Round knife sharpening jig version 3

3

The version 2 sharpening jig was okay but it was flawed in several ways. Some of the issues were due to lack of proper material/tools. The angle brackets were simply not ridgid enough to eliminate all unwanted movement. This could be fixed if I had access to welding equipment (and knew how to operate it) The size of the round knife blade itself also causes problems as it flexes if you press too hard while sharpening.

The universal joints are also a bit loose and the current 3d printed parts are also not without play.

All of these issues could be fixed but one thing that would be hard to change is the fact that the pivot point is not in the center of the blade. This causes the bevel angle to change from the points to the top of the knife. With the current design we a looking at something like 5 degrees which is quite a lot.

The need for a new jig came as I purchased a new round knife. The version 2 is not very suitable for different sizes of knifes and the new one simply did not fit.

Therefore I came up with a new idea which incorporates the best of the two previews versions.

Pros

• Knife blade securely held in place without the possibility for any unwanted movement
• Pivot point in center of blade
• small overall size

Cons:

• A bit cumbersome to shift grinding/honing from one side to another.
• only short strokes with the sandpaper is possible. 
• Each knife needs its own platform.

I was playing around with the dimensions while I was building it so everything is cut very rough. Also I have no propper workbench for woodworking and only very limited tools.

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Round knife sharpening jig version 2

5

I have made a sharpening jig for a round knife before as you can see here. The design was inspired by the apex edge pro. This time around I will base the sharpening jig around the wicked edge. Even though the first jig is able to put a decent edge on the round knife there are still too many "unknowns" The biggest problem as I see it is that you need to move the stone and the round knife at the same time. This will result in some unevenness in on the edge if you do not do it exactly the same each stroke.

With this new design you take out the movement of the round knife completely. The design is based on the wicked edge after seeing this video where Clay Allison sharpens a round knife. The wicked edge is not designed to deal with a knife like the round knife so he has to sharpen it in two sessions as he needs to reposition the knife. Being able to have the base of the swivel rod in the center line of the round knife will solve this problem. The repositioning of the knife is not that big of a deal and I could live with that.. The price on the wicked edge is however insane. As I have not been able to find a European deal I would have to buy it from he USA. The standard package is 299$ but that only goes to 600 grit. You would at a minimum need the pro pack I costing 425$. Adding to this is shipping, 25% in VAT + 12% customs + 23$ in customs fee. I dont know what the shipping is but the total without shipping comes in at a whopping 605,25$. I am not willing to spend that much on a sharpening system at this point.

For further inspiration as how to make the jig I watched these two videos Wicked Lansky and Lansky sharpening system modified...

They both use the lansky sharpening system as a base but uses universal joints and socket extensions bars to guide the sharpening stones. I almost bought the lansky system but came to the conclusion that the clamp would not hold the round knife very well. Also with the wicked edge system you really need two stones of each grit. Instead of the stones I will be using 3m micro finishing film and 3m lapping film using the "scary sharp" principle. The most informative site regarding sharpening that I have ever seen is this one:
http://www3.telus.net/BrentBeach/Sharpen/sitemap.html
Brent Beach really likes to sharpen plane irons using 3m paper with a simple but effective jig. Everything he says is well documented and often very controversial. The best quote from the site is this:

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Round knife sharpening jig

1

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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