Sharpening training wheels. Knife sharpening tool - compact fixed angle system for any stone

Combines the benefits of free-hand sharpening and a fixed-angle system. It takes less space than a full fixed-angle system, allows you to use any stone, and is quicker to use. Just put a knife on a magnet, set the angle with a screw, and start sharpening.

It's also less printing than other sharpening systems I found. It takes ~45-50g of filament and about 3-4 hours to print.

If you want to learn how to sharpen knives on wetstones or diamond plates, but have trouble maintaining the angle, this device will help you. It's like training wheels for knife sharpening.

The first version used a steel M5 or M6 threaded rod (or long screw) and nuts. v2 is fully printed - you only need magnets.

Assembly

1. Press a magnet in each hole. It is a tight fit - using a vice or a carpenter clamp is the best method.

2. Slide the knife support part, then put the short flat screw in, and screw on the smaller nut.

3. Screw in the slider rod, and put the bigger nut on top. You can add a rubber o-ring between the nut and the main body - it will stop the nut from moving when adjusting the angle.

Threads will be tight at first, but they will loosen after a few turns.

Magnets are not equal in strength. I have 10x2mm magnets that are strong enough, and some 10x4mm that are weaker, so I need to place two of them in the front sockets to make the connection more secure. The back side of the sockets is looser, so you can add more magnets without pressing them in.
With weaker magnets, the device is still useful, but it requires more attention - it will help you maintain the angle, but won't hold it by itself. It could be a 'learning mode' for completely freehand sharpening.

How to use

Place a knife on the magnets and adjust the support so the edge of the knife sticks out by a few millimeters, and the knife is held firmly. Put the knife on the sharpening stone at the desired angle, and set the slider screw so the rounded end touches the table surface. Secure with a nut. Move the knife across the stone, making sure that the slider is in constant contact with the table. Sharpen one side until you can feel a burr along the upper side of the edge. Flip the knife on the device and repeat the process. Next, start making light paces, moving only forward to the edge and changing sides after each pass. Then you can go to a finer grit or a strop.

If you use stones of different heights, make sure to adjust the angle (by twisting the longer screw) or just put something under the smaller stone to level it. You have a 3D printer, you can probably make some wetstone adapter base ;)

How to set the angle

There are various methods of getting the angle right:

1. Use an angle indicator (like this), put a knife on it, make sure the edge is touching a stone, and twist the screw until it touches the table.

2. Use a bubble level app - place your phone on top of the device to check the angle.

3. Eyeball it ;) The exact angle is not as important as making sure it is consistent.

4. Sharpie. If your knife was previously sharpened at the correct angle, take a sharpie and colour a bevel. Make some light passes and check where the colour is removed.
     - only on edge - lower the angle.
     - only behind the bevel - increase the angle.
     - whole bevel surface - perfect.
   This method is useful if you are progressing to the next stone with a different height.

For 1 and 2, with thick blades, take into account that the real angle will be altered by the angle of the knife's primary grind.