Cylindrical Whetstone Knife Sharpener
thingiverse
You can buy these cylindrical whetstones for about £100. This seemed a bit absurd so I got a cheap stone and printed a holder for it. Including the whetstone and the bearings, this project cost me around £20 * The holder uses two bearings (22mm diameter, 7mm deep, 8mm hole) https://www.amazon.co.uk/dp/B07FDYTJS5 * And a 7.5cm diameter circular whetstone. I got one with a 180/320 grit surface. You could go higher. https://www.amazon.co.uk/gp/product/B08JC832K5 * 6x round neodymium magnets. 7mm diameter, 3mm thick. https://www.ebay.co.uk/itm/152103349104 Everything is a push fit. So the magnets should just push into the angle block. The bearings just push into the holes in the drum. You'll want to push the whetstone into the holder before attaching it to the drum as it might need some force to get it perfectly flat. You'll also probably want to measure the whetstone with some calipers before printing and adjust the size of the hole in the holder appropriately. (2 minute job in Tinkercad) Alternatively, you can always print out some shims or spacers. Some examples have been included. The magnet block has 15 and 25 degree angles. To use. Just soak the whetstone in a saucer of water for a couple of minutes before use (you don't need to remove it from the casing) and then clip your kitchen knife to the angle block using the magnets. It only takes a few gentle passes to sharpen the blade. Then flip it around and do the other side. Watch your fingers! It works surprisingly quickly and the knife can be very sharp.
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