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Knife sharpening for a practical guy

Discussion in 'Maintenance, Tinkering & Embellishment' started by Fass, Mar 8, 2020.

  1. Fass

    Fass

    10
    Mar 8, 2020
    My first post here :)
    I am thinking about buying my very first pocket knife for EDC use, think simple tasks like opening boxes, cutting rope, slicing an apple etc. The knives I am looking at are simple droppoint slip joint models like the one my granpa used to carry or a SAK.

    Since I am really a practical guy, this knife will be a 'users knife' so it needs to be of good quality and most importantly, it needs to be sharp and capable of easy and fast resharpening without the need of having to buy extra (expensive) tools. Though I respect everyone's hobby, I am not the sort of type willing to spend a lot of money on stones, strops, honing paste etc. etc.

    Do you have any advise on how I got go about easy DIY sharpening with stuff that I have already laying around the house? Think sandpaper, a coffee mug etc. I really want to learn how to sharpen a knife the old fashioned way like my grandpa probably would have done it. Any tips, best practices etc. are very welcome. Thanks!
     
  2. Mr.Wizard

    Mr.Wizard

    Feb 28, 2015
    If these apply:
    • you don't need crisp, flat bevels, and it's OK to scratch the blade
    • a "working edge" will do; you aren't chasing hair whittling or hanging-hair tests
    • you are working with steel that grinds easily and doesn't form large burrs
    It can actually be pretty simple. (Simple, but not entirely easy; you still need to practice.) Shape and thin the edge on something medium-coarse, keeping the angle low with every pass. If we assume you have a ±5° wobble you want to do this shaping at 5° to 15° (per side), not 15° to 25° for example. Work from both sides until you reach the apex all along the edge, which you can detect by feeling for a burr or looking for the absence reflection from light shined directly onto the edge. Work in sections as needed. Now switch to your fine stone or equivalent, and make very careful, very light passes at a slightly higher angle than any of the shaping, say 20° (per side). If you are using a smooth, hard finishing stone like the bottom rim of a coffee cup try these passes edge-leading, like you are trying to shave the stone. If you are using something softer or less smooth try these edge-trailing. Check for sharpness after every pass or two.

    If your blade is thick and needs a lot of work to thin/shape the edge then you will want three steps, coarse, medium, and fine. Ideally get close to the apex with the coarse without actually forming a burr, but it's OK if you do. Finish the shaping at the same low angle using the medium stone, before making the higher angle finishing passes. "Coarse" here means something like 80 to 120 grit wet/dry sandpaper. If you have a lot of metal to remove and try to do it with something too fine you'll probably get frustrated and raise the angle.
     
    Last edited: Mar 8, 2020
  3. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    Read the sticky "Seven secrets of sharpening" and get a two sided bench stone.
    You could use wet/dry sandpaper as well, but the combo stone is a solid value and about as practical as it gets.
     
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  4. For typical traditional slipjoint knives like SAKs, you'll NEVER need anything coarser than maybe ~220 grit or so. Small, thin blades like these, in basic carbon or low-alloy stainless steels, will still grind, shape and sharpen up quickly with anything in the 220-400 grit ballpark. Anything coarser will remove much more steel than necessary and will also necessitate a lot of 'clean-up' sharpening to reduce or refine the too-coarse scratches and ragged edge left by low-grit grinding. A 320-400 grit finish also makes for a great working edge in steels of this type.

    For sandpaper, wet/dry type in silicon carbide (SiC) works pretty well in the range mentioned above.

    With a light touch, even some types of emery boards of the black or pink type can maintain or even create decent working edges. Bevels will be somewhat convex coming off of these, as their foam backing makes them a bit soft for crisp, flat bevels. But it works, as I've done this before and can attest to it's usefulness in a pinch. Use these edge-trailing, as with sandpaper or stropping.

    I'd still suggest acquiring a simple small hone or stone. A fine India stone (~320-360) in a portable or pocket-sized version works very well with knives like these (it's currently my first choice for steels of this variety). Use the stone with some lubrication like mineral oil, to keep it clog-free and cutting efficiently. For a more all-inclusive, all-capable hone for any steel type, a Fine or EF (600 - 1200) diamond hone can work very well and very quickly, used with a very light touch. I like using such a hone for my Victorinox paring knives, for example, in the same steel as their SAK models. The grit ratings for diamond hones seem high, but diamond will cut very aggressively as compared to the India. The 600-grit diamond will leave a scratch pattern at least as coarse, if not more coarse than the Fine India, with the EF diamond (1200) leaving a finish that's maybe just a hair finer than the Fine India.

    I suggest keeping at least one reputable, known-good hone/stone simply because, with other improvised means like coffee mugs, etc., sometimes there'll be a lot of variability in how those perform as measured against expectations. If one particular mug or whatever doesn't quite live up to expectations, the Fine India or the Fine/EF diamond can quickly fix it. ;)
     
    Last edited: Mar 8, 2020
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  5. tonymp

    tonymp

    129
    Jun 15, 2014
    slip joint Spyderco, or even the buck 110 or 112 lock back, that's what my grand farther carried, the steel on buck 110 or 112 is fairly easy to sharpen (unless you get it sv30), I've got sharp knives using the bottom of a coffee cup or a bowl but I also have dulled knives using those things, with a Spyderco double stuff, you can keep a knife sharp for a very long time, that's pretty simple.
     
    Last edited: Mar 8, 2020
  6. Papilio

    Papilio

    55
    Sep 6, 2019
    You can't go wrong with a SAK. Sharp, durable, easy to sharpen, many choices.
    For sharpening with DIY / household items...have you ever heard about Chris Lubkemann? He is an expert woodcarver with decades of experience. He uses pocket knives for whittling, his preferred knives are SAKs. And he sharpens his knives with sandpaper (wet-and-dry) or - a little bit more expensive - emery tape. And for stropping - if you want to go that far - and old leather belt, glued to a piece of wood - with stropping compound from a hardware store. Will cost you a few bucks and lasts a long time.
    If you keep your blades sharp, you probably don't need a coarse grit for a long time.
    You can learn about his method on Youtube:
    Part 1

    Part 2

    Third one (Fox Chapel)


    I do not agree that sandpaper will get finer the more used it is. Well, the more worn out it is the less aggressive it will be. But anyway. It is a simple and cheap method.

    In his books his method is explained, too. In detail:
    - One old double-sided whetstone (coarse grit, no exact grit mentioned)
    - wet-and-dry sandpaper (320, 400 and 600)
    - piece of wood as a sanding block (pad for the sandpaper)
    - leather (piece of an old belt) and some honing compound.

    Maybe that's what you are looking for?
    But keep in mind: Sharpening on sandpaper (as well as on a strop) you do not push your knife with the edge but the back / spine ahead. Otherwise you could cut into the sandpaper.
     
  7. jpm2

    jpm2

    Nov 19, 2014
    I don't ever recall seeing my Dad sharpen on anything other than silicon carbide sandpaper.
    He always used 400 grit laid on the edge of a table.

    I have what used to be 400 grit sandpaper. It now produces a naked eye polish on any metal. It's 3M 405N paper A wt. open coat.
     
  8. Papilio

    Papilio

    55
    Sep 6, 2019
    Cool. I really like those cheap and easy methods.

    Interesting.
    What I meant is in the video he talks about a 400 grit sandpaper that has become more and more worn out and now is like a 5.000. The subtitles say "5.000 grit" but the sandpaper won't get more abrasive particles just because it wears out. So the keyword is probably "feels like". But I agree that it can feel a lot finer after some use.
    So better buy quality like 3M.
     
  9. Wet/dry sandpaper, most of which is in silicon carbide grit, WILL effectively get finer with use. This is due both to the paper clogging, AND to the fact that the SiC abrasive is friable (meaning it actually DOES break down into smaller fragments, because SiC is a relatively brittle material, like glass). So, with SiC sandpaper, the grit actually does get finer with use.

    This is also seen with loose SiC grit used for lapping purposes. As it's used, it must be frequently replenished with fresh material, because the working grit breaks down into smaller particles, reducing aggressiveness and also producing a finer finish.

    Other sandpapers in aluminum oxide or garnet, etc., won't break down as much as SiC does, because they're tougher (less prone to brittle fracture) and therefore less friable than SiC. Most of the wear with those happens due to dulling of the grit particles' sharp edges with use.
     
    Last edited: Mar 9, 2020
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  10. ToddS

    ToddS Basic Member Basic Member

    390
    Jan 15, 2015
    I don't believe it's likely that grit is fracturing in fine sandpaper - the backing is too soft to "push back" against the force of the blade. Although it definitely can happen with coarse grit.
    What you are observing is that the "proud" grit particles are knocked out (fairly quickly) leaving only particles that are submerged below the resin with just the tips protruding as the blade passes over.
     
  11. Even the manufacturers of SiC sandpaper point out the grit's brittleness and friability as a factor affecting durability and finish, as compared to other abrasive types. It's a long-known and proven characteristic of those sandpapers. I'm sure some grit does also tear out of the backing. But the difference in durability and finish can be seen when comparing it to AlOx abrasives using the same type of paper backing. AlOx grit will also tear out of the backing, but the finish doesn't trend finer as noticeably with AlOx papers, as happens with SiC sandpapers by comparison.

    Mfrs also refer to SiC's 'self-sharpening' characteristic in use, which means it's breaking down to create new, sharp cutting edges, and by extension of that, becoming smaller as it works.
     
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  12. Mr.Wizard

    Mr.Wizard

    Feb 28, 2015
    Hypothesis: the initial grains of SiC that come loose roll around the surface smashing up other grains which in turn continue the process.
     
  13. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    There is a pressure component with SiC wet/dry, if you use too light of a touch the life of the paper suffers and it loads more rapidly. On my Washboards you would expect the paper to wear out faster due to the smaller contact area, but the opposite is true.

    The greater pressure improves the refresh rate and also improves the consistency of the grinding finish right to the end. There is a fair amount of science that goes into backings, adhesive layers etc to make a given type of sandpaper work well.

    There is an initial break in period but after that it should be pretty consistent. On the better papers, the break in period is very short.
     
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  14. Some sandpaper mfrs describe the grains of SiC used as thin/narrow and shard-like. This shape is also an aspect of why it cuts very aggressively when fresh, but is also more prone to snapping/breaking when lateral stresses are applied across the narrow dimension of the grains. Even some wood-sanding applications are known to cause the grains to break down pretty rapidly. And in metal-finishing applications, it's also part of the reason why SiC has a good reputation for high-polish finishing, because it continually breaks down to smaller sizes while still maintaining sharp cutting edges. This means it still cuts aggressively for it's size, while the decreasing size of the particle itself limits the depth to which it cuts, to a finer and finer degree.
     
    Last edited: Mar 10, 2020
  15. Papilio

    Papilio

    55
    Sep 6, 2019
    Very interesting. Every time I visit this forum I learn something new.
    Lesson of the week: Check.

    @Fass:
    As I have written above Mr. Lubkemann uses 320, 400 and 600 grit. But because he has some worn out pieces it is much finer then.
    So either use worn out sandpaper, too. Or buy a new piece with a finer grit? Depends on how sharp you want your blades and what you are going do do.
    A coffee mug is ok for improvised sharpening. But I wouldn't use it as a regular device. There are better options like sandpaper. Because your mug could be rough or finer, you don't know.
    A coarse grit will take away more material from your balde than finer grit does. Using sandpaper gives you more control what you are doing, depending on the condition of your blade, whether it only needs a little touch up or is rather dull.
     

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