Frequently Asked Questions

  1. Where can I buy your sharpeners?

    DMT® products are available nationwide through most hardware chains (Ace, True Value, Do It Best, Sears), professional tool distributors, camp/sport stores, wood & craft stores, and culinary/gourmet stores.

    Click on the link below for a list of retailers, including telephone numbers and web site links where DMT® products can be sourced. Find a Dealer

    Or go to our newest outlet:

    The DMT® Online Store

    If you need further assistance, contact our Customer Service Department toll free at 800-666-4368, ext. 1 or contact us using our Customer Service Email Form.

  2. Which grit should I use?

    Which grit you should use depends: How often do you sharpen? How dull do you let your knife or tool edge get before you re-sharpen it? How sharp is sharp enough for you?
    Ask yourself these questions, and then read the grit descriptions below to determine which grit(s) best suits your needs. Hint: the pros use more than one grit & move from coarser to finer grits as they sharpen. Therefore our top recommendation is for you to consider one of our two-grits-in-one-tool models (Double-sided Diafold® Diamond Whetstones™ or DuoSharp® Diamond bench stone models).

    If you’re still not sure, call Customer Service at 800-666-4368 ext. 1. Our office is open Monday – Friday, 8:00 a.m. to 5:00 p.m. EST.

    Extra Extra Coarse- Use when excessive stock removal is needed, this will do the job quickly and precisely. DMT®‘s bench stone has a surface flatness to +/- 0.001”, is perfect for flattening water stones, Arkansas stones and synthetic stones. Also, a safe alternative to powered grinding with no worries of heat build up that can damage tool temper. Color code: Silver. Size: 120 micron / 120 mesh.

    Extra Coarse- Recommended for aggressive removal of metal on damaged tools or for heavy-duty outdoor tools such as axes and lawn mower blades. This grit is great for flattening Japanese waterstones and is also commonly used as the first step in flattening the backs of chisels and plane irons and for rapid stock removal from a chipped or badly damaged edge. Color code: extra coarse (60 micron, 220 mesh) “black”.

    Coarse- Quickly restores a dull edge to cutting sharp again. Customers that desire cutting fast action without worry of edge refinement often use our coarse models. Color code: coarse (45 micron, 325 mesh) “blue”.

    Fine- Restores to a fine edge any knife or tool that is slightly dull. Many of our customers consider the fine grit to be a medium/all purpose sharpener. Professional Chefs and gourmet cooks prefer using our fine grit models. For woodworkers and sportsman who are stepping through the grits, it’s the edge refinement step done before micro beveling and polishing. Color code: fine (25 micron, 600 mesh) “red”.

    Extra Fine- Refines and polishes the sharp edge to razor sharp perfection. If you are new to sharpening or if you do not need your knife or tool edge to be as sharp as absolutely possible, this grit is not recommended. But if it’s not sharp until it’s sharp enough for you, this is the grit you are looking for! Color code: extra fine (9 micron, 1200 mesh) models “green”.
    Ceramic- Polishes edge to a mirror finish. Color code: gray.
    Grit Size: 7 micron / 2200 mesh

    Extra Extra Fine- Provides the finest grade micronized bonded diamond abrasive available anywhere for the ultimate edge refinement down to a polished edge. Quick stock removal with millions of diamond cutting edges. Color code: tan. Diamond size: 3 micron (or 8000 mesh).
    View Color-coded Grit chart

  3. I’m interested in buying your products. Could you please send me a price list?

    We are happy to send you a Full Line Catalog, Sharpening Guide  and/or price sheet.  You can go to our "CONTACT US" tab and click on "Contact Us" and submit the form asking for whatever material  you need or call us toll free at 800-666-4368.    Or you can download a full line catalog,  sharpening guide and price sheet by going to our "RESOURCE" tab, and click on "Catalog and Brochures", open and save to your computer these pdf files.

  4. What is the warranty on your sharpeners?

    The DMT® Commitment:
    For more than thirty years, DMT® has been committed to innovate and produce the world’s finest diamond knife and tool sharpeners. All DMT® products are made using the highest quality materials and workmanship and are guaranteed to be free of defects. Any product found to be defective, will be replaced free of charge – it’s that simple!

  5. How long should the Diamond last on a sharpener?

    It depends on how often you use it, if you use it properly, and if you keep it clean and properly stored. When used properly, kept clean and stored dry, DMT® diamond sharpeners will last a very long time. They do not last forever, but they last for years and years. If you use your sharpener as part of your daily work and use it many times a day, you will likely need to replace it in a few years after extraordinary service. If you use your sharpener to sharpen your kitchen knives every so often, chances are your sharpener will last ten or more years. Some of our customers report their DMT® sharpeners are still performing after twenty years of service!

  6. My sharpener doesn’t seem to be flat enough, how flat should the sharpener be?

    DMT® sharpeners are very, very flat. The DuoSharp® models are engineered to be precision flat – incomparable to any other sharpening stone on the market today. However, if you are concerned that your sharpener is not flat enough for your application, send it back to us for evaluation. Please send it to
    DMT® Customer Service
    85 Hayes Memorial Drive
    Marlborough, MA 01752

  7. How do I take care of my sharpener?

    When you first use your DMT® sharpener, the diamond surface will seem aggressive in nature; the diamond sharpener will smooth after initial sharpening with no impact to long term performance.  Your first few sharpenings are the break-in period.   To maintain your sharpener, you should clean after each use with water and wipe dry. After several sharpenings, use a mild kitchen abrasive cleanser and a nylon scrub brush (an old toothbrush works well too). Comet, Ajax, and Zud work well. Make sure the sharpener is dry before putting it away.

    Storing your DMT stone:  Always put away dry and store in a dry area.  Use leafing (paper towels, cloth, plastic storage bag) in between your bench stones to prevent abrasive sides from rubbing.    Use and Care.      Cleaning DMT Diamond Stones Video.

  8. What are the seven settings on the Aligner™ Guide?

    The exact angle on the Aligner™ Guide will depend on the knife you are using with it. Based on a 1” blade, the settings range from 20 degrees (shallowest) to 40 degrees (steepest). The seven choices are: 16, 20, 24, 28, 32, 36, and 40 degrees. As you extend the guide rods out on the knife clamp, the angle of your knife becomes steeper relative to the diamond sharpener.


     Angle Chart

  9. I think my sharpener may have worn out, what do I do?

    First, clean it. If you have not cleaned your sharpener on a regular basis, it could be full of metal fines (swarf buildup) which is clogging the stone surface and affecting its performance. If you are concerned that the diamond may have worn off the stone, rub the sharpener against an old glass jar. If the sharpener scratches or frosts the glass, then there is diamond on the sharpener ready for your sharpening needs.      Use and Care.          Cleaning DMT Diamond Stone Video.

  10. I know it says to use the sharpener dry or with water, but can I use oil anyway? Can I store my DMT stone in kerosene?

    DMT recommends you use DMT products dry or with water only. Although mineral oil or WD40 will not harm the DMT products, they can impede sharpening if used in excess and can damage the sharpener overtime if not properly cleaned/removed from the sharpener. DMT recommends that you always wipe your Diamond and Unbreakable Ceramic Sharpeners clean and store dry after use. 

    Put away your benchstones dry and store in a dry area.  Use leafing (paper towels, cloth, plastic storage bag) in between your bench stones to prevent abrasive sides from rubbing.

  11. I have a DMT® sharpener and I can’t seem to get my knife sharp. What am I doing wrong?

    Chances are you are not maintaining a constant angle. We recommend sharpening at a 20-degree angle. That means positioning the knife so it is resting on the sharpener at about 20 degrees. If you are not sure what 20 degrees looks like, you could put two quarters on the sharpener and rest the knife on it. That will be very close. However, sharpening at the proper angle is not as important as sharpening at a constant angle. 

    In order to sharpen properly you need to maintain a constant angle. Lock your wrist. If your wrist wobbles and therefore does not keep the knife at a constant angle, you will not be able to sharpen you knife. If you are new to sharpening and you’re not sure if you are holding the knife at a proper angle or not, we recommend the following:

    Use a black marker and draw a line on the bevel of the knife. The bevel is the shiny part at the edge of the blade that has a different angle to it (that’s that part that does the cutting). After you have drawn a line on the knife bevel, sharpen it. Look at the knife to see if all the black is gone. If it isn’t you can see whether you need to raise or lower the knife angle during sharpening (by raising or lowering your locked wrist).

    If you need further assistance, call Customer Service toll free at 800-666-4368 ext. 1. Our office is open Monday – Friday, 8:00 a.m. to 5:00 p.m. EST.

  12. Can I sharpen figure skates or hockey skates with a DMT® sharpener?

    We do not recommend sharpening figure skates with a DMT® sharpener. The bottom of hockey skates should also be sharpened professionally because there is a hollow grind on the bottom of the blade. DMT® sharpeners are great for taking the burr off the side of skates. In fact, many professional hockey players use DMT® sharpeners during practice and during games to remove the burr off their skates – just like skiers and snowboarders do.

  13. How do I sharpen my speed skates?

    DMT® had been a sponsor and supplier of Diamond Sharpeners to the Olympic US Speedskating and USA Luge teams. Many professional speed skaters use the DMT® 250mm DuoSharp® to sharpen their speed skates. They put the skates in a specially designed clamp holder so the blade is pointing up. More than one DMT® grit is used to get speedskates medal-winning sharp. The most popular grit combinations for speedskates are coarse/fine and fine/extra fine. Some skaters use the extra coarse/coarse stone and progress to the fine/extra fine stone. Holding the sharpener flat (at a right angle) against the blade bottom, one moves the sharpener across the blade from toe to heel back and forth a few times. Then move to the next grit repeating the same stroke. Always start with the coarsest stone and end with the finest.

  14. Do you have sharpeners that will work on my sword collection?

    Yes! Many of our sharpeners can be used to sharpen swords. The most common models are either a DMT® Diafold® Diamond Whetstone™ sharpener or a 6” Diamond Whetstone™ bench model.

  15. My DuoSharp® bench stone has holes on one side; what are these?

    The holes are there intentionally, a by-product of the manufacturing process and in no way affects the peformance of the bench stone.

  16. What is the advantage of using the Burr Doctor®?

    The Burr Doctor® is perfect for quick deburring of nicked edges caused by ice or rocks and can be carried in a backpack or pocket. It is adjustable to fit your beveled ski/snowboard edge.
    The Burr Doctor™ has a 0 – 5.5-degree adjustability. The stone is smaller (about 1.5” x 1”) and can be purchased separately when the original stone is lost or worn. Small enough to carry in your pocket, the Burr Doctor™ is perfect for quick touch ups and on-the-spot treatment of burrs.

  17. Which grit is the best grit to use to flatten my Japanese water stones?

    DMT has engineered a product designed specifically for this purpose; the DMT Dia-Flat® Lapping Plate. It utilizes 120 micron / 120 Mesh size diamond to quickly flatten any grade of waterstone or any other type of sharpening stone. Use of our newly developed proprietary DMT® Diamond Hardcoat Technology™ allows the Dia-Flat® to withstand the extreme service conditions incurred when flattening other abrasive sharpening stones. Ideally, use under running water or submersed in a pan of water for best results in order to quickly flush away the slurry that is generated when flattening. (Note: do not use in a sink that has a garbage disposal unit as the slurry is detrimental to the disposal bearings)   Always clean/dry your DMT Dia-Flat® after each use as build up of material on the stone from flattening may be significant.  Refer to care and use of DMT stones Q&A #7.

    Some DMT Diamond Sharpeners could be used (and have been used) for flattening, however, they were designed for sharpening, not flattening, therefore, DMT assumes no liability for sharpening stones worn out due to this method of use.  DiaFlat Video

  18. Why can’t I buy directly from you?

    As a manufacturer, we sell to retailers and distributors. We rely on specialty retailers worldwide to sell our products, help educate the public on the importance of sharpening, how to use DMT® products and to assist in product selection. For those who wish to use the internet for their purchase, view our website for a selection of vendors including a dealer working as our “online store.”. If you have difficulty locating our products in your area, please contact Customer Service toll free at 800-666-4368 ext. 1 for assistance. Our office is open Monday – Friday, 8:00 a.m. to 5:00 p.m. Eastern Time.

  19. Why is there “smoke” when I first use my ceramic sharpener?

    Break in of Unbreakable Ceramic Surfaced Product
    DMT‘s unbreakable ceramic sharpener is produced using a patented process called Micro Arc Oxidation. This process is used to transform the surface of aluminum into an unbreakable, wear resistant ceramic (Aluminum Oxide) abrasive.

    The Process

    The oxide layer literally grows inward into the Aluminum by approximately 75% and outward by about 25%. Coating thicknesses can vary between 30 and 150 microns (or approximately 0.001” to 0.005”) depending on how the coating process is carried out. The process produces a two layer coating of ceramic; the outer layer (Gamma) being somewhat granular and chalky and the inner layer (Alpha) a very dense and hard ceramic abrasive.

    How This Affects My Sharpener
    Sometimes some of the Gamma phase layer remains on the product’s surface until the sharpener is used. It is not unusual to see traces of this outer granular Gamma phase layer slough off during your first few sharpening strokes. It looks like smoke. Do not be concerned by this. It is to be expected and considered normal due to the two layer base structure of the ceramic. After the first few sharpenings, this outer layer will be completely removed, leaving you a very hard, long wearing unbreakable ceramic sharpener which will provide the ultimate in edge refinement.

    Use gentle and smooth stroking to ensure long life of this product.  Excessive force and hacking will result in damage and void warranty.

    When cleaning is need, the ceramic surface can be cleaned using a high polymer eraser. 

  20. Do you have anything that I could use to sharpen my bread knife or serrations on a folding knife?

    Yes! DMT® has a Diafold® Serrated Knife Sharpener in a tapered cone shape which is perfect for sharpening the wide serrations on a bread knife, the smaller serrations on a pocket or folding knife and anything in between. Since the rod is tapered, a variety of sizes of serrations can easily be sharpened using DMT®’s Diafold® Serrated Knife Sharpener. For extra large bread knife serrations, try using our Diamond Steel™.          Serrated Knife Sharpener Video.

  21. What is the difference between DMT’s traditional “polka dot” Diamond Whetstone™ sharpeners, the continuous diamond surfaced Dia-Sharp® line and the unbreakable ceramic sharpener?

    It is important to note that all DMT diamond products are manufactured to the same high standard using the same high-quality monocrystalline diamond that makes sharpening with DMT products consistently reliable and superior.  Therefore the difference between the two diamond product lines becomes a matter of preference to the user.

    The unbreakable ceramic sharpener is a finer grit than most of our diamond products and are the next step to achieving a polished edge.

    The Diamond Whetstone™ and DuoSharp® lines:

    These products carry our signature polka dot pattern surfaces.  The polka dots are slightly recessed so that when you are sharpening the small amount of material (swarf) that is being removed will fall into the polka dots and remain out of the way of the sharpening surface, making your sharpening work quick and easy.

    The DiaSharp® line:

    These products have a continuous diamond surface, which makes them perfect for small-pointed tools as well as your other sharpening needs. They are constructed of solid steel, which makes them heavier than our engineered-resin Diamond Whetstone™ and DuoSharp® lines.

    When compared with conventional sharpening stones, all DMT products work faster and sharpen quickly using light pressure and rest assured that your DMT stone remains flat!