/X-FINE), and that worked out very well. The produced surface is super dense ("cheeseA1"), super fine & super smooth, 100.0% mean-flat, and still cuts. All spiderco grinding marks are gone! SideB is now deserving of the label "UltraFine" :cool:, and definitely an improvement imho over the original 302UF finish. I must admit though that i haven't used sideB and sideA very much since i finished the modding project because i got a better ceramic stone than that ;). On a side note, the DMT product is toast by now lol. Maybe i had used too much pressure. Be it as it may, using a DMT product to lap your ceramic bench stones does work but the lapping process will degrade/ruin the DMT product, sooner than later. Think of it, diamond is harder than ceramics; diamond is embedded in metal; ceramics is harder than metal; who emerges as survivor after a while? :rolleyes: (solution: if you kept lapping and lapping, the metal would eventually lose the diamonds, then the ceramics would start consuming the metal, and in the end nothing is left but the ceramics :p)
Summary: better doht use sandpaper to lap your ceramic stones; it is not the way to go imho (i'm the original el cheapo, so i wanted to try that convenient and cheap path first). DMT products can be used for lapping ceramic stones (and to fantastic effect and end result tbh!) but that reduces the lifetime of the DMT product by much. very much. my 302UF is now a unique jewel to me, priceless, since i spent so much energy, time, efforts, expenses, and frustration, on the modding. it has two differently performing sides (sideA vs sideB) now, both very different to the original 302UF performance. if i could turn back the clock 6074, i'd most likely leave the original 302UF unmodded, not bother any further, and get the better ceramic stone instead. I pretty much doht use my modded 302UF stone anymore but i wouldn't sell it either. :thumbsup:
 
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