Cylindrical Whetstone Knife Sharpener

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 minut