Pop Ben Chapman‘s 3D printed knife sharpener onto the bottom of a standard coffee mug to use the unglazed portion of the vessel to hone sharpen a blade. Designed using Autocad 123D and printed on an Objet Connex 500 at his local TechShop, Ben’s sharpening guide angles a knife the correct 20 degrees necessary to produce a suitable edge.

Adam Flaherty

Adam Flaherty

I make cool stuff and write about other people making cool stuff on makezine.com. If you have something you think I should see, send me a tip.


  • tipaklong

    Ok this project is great! But it is mis-labeled. When you run your knife on the cup bottom, you hone it. Meaning, you realign the folded parts of the edge. Honing does not produce an edge, it brings it back. But there comes a time when honing cannot bring back the edge anymore, therefore you will then need to sharpen your knife. You sharpen either on a sharpening stone (oilstone or whetstone) with progressive grits from coarse to fine, sandpaper or grinding wheel.

    • Keith Neufeld

      If you were to run your knife along the cup top, you would indeed be honing it — straightening the edge that has become deformed during use. But the unglazed bottom of the mug has exposed abrasive, and running the knife along that is sharpening it. The Instructable links to an article detailing the technique of using the bottom of a mug to remove considerable material from a dull or improperly-sharpened knife to make it sharp.

    • Adam Flaherty

      Yep, you’re right and I’ve corrected the glaring mistake. Thanks for pointing it out.

  • LG

    An awkward Maker truth: FDM is s**t technology, and Photopolymer is awesome. This device (and many others) would be totally impossible to produce on a Makerbot style printer. We owe Adrian Bowyer a lot for the RepRap, but it is a technology that has had its day before it ever even cracked the mass market.
    Right now, buying a Makerbot is like buying stock in Buggy Whips *after* you’ve seen the Model T.

    • Keith Neufeld

      LG, that’s an interesting claim, since the Instructable shows this device being produced on a MakerBot Replicator. Only after prototyping did the author move to a higher-resolution printer.

    • Adam Flaherty

      RepRap is such an enabling technology. The road to innovation is littered with better technology. For instance, I was impressed when I saw the improvement with the Replicator’s new print heads. Then I saw a Ultimaker print. It was an order of magnitude better. FDM still has a way to go. I’d be more concerned if I were in the high-end 3D printer business.

    • http://twitter.com/unsped dr. unsped (@unsped)

      I have an Afinia H-series printer (US version of the UP) and the support structure feature for this series of printer is really quite good and you wouldn’t have a problem printing stuff like this. Photo-polymer is great also, except that it keeps shrinking as it cures, can have nastier msds, and the base material is crazy expensive, 1L = $100+ … so this sharpener would be like $50 … and not fit after a few days of curing. FDM with a loose fill and support structures your looking at a couple of dollars. Both techniques have there merits and detriments.

  • http://captivatingbore.wordpress.com captivatingbore

    Is there anyone else cringing as he drags the knife back and forth, rather than in one direction…or as he sharpens down toward his hand? Yikes!

    Neat idea, though! :)