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Thread: I have a sharpening question ....

  1. #1
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    I have a sharpening question ....

    Oh groan .. another bloody sharpening thread. Well, perhaps this has a more practical goal.

    Fred asked a question (in another thread - I did not wish to sidetrack that) regarding the grit of the Shapton diamond dressing plate (which is 275 as I recall. I have one). What this reminded me of was a question I have been meaning to ask for some time regarding the grit of a dressing plate.

    First off, we use stones (water-, iron- and diamond) of a range of grits to hone plane and chisel blades, usually starting around 1000 and ending north of 8000. Sometimes up to 50K. In waterstones I have Shapton 1000, Sigma 6000 and 13000. I am not sure what the Spyderco ceremanic stones are rated at. It does not matter.

    The issue is 'what does it matter what grit we use to dress a stone?'. Does it make a difference to the results from (say) a polishing stone (8000 or 13000 grit) if the dressing stone is 275 grit or 600 grit? In other words, can the structure of a sharpening stone be altered by the grit of a dressing stone?

    Is this the same as using a stone which has grooves - would it make any difference whether the stone is smooth or pockmarked? Logic says to me that grit is grit, and that surface conditions do not matter.

    However, I am reminded that the Tormek has a wheel that is 220 grit. It can be "regraded" to 1000 by using a dressing stone. No doubt this works so by a crushing action on the surface of the wheel, which reduces the 220 to 1000 particle size. Yes, no? But is this the same thing as a diamond dressing stone being run across the surface. Surely it is not crushing the grit. It may create larger or smaller mini "furrows" but these should not alter the grit, per se.

    A second, related question ...

    I read of warnings that dressing a polishing stone (e.g. Spyderco Ultra Fine, or a natural oilstone, such as a Hard Black Arkansas) will release fresher grit, and the stone will not polish as well as beforehand. To me, that is like saying the constant pressure of sharpening a blade crushes the grip, creating finer grit. However, the stone cannot remain this way since the surface becomes glazed and will not cut. What is better, a dedicated stone for a specific task that is dressed frequently for ultimate cutting action, or one that works at a higher grit than intended by nature, but do so slowly? If the latter was supported (I shudder!), then we would all have a series of dressing plates ranging from 275 through 6000+ grit just to avoid hampering the potential of the polishing stone.

    Regards from Perth

    Derek

  2. #2
    Derek,

    I don't think I have noticed any difference in performance.

    For many years I flattened all stones, 800 to 15,000 with 240grit wet and dry.

    Recently I have used Diaflat, very coarse, and Shapton diamond fairly fine, without noticing any difference.

    As you know my sharpening method only uses three or four strokes to polish edge, so there is not much opportunity to compare feel!

    Backs of chisels do not seem to change.

    Best wishes,
    David

  3. #3
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    It absolutely makes a difference, but whether or not it matters depends on how quickly your stone wears back down to its "natural" grit.

    For man-made Japanese water-stones that wear very quickly, there is nothing to fear about using a coarser stone to flatten them, because they will wear to their natural grit very quickly. It's a completely different story with stones that wear much more slowly, though, such as Arkansas or India stones.

    Here's my experience with oilstones:
    India:
    - I lapped my fine India with a well worn "600" grit diamond plate, and found it cut very slowly after that. I refreshed it with a worn in 300-grit plate, and it was back to normal; cutting quickly, and still leaving a fairly good edge for its grit. It does not appear to wear down much finer than this (400ish?) in normal use.
    Soft Ark:
    - For my Soft Arkansas, I find that I need to refresh the surface every few times I sharpen if I want to keep it cutting quickly. I use 400 or 600 grit for this usually. If I let the stone settle in, it will graduate to somewhere in the neighborhood of 1000-2000 "grit" over time. So, essentially, I'm keeping it much coarser than it naturally is. After one or two uses, it quickly starts to approach its natural grit.
    Hard Ark:
    - For my Hard Arkansas, I've found that it has worn in to somewhere around 4000+ grit less quickly. It actually cuts finer than my translucent Arkansas currently. More on that in just a second. It took about a week or two to wear in fully. I have not lapped it and will avoid doing so until it needs flattening, if it ever does.
    Translucent Ark:
    - My Translucent Arkansas is taking quite a while to wear in. It's about equal to my Hard Ark currently, but one side I tried to lap with 2500 grit sandpaper to wear it in, and I wound up making it coarser instead. That side has remained coarse, showing very slow wear. So, for very wear resistant stones such as this, or an India, lapping with too low a grit will definitely make it cut coarsely for a while. After 3 weeks of use, I'm just starting to find that my Translucent is close to, or passing my Hard Ark in fine-ness.

    So, my Soft Ark wears in the quickest, followed by the Hard, and lastly, the Translucent, which appears to wear in much more slowly than the other two. So, it depends on the hardness/wear resistance of your stone for sure. For natural stones in the harder range, or for India stones and such, I would recommend lapping close to the grit you want to end at, or else just be willing to wait a few weeks for it to wear back into its natural grit. However, also be aware that you can over-polish coarser stones and make them cut more slowly by the same token.

    All that said, I'm quite new to this. This is just my experience so far, playing with my oil-stones over the course of a few months. The interesting thing about the natural stones in particular is that how they cut is very much up to you; how often you dress them, what grit you use when you do, and how clean you keep them.

    I'm almost willing to bet that if I lap the already coarser side of my translucent with a 300 grit diamond plate, I'll have a very useable coarse/medium grit stone that will cut quickly, and stay that way for a while -- perhaps even better than my soft arkansas. I'm almost tempted to try this.
    Last edited by Luke Dupont; 08-23-2016 at 3:07 AM.

  4. #4
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    Hi Derek, the following is more specific to the use of Japanese Natural Stones, but it does has some relevance to the topic you've raised. http://classicedge.ca/index.php?rout...ry&path=72_100

    Stewie;

  5. #5
    Like Luke, I'd say that it doesn't matter for manmade waterstones, they release grit so easilly that any difference in the surface from coarser or finer dressing stones quickly disappears. I've always flattened my waterstones from 400 to 8000 with the same extra extra coarse DMT. Now I use oilstones I refrain from flattening, so I can't really tell from experience. Oilstones are a lot more complex though. Here you are changing the shape of the grit through use. I suppose the shape of the grit also changes when you are rubbing an abrassive over it, I don't think that really creates sharp grit particles, you are just removing the top layer and any build up crud.

    I haven't found glazing to be a problem yet, allthough you could say that technically speaking my vintage Norton Translucent is glazed, but it still cuts, creates a wire edge and the steel leaves black smudges on the stone. This stone hasn't been dressed in ages.

  6. #6
    I notice this before.

    Run a 320 grit on a Shapton Pro 120 grit. Grind a blade on it. Now run a 800 grit on the Shapton Pro 120 grit stone. Grind the blade again. There is a difference in cutting speed.
    But the man made stones due breaking down quickly though.

  7. #7
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    Quote Originally Posted by Kees Heiden View Post
    Like Luke, I'd say that it doesn't matter for manmade waterstones, they release grit so easilly that any difference in the surface from coarser or finer dressing stones quickly disappears. I've always flattened my waterstones from 400 to 8000 with the same extra extra coarse DMT. Now I use oilstones I refrain from flattening, so I can't really tell from experience. Oilstones are a lot more complex though. Here you are changing the shape of the grit through use. I suppose the shape of the grit also changes when you are rubbing an abrassive over it, I don't think that really creates sharp grit particles, you are just removing the top layer and any build up crud.

    I haven't found glazing to be a problem yet, allthough you could say that technically speaking my vintage Norton Translucent is glazed, but it still cuts, creates a wire edge and the steel leaves black smudges on the stone. This stone hasn't been dressed in ages.
    I haven't found any trouble with glazing either. But then, I use oil and always add a little more at the end and rub the stone to lift the shavings out, wipe it down, and wash it with hot water and soap on a semi regular basis. The one time I did have glazing happen is when I was first messing around with a cheap soft ark, and used water instead of oil. It quickly clogged and glazed over. So, it seems more a problem of not using an appropriate lubricant and/or not keeping your stone clean. I've also only been using arks for about 5-6 months now, so perhaps it's too early for me to comment.

  8. #8
    Just information - Im not sure how to interpret it yet, but with luck this thread will help. ...... For the Shaptons, their web site (shapton-usa) says their lapping plate is for flattening Shapton stones from 500 grit to 30000 grit. They also say not to use it on water stones coarser than 1000 grit if they are made by other companies, but dont say why.



  9. #9
    Maybe because coarse stones can be very hard on diamond plates and they just want to play safe.

  10. #10
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    It makes a difference. In rougher stones, which release new particles quickly, the practical difference is insignificant, as others have pointed out.

    In the case of finer stones which do no not release fresh particles quickly, and which see much less use, dressing with a rougher stone often results in the finer stone being effectively rougher in grit for a time, perhaps equal to the number of strokes required to normally finish a plane blade. This is irritating.

    Another problem is that the grit from a rougher stone used to dress a finer grit stone can become embedded in the finer stone. This is a real problem. The same things happens on dusty days. Get out a loupe and check the scratches and you will see the difference.

    On the other hand, I have been called an idiot for not knowing that one MUST use a rough stone to dress a hard chert novaculite stone to keep it useful.

    Who wudda thunk it.

  11. #11
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    I use a 1200 Atoma on natural finish stones, which for me are Yaginoshima Asagi, Shinden Suita and Nakayama Asagi. They're all higher than 6000 grit. My logic being that I do not want to wear out the stone at an excessive rate and I want to build a light slurry not a heavy slurry. It also helps to keep the stone flat.

    I use a 400 Atoma on the Tsushima nagura (2000-3000)

    120 Atoma on the soft Ark (1k?)

    120 Atoma on all synthetic stones, which include india stones and all ceramic water stones.
    Bumbling forward into the unknown.

  12. #12
    I haven't been using water when I flatten water stones (Naniwa) on my diamond plate . Instead of getting clumps of loose waterstone material that needs to washed away, I get a fine dust that I can brush away or suck up. I also don't have problems with the stone sticking to the plate. If I'm flattening a bunch of stones, I start at the finest and work my way down, that way I'm not embedding coarse grit in the finer stones. I give the diamond (Dia-Flat) plate a thorough was when I'm done.

    So far this method has worked very well for me and the diamond plate is holding up. Has anyone else tried it?

  13. #13
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    You guys are talking about things I have no idea about. I use diamond hones and leather charged with honing compound. They stay out on the bench and if an edge needs help I do it instantly and continue what I'm doing. It's a habit I picked up from Paul Sellers.

  14. #14
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    Quote Originally Posted by Derek Cohen View Post

    The issue is 'what does it matter what grit we use to dress a stone?'. Does it make a difference to the results from (say) a polishing stone (8000 or 13000 grit) if the dressing stone is 275 grit or 600 grit? In other words, can the structure of a sharpening stone be altered by the grit of a dressing stone?

    Is this the same as using a stone which has grooves - would it make any difference whether the stone is smooth or pockmarked? Logic says to me that grit is grit, and that surface conditions do not matter.



    Regards from Perth

    Derek
    I have two thoughts, that are more of an opinion.

    The first, if you are dressing a stone. Wouldn't you expect to see a scratch pattern on the stone, much like the scratch pattern you see on the steel you are trying to sharpen. When I am sharpening something say a plane iron, I watch the scratch pattern. Then move to a finer stone. On the next stone, remove the scratch pattern from the previous stone. Keep doing that until I get the level of polish I want.
    So If you used a courser grit to flatten a stone, would't you expect a scratch in the stone? Does that scratch pattern transfer to the iron you are trying to sharpen. I don't know how you could tell without a microscope.

    The second thought is if you use a grit that is too course, how much does it shorten the life of the stone. Think about it like a piece of wood with a and sand paper. Use a course sand paper and you will remove more material than you would using fine sand paper.

    Without some kind of scientific equipment it is almost impossible judge what happens when you flatten a stone. I would guess the companies that make and sell the stones have tested for this, and have the answers.

  15. #15
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    I doubt there is very little difference beyond the first several passes on a freshly surfaced stone. The coarseness of the surface may briefly effect the efficacy of the honing action, but the grain size of the abrasive is unaffected. I suspect that a freshly honed surface may generate a slurry faster and the toothed may temporarily create voids for swarf to collect and channel away from the cutting surface, also exposing more fresh grit surface. This might result in a temporarily more aggressive, courser surface finish.
    My only analog is dressing stone wheels for glass engraving. For course cutting dressing is done more frequently to expose fresh abrasive, however one avoids dressing smoothing wheels and allows the surface to "glass up" over weeks or months the result is much slower cutting, but a much finer and glossier finish.
    "Aus so krummem Holze, als woraus der Mensch gemacht ist, kann nichts ganz Gerades gezimmert werden."

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