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Jan 6, 2010 10:56 AM

Anyone use a belt sander for sharpening knives?

I read a couple of threads on sharpening knives and didn't see any mention of using a belt sander to sharpen knives. I know if you go to most websites about making custom knives they all seem to use a belt sander to shape and sharpen the knives they are fabricating.
Well I bought a used 1 inch by 30 inch belt sander for $18 and an assortment of different grit belts to go with it for $25. It is amazing how fast one can sharpen a knife with a belt sander, less than a minute. You can start with a 220 grit for a knife in bad shape and finish it with a 1200 grit for a polished edge. The thing that slows you down is changing the belts to progressively finer grits, but if you do a whole batch using the same grit and then the next, and so forth that belt changing time becomes a minor part of the whole process. Finish up with a few swipes of a sharpening steel to remove the wire edge.
I can also use it for sharpening lawn mower blades and machetes.

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  1. Works like a charm. For ultra-fine finishing, you may want to get a leather belt to use with abrasive compounds.

    But seriously, unless you're making custom knives or sharpening professionally, it's kind of overkill. And while you're on the learning curve it's entirely too easy to ruin the temper of a blade by overheating it or to trash a tip when the belt flexes. For the typical home cook, a good set of waterstones (and maybe a jig to hold them) is probably the better bet.

    OTOH if you've got to grind the nicks out of machetes for a whole Congolese militia, the belt sander is definitely the way to go.

    1. Very cool! I only use my belt sander to put a sharp edge on my hockey stick.

      1. I cannot agree more with AlanBarnes. A belt sander is fast and efficient, but when you make a mistake you really make a mistake.

        1. It works well and is how many pro sharpeners and knife makers work.

          But your post already points out most of the major downsides of using a belt sander at home.

          1. Most home cooks don't have a need sharpen up 20 knives at once. Changing the belts takes time. This is not a problem when you have a lot of knives to sharpen, but it makes the process less convenient when only sharpening 1 or 2.

          2. The learning curve. I've seen many people write that you could ruin your knives with a whetstone if you don't know what you're doing. And when I see this, I know that whoever said it does not know how to use a whetstone, because you would have to try REALLY HARD to do any damage with one that couldn't be undone (unless the knife is single beveled, or if we're talking aesthetic damage). But a person with good intentions actually could feasibly ruin a knife with a belt sander. I wouldn't recommend trying one unless you're already decent with stones and have a couple dollar store knives to practice on.

          3. Belt sanders are problematic for some of the harder (mostly Japanese) steels that are getting popular. At this point, the hardest steel that's really common is VG-10 which should be fine, but less common steels hardened past 60 HRC can react strangely to a high speed belt sander - some get chippy, especially thin acute edges of Japanese kitchen knives. Not impossible - just harder to deal with.
          Also, those hard steels - especially when set at very acute edges as they often are - can give you a headache because of wire edge issues. They don't deburr as easily as softer steels, and because you are always using the equivalent of an edge-trailing motion, you will get some serious wire edges. Again, not impossible to deal with, just harder. Cuts into the convenience factor.

          I still think they're a great buy for someone who does A LOT of sharpening. Just not so much for someone looking to sharpen just a few knives once every few months.

          11 Replies
          1. re: cowboyardee

            Once I have all my knives sharpened after that all I use is the 1200 grit belt, so it just takes two passes which takes less than a minute to sharpen a knife. Using the very fine grits its pretty hard to ruin a knife blade unless you are trying. The tips can burn if you are not careful but there is a video that some guy made that shows a trick move you make just at the end of the pass that sharpens the tip just right. Anyway, I doubt any home sharpening machine can sharpen a tip any better than a belt sander if at all. If you need more than one or two passes to sharpen a knife either wait between passes or dip the knife in water after each pass to keep it cool.
            I never tried sharpening a Japanese three layer knife, but I don't think there is any steel harder than silicon carbide or zirconia grit. The 3M Trizack belts are really good and last a long time and have a special super uniform grit embedded all through the belt. You can even get diamond belts but they cost a small fortune.

            1. re: lazycook

              I've used a belt sander for minor reprofiling and taking out nasty chips. While you're right that it would be a somewhat hard to ruin a knife with a fine grit belt, coarser belts can easily cut an unintentional recurve into a blade without too much negligence.

              The problem with Japanese knives is not that the abrasive doesn't work or isn't hard enough. It works fine. The problems come from properties of the steel - it can be more brittle than other steel, which is a problem with high speed methods of sharpening. They can also hold onto a wire edge much more than other steels. Using a whetstone, an edge-leading or back-and-forth motion help minimize wire edge formation. That's not an option with a belt sander. There's a tendency to wind up with a wire edge that's a real PITA to get rid of compared to the knives you're used to. They are also more resistant to abrasion, which means longer passes or more passes, which in turn means more chance to ruin a temper or cut out a recurve or tear chips out of the edge.

              If you come across that video showing the trick for getting tips just right, please post a link to it. I'd like to see it.

              1. re: lazycook

                Hi Lazy,

                To answer your specific question, I have not used a belt sander for sharpening my knives. I think it is great that you get a good handle of using one. I have only used a grind wheel when I were at school and it was not on knives, just various metal stuffs for instrumential parts. My experience is the grinding wheel has only two modes: on and off. The wheel has to spin at very high speed (rpm) or the metal will get caught. At the time, I only used it when I need a good amount of metal taken off and I would polish the rest with hand tools.

                Consequently, I always think of a grinding wheel or belt sander is for serious knife reprofiling and may take off too much metal for normal kitchen knife maintance.

                Of course, I have never tried your special sand belt, so I do not really know. I am glad it is working out for you.

                1. re: Chemicalkinetics

                  I tried using my grinding wheel for sharpening knives with poor results, wouldn't try it on an expensive knife. But a belt sander is another story, so easy to use, and if you use a high quality fine grit belt there is very little chance of ruining a knife even on your first attempt. But the belt sander I am talking about is the three wheel bench models that have part of the belt unsupported by a backing plate, not the two wheel portable models one would use for sanding wood. I think a belt sander would pay for itself if you can avoid sending your knives out to be professionally sharpened, someone said they charge a dollar an inch. And if you send your knives out just the time it takes to drive to the sharpeners shop, drop off the knife, drive home, and repeat when time to pick it up is more time than you would spend sharpening half a dozen knives every month for a year. And you can put any shape or any angle on your blade you want. An assortment of medium priced knives kept sharp by sharpening them whenever they needed it would probably cut better than a collection of super expensive knives sharpened only once a year.
                  Plus you can use the belt sander for tasks like sharpening garden tools, lawn mower blades, chisels, etc. My belt sander also has a built in disk sander.
                  I would like to know what kind of machine professional knife sharpeners use, or even the factory. Every video I have ever seen on knife making they used a belt sander for sharpening the knives. I would guess a high production knife factory would have some special automated machine. I really can't see a bunch of elderly Japanese men craftsmen hand sharpening knives on a water stone. Maybe final touch-up, but not the main sharpening.

                  1. re: lazycook


                    Typically a grinding wheel is stationary, and to reprofile or putting an edge on a knife, I would move the knife toward the grinding wheel. In your case, do you clamp your knives down and hand hold your belt sander? Or do you hold the belt sander down somehow and move your knvies toward it?

                    If a professional charge you $1 per inch, then it is consider slightly below average I think, e.g. cheap.

                    Most of the Japanese knife manufactorers put the edges using a huge grinding wheel and finish one water stones. I think, but I think am correct because most Japanese knives are slightly hollow-ground on the flat side.

                    1. re: Chemicalkinetics

                      You use a bench-mount belt sander for knife sharpening, not a hand-held. See photo.

                      1. re: alanbarnes


                        Thanks. That resolved a lot of my confusion.

                    2. re: lazycook

                      lazycook, if you play the Shun promo video located on Williams-Sonoma's site, you'll see three different instances of knives being sharpened on "industrial" motorized waterstones (two horizontal wheels & one vertical wheel). They do show belt sanders being used, but only for handle shaping.

                      1. re: Eiron

                        My grandfather used to have a great big grinding wheel about three inches thick and two feet in diameter that you pumped on a foot pedal to turn. I bet that would work really good on some of these fancy knives. Don't know what happened to it. How big are the motorized waterstones, and are they flat or round?

                  2. re: lazycook

                    Hi, lazycook:

                    I sharpen on a belt machine all the time. It's a Pittsburgh-Erie "Hook-Eye"--you can find them used sometimes. Adjustable platen, bomb-proof motor, easy belt changes. If you take the end cover off, you can also do slack-belt sharpening for convex edges.

                    Here's an old knifemaker's trick that the stone pushers don't know--save your worn belts. A worn 80-grit belt sharpens like a 400, and your 1200 when worn will polish like crazy. THere are also mylar belts out there, called "micron" belts for obvious reasons. When these break, they go off like a pistol shot. Be *very* careful with these--the edges will cut you deeply before you even feel it.



                2. a belt sander it the best bet though Japenese all use waterstones. A Harbor freight is the cheapest and Leevalley sells the fine belts. One problem hone sharpeners will run into is puttting a hollow in the knife. If you try to cut with a knife with a hollow it just will not cut simply because the knife dose not meet the board fully. You have to put your knife on a cutting board or a straught edge and get your eyeball there. It can be corrected on a big beltsander but there is a learning curve which is why we profeshionals know serious cooks will have to come to us in the end if you want to get your knives sharpened

                  2 Replies
                  1. re: Rodssharpeningservice

                    Here is a link to a video on how to sharpen a knife using a belt sander. Note how quick and easy. You can also make convex edges on knives by keeping the belt a little loose so the belt bends slightly around the edge of the knife blade. There are lots of videos and articles about using a belt sander to sharpen a knife if you search for them.

                    1. re: lazycook

                      I know this an old post but I figure people will refer to it.
                      I would like to point out that a harbor freight belt sander is screaming fast. If you are using a HF sander with anything finer than eighty grit you will tend to overheat a blade past the point where you change the temper. A 1200 grit belt (probably marked 1 micron will overheat a knife in a single fast pass. I sharpened the my first few thousand knives on a wet wheel before I moved over to a viel belt grinder. Even using high end blue zirconium belts at 80 or 220 and a viel or kalamazoo slow belt grinder you have to keep that knife off the belt for long intervals to keep from cooking a blade. I keep a sponge in a tupperware of water to cool between strokes. The finer the grit of belt you use the more particles are contacting the surface makes more friction and more heat. When you see that light brown color show up you have just heated the steel to the point where you have changed the temper. That will polish out but the steel knows. Like so many things that seem so simple the more you find out the more there is to it.

                      That said. Professional knife sharpeners use belt grinders and could not do the job without them.

                      A belt grinder and a chef is a lot like a man with quarter acre lot and a chainsaw. It only takes a minute to do the job, and then he starts looking around for more trees. If you get a belt sander don't practice on your own knives. Its so good you will ruin a hundred before you even knew that you did it.