Since making knives is a bit of a passion for me, it makes sense that I would also be interested in ways to efficiently sharpen them. Of course there is the traditional method of just using a stone and honing the blade by hand, but as satisfying as that is, it’s not very interesting. There are also several commercial jigs available that will ensure that you are sharpening at a consistent angle, but I had something else in mind: a knife sharpener that will hone both sides of the knife at the same time and maintain that perfect angle.
This is not my first attempt at making a knife sharpener. A few years ago I made this knife sharpener using the carbide teeth on an old saw blade.

To start, I made a test cut in my old oil stone. This stone had dropped on the floor a few years ago and broke in half. Even though I successfully glued it back together, it was still not very good because it had a couple of  chips missing:

I was surprised at how easy it was to cut. I used a diamond blade that is made for cutting tile in my table saw.
The basic idea here is to make two stones that interlock, like box joints. To do this, I made a series of very carefully spaced cuts in the stone, leaving “teeth” that were 1/8″ wide.

I cut all of the slots into the larger stone first, then cut that into two pieces. Luckily, they meshed together perfectly:

That was the hard part!

The easy part is making the rest of the jig, mostly from plywood, but I did use pieces of solid maple for the guide blocks:

And I used epoxy to glue the stones on. These guide blocks are cut at 10 degrees on the end where the stone is glued on, and that tilts the stones back at that angle.

The case was next and I made that from 1/2″ thick plywood. The sides were cut to provide an opening for the knife blade:

My original plan was for these stones to be 1-1/4″ tall and that would have left them slightly open at the top when they fully closed together:

But I messed up and cut them 1″ tall instead, and when they are fully closed there’s no space to start the knife at the top. So I added thin pieces of wood to act as stops:

Not a perfect solution, but better than nothing. And certainly easier than cutting new pieces of stone.

To spring load the stones, I used pieces of foam sponge cut to size:

There was some messing around to get the right amount of tension. In the end I settled on pieces that were about 1″ square that were compressed down to half that to pre-load the stones.

The last thing to do was to add the covers over both ends. I used screws for that only, and no glue. If the guide blocks ever jam or something else happens, I’ll be able to take it apart to fix it:

I made a video showing how I made it and also showing the knife sharpener in action:

And how well does it work? Great, actually. Even though this is a fairly difficult project to make, I highly recommend doing it if you want the absolute fastest way to tune up a knife. It’s especially handy in the kitchen.