Knife Sharpener-Following the Right Sharpening Process

by Karen N

Just with any other cutting and slicing tools, the blades of a knife can become dull over time. Too much dullness can render this tool next to useless. To bring back the sharpness of this tool, a knife sharpener is used. While sharpening is usually thought of as a one-step process of just grinding the blades against a hard rough surface, careless sharpening can lead to damage. Damage is highly undesirable especially if the knife is an expensive make.

The knife sharpening process

Beyond knife sharpening, the whole process involves two extra stages which are equally important as the first stage. The first step involves the sharpening process, which is basically the removal of metal so that a new edge is formed. This step proceeds from rough to fine sharpening. For rough sharpening, various knife sharpeners may be used such as water stones and oil stones. For fine sharpening, similar sharpeners are used but those with finer grits are chosen.

Subjecting the blade to rough use can make the edges crooked and bent; hence, the straightening process follows after sharpening. The existing metal on the blade is carefully straightened so that small quantities of metal are removed. The preceding processes make the knife sharp once again. However, the edges can easily accumulate foreign particles if not polished. The last step involves stropping, which polishes the edge to give it a mirror finish without altering the edge significantly.

Types of sharpeners

knife sharpener must be harder than the base metal or steel used in knife edges. The most preferred type of knife sharpener is the diamond stone sharpener. Diamond, being the hardest stone, is several times harder than ordinary metal; hence, it offers better control in sharpening the edge. The diamond type is, however, expensive. To reduce the cost, composite materials are used. In the composite type, a metal base is covered by a layer of diamond. This layer is chemically bonded to the metal surface to provide greater strength.

The less expensive type of sharpeners is made from natural stones, which are hard enough to provide a sharpening effect but may easily wear through continuous usage. Among the natural stone sharpeners, the genuine silica known as Novaculite is the most-sought variety for its commendable abrasive properties.

Sharpening wet or dry

Diamond and natural stone sharpeners can be used either in a wet or dry abrasion procedure. Subject to the availability of a sharpening fluid, wet sharpening is recommended since it constantly keeps the pores of the sharpener clean from discarded metal particles. Dry sharpening, on the other hand, is carried out on a dry sharpener surface and cleanup is only performed as needed. Dry sharpening, however, can encourage frictional heat which is undesired especially for fine polishing.

The sharpening fluid is preferably water-based, since petroleum-based fluids can result to unexpected chemical reactions with the metal surface. Water-based honing oil is highly recommended. If this type of fluid is not available, then plain water may be used instead. When using natural stone sharpeners, the abrasive surface is easily scratched off by the blade of the knife. As soon as the fluid pool gets murky, the fluid must be replaced.

Sharpening process for straight blades

Straight or non-serrated blades are the most common knife edges. Before proceeding to any sharpening activity, the blades must be examined first by holding the knife with its edge facing up. Looking along the length of the blade, visible flat spots or nicks can be easily observed. If it is nicked and extremely dull, then the process begins with coarse grit sharpening. If the blade has no visible nick but is obviously dull, then coarse grit sharpening may be skipped and the process begins with medium grit sharpening. If it is just slightly dull, then fine grit sharpening is the only step that is needed.

Coarse grit sharpening is applied to dull and inconsistent blades with visible nicks and extremely dull spots. This step is referred to as the rough cut due to the amount of metal that will be discarded from the original edge. In coarse grit sharpening, the knife is held perpendicular to the abrasive surface to make the edge even. After the edge is even, the knife is held at an angle of 13 to 16 degrees with the abrasive surface and the grinding process is again performed. This coarse grit sharpening process prepares the knife for the medium grit sharpener.

After the rough cut, the knife is sharpened against a medium grit surface. In this stage, careful control of the knife must be observed. The honing stroke must be light and performed from one side to the other and vice versa. The process is finished until the no burr is felt from both sides of the edge.

Finally, the fine knife sharpener is used to fine-tune the sharpened edge. For this stage, natural fine stones are recommended so that minimal abrasion is applied on the blade. Generous amounts of sharpening fluid must be used during this final step.

Comments

  1. Jesse Mathewson says:

    Good information!

  2. JP in MT says:

    I grew up hearing “more people are hurt with dull knives than sharp ones.” I have also learned that a cut from a sharp knife heals quicker.

    I’m still amazed at the people at the gun shows, who will pick up a knife and “test the edge”. And there’s the ones who get mad if you stop their kid from picking on up off the table. These are the same ones who get mad if the knife is sharp and they cut themselves. You just can’t fix stupid.

  3. Good article, Karen. Thanks.

    Far and away my favorite sharpening steel for kitchen knives is an antique with six flutes running the length of the steel. They create very sharp edges where they meet and those edges do a great job of sharpening an edge. I don’t know what kind of steel is in it, but it must be plenty hard as the sharpener is probably 100-130 years old and still going strong.

    If you want to see what I’m talking about, there is one on eBay at the moment. Plug in either eBay item number:401327136480
    or “Kitchen Equipment KNIFE SHARPENER & SKEWER- Reseller – MOP Handle & Steel”. I am not suggesting this is a good or bad example (but the mother of pearl handle is cracked), but it will do as an illustration.

    I tend to use mine about every other time I use the knife, so don’t have much of an issue with truly dull blades.

    Some people prefer pushing the edge of the knife into the steel or stone, as tho they were shaving pieces off, but I prefer to pull the spine toward me, alternating sides every stroke. Whatever people may claim is “the” right way, both work.

    One thing I finally figured out: Some knives come with lousy edges: They are ground to much too coarse an angle, which makes them far from optimally sharp.

    In that case you need to re-profile the edge on a coarse stone. I have a small paring knife which I could never get satisfactorily sharp until I realize that the edge angles were way too coarse. I re-profiled and it has worked fine ever since.

    For something like a machete or a shovel, I just use a flat file. No need to get fancy.

  4. Dave Larsen says:

    I dedicated my shop to tool sharpening. My deep secret to add is leather power stroping by wheel or I use a leather belt on a belt sander. You can keep a sharp knife sharp a long time using the leather power strop in between sharpening

  5. Karen,
    Very well written article. It’s basic, but I’m guessing that’s what you were going for. This is stuff I learned as a Boy Scout 4 decades ago. I used to blow my dad away with my ability to sharpen a knife while he still would destroy blades with power knife sharpeners.

    When you do your next article that describes the “Intermediate Level” of sharpening, let me suggest that you include “sharpening steels” and why they are used for deburring and not honing.

    Again, very well written.

  6. As JP said above

    I grew up hearing “more people are hurt with dull knives than sharp ones.” I have also learned that a cut from a sharp knife heals quicker.

    Amen & Amen. When I was about 14 or 15 years old I unfortunately had a dull knife with me in the woods cutting sassafras for tea. The knife stuck on a knot in the wood and I pushed hard to get through the knot. When it broke through the knot it flew forward and cut off the tip of my left index finger leaving a piece of the tip hanging by a thread. Two sutures at the E.R. held the tip on until it scabbed over and sloughed off. It all healed; but, the very tip of that finger still has no feeling in it.
    So dull knife + improper hand placement = a cut body part.
    The other thing with knives is that no matter the cost or style, is that they must be made from good quality steel, or they will not hold an edge, regardless of the sharpening tools and methods.
    I will use both dry and wet stones as well as a bench grinder if the task requires it; but, to keep all of our blades, from my EDC knives to our kitchen cutlery, I rely on some easy to use and inexpensive tools that anyone can use.
    This one has a tungsten carbide ‘V” notch in one side to rough sharpen, and a fine ceramic on the other side to do the fine hone. Either the DW or I will quite often do a quick pass on our kitchen cutlery before carving or cutting anything like a roast or a ham., to guarantee good slicing.
    Smith’s CCKS 2-Step Knife Sharpener

    This one also works well and helps keep our scissors sharp.
    Smith’s JIFF-S 10-Second Knife and Scissors Sharpener

    Remember, if you decide to try these out and get them from Amazon be sure to click MD’s affiliate link first to help him keep this site running.

  7. Smith sharpeners are great.

    OP, always thought Hollywood’s movies with samurai’s and ninja’s were funny. A sword takes a long time to sharpen and no self respecting samurai would hit edge to edge on a sword unless it was the difference between life and death. Lol

    • Thor 1,
      I agree on the samurai striking Katana against each other being very unproductive, since those swords were actually very brittle and could actually be caught and broken with a Sai or Jutte. I think the clashing of swords comes from the larger and a bit heavier broadsword.
      I recall a story (perhaps an anecdotal legend) from my early martial arts days about a samurai meeting some medieval knights.
      To impress the samurai, one of the knights demonstrated hacking an iron bar in half which took multiple hacks; but, did cut the bar in half.
      The samurai asked one of the ladies present for her silk scarf which he tossed into the air. He drew his katana from its sheath, made several very fast passes through the air in front of him and re-sheathed the blade as the now multiple pieces of the silk scarf slowly drifted to the ground.
      That is IMHO the definition of sharp.

  8. This is another good Smith’s sharpener. I keep one in my EDC bag, and others in our camp kitchen boxes here and on the Mainland. Very happy with them.

    Smith’s PP1 Pocket Pal Multifunction Sharpener, Grey https://www.amazon.com/dp/B000O8OTNC/ref=cm_sw_r_cp_tai_t51gzbW2WWVZA

    • Penrod,
      That sharpener looks pretty useful. It appears to work like the ones I have; but, with the addition of the diamond rod may be a tiny bit more versatile. The page you linked to lists it as a add on for $6.70 vs.$9.00 each in a two pack so it’s been added to my list.

      • Jesse Mathewson says:

        OP. I use the green, blue and red diamond sharpeners made by DMT with a small leather strop for go bags – and have a full set 60 grit through 8000 grit Japanese whet/water stones with multiple strops and varying levels of jewelers rouge for trailer/bol/home use- fits in a .50cal box

        Have at one point used and reviewed the smiths draw through setup, its okay if you do not have experience sharpening a knife… (not something to be ashamed of- its a skill not something easily learned) however, it is a skill I highly recommend especially if your someone who believes you have to have more of a knife than a morakniv companion for most bushcraft work 😉 (eg., beckerheads types are notorious for ruining their blades using “shuddering” machine sharpeners)

        Hand sharpening, save your temper-

        And learn from a true Japenese sushi chef…you wont find much better training in sharpening 😉 (unless you grow up doing it)

    • Greg Monger says:

      Penrod, thanks for posting that knife sharpener. I have an old version with a single sharpening groove for course sharpening, no ceramic groove and no diamond rod. I’ve been considering getting a new sharpener, looks like you came up with what I was looking for.

  9. Hi Greg, you’re welcome. I don’t use ours often, but when I do it gets the job done. No argument with Jesse about the usefulness of knowing how to sharpen a knife, but for an EDC bag or Get Home Bag this is very small, very light, and it works. I can refuse with that combination.

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