15 May 2015

Round knife sharpening jig



The reason I did not buy a round knife earlier is the fact that they are difficult to sharpen. I have no experience sharpening normal knifes free hand so trying to sharpen a round knife would most likely not end well. When I sharpen knifes I use a sharpening jig. The one I use is a cheap clone of the Apex edge pro. I did however buy the original stones. This jig works very well.

Because of the round knifes shape it does not fit into the edge pro. I therefore had to come up with a solution making it either fit into the original jig or making something completely different. Initially my plan was to build a platform with a pivot in the center of the round knife. This platform should secure the knife and when rotated the edge would stay perpendicular with the sharpening stone. Having the stone perpendicular with the knife edge is the most common way of sharpening a knife. For some reason this is not the way most people sharpen a round knife. Doing it free hand you swipe the edge along the stone. Why you do this I do not know. Maybe because it makes it easier to maintain a constant angle or making sure that you sharpen the edge evenly.

After some simple mockups I decided to make the jig similar to the free hand sharpening.

List of materials:

Alu profile
Threaded rod M8
MDF 25mm
MDF 10mm
M8 80mm machine screw
3x M8 wing nut
2x M8 nut
2x M6 30mm screw
1x M6 wing nut
1x M6 nut
2x M6 60mm screw
2x M6 wing nut
5x 7x5mm magnets



The round knife when I got it.



It had some pretty deep scratches in it


I started with a dremel and a 538 drill bit


That removed almost all of the rust


I then used sand papir to clean up the rest.


Here is the base of the jig set up to a 15 degree angle. I used my phone a an angle meter app


Here the rotating piece has been taken of.



It can rotate 360 degrees but that is not required


This supports the alu profile


The alu profile with a stone held in place


To change the stones you just loosen the wing nut.






Here is a video of the jig in action




Close up of the blade



The result is pretty good. It cuts better than the utility knife I normally use. With some practice and a leather strop I think it can become even sharper. One thing is certain. If I had tried to sharpen it free hand the result would not have ben anywhere near as good.




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