Most home knife sharpeners have you drag the blade across a sharp edge or small diameter grinding surface. While this works well initially, after repeated use, it'll start to form divots on the edge -- kind of like washboarding on a dirt road -- eventually turning your knife edge into a ragged mess. This rolling sharpener works more like a sharpening stone, where the flat surface keeps the edge flat and even.

Just like those pricey rolling diamond sharpeners, this one uses a 3"/76mm dia. 2-sided diamond grit stone. (Sharpal 216N, ~$20). One side is very coarse (220 grit) for roughing in your bevel, and the other side is 600 grit that can be used for your final edge and for honing. The diamond coated steel disk is held in place with three 12mm dia. x 3mm thick neodymium magnets. There is a thumbnail cutout in the edge for prying the diamond stone out to flip it over.

Also check out my earlier Rolling Knife Sharpener that uses emery or aluminum oxide sand paper instead of a sharpening stone.

The knife holder holds the blade at a fixed angle with three more 12mm dia. x 3mm thick neodymium magnets. Sitting flat, it holds the blade at 15 degrees, but there is also an adjustment screw that will raise the angle by 2 degrees per rotation of the screw. Once you've got it set to the proper angle, roll the sharpener back & forth along the blade with light pressure, as shown in the animation. Just make sure that you are pressing the front edge of the holder firmly against your worksurface so that you are getting 3-point support from the front edge of the holder and the adjustable post in the back.

Assembly of the sharpener is simple: just screw the two rotating discs together through the center of the cylindrical body. The 6 magnets are held in place in the pockets on the sharpener and holder with a drop of superglue. I added wide rubber bands as tires to the crowned edge of the rollers for a smoother feel, but it'll also work without them. For the knife holder, you just need to superglue the three 12mm x 3mm magnets in place and then insert the angle adjuster screw. Oh, and if your plastic wants to squeak, just use a little light grease or oil on the shaft during assembly.

Items needed:

Six - 12mm dia. x 3mm thick neodymium magnets

One - Sharpal 216N diamond sharpening stone