I made these jigs to set the angles on my grinder platform. They have a flat edge that sits on the platform, and two points to register on the grinder wheel.
Making them is pretty straightforward. Below shows the geometry layout. I drew it on paper as illustration, but for the jigs I made, I actually drew the geometry directly on a the wood and cut it out.
I start with a 8″ diameter (4″ radius) to represent the grinder wheel. A straight line through its center marks “level”. Measure the desired angle (40 deg in this picture) from this line at the point where it meets the circle – this is the flat bit that rests on the platform. Next, you want 2 points to rest on the wheel (these are circled in the above picture). These two points and the flat for the platform are the only important bits. The rest can be cut however you like. I like a big hole for my thumb to hold the jig on the platform. It is also useful for hanging the up jigs (on some pegs I’ve attached to the leg of my grinder stand).
The picture below shows the cutout jig sitting on the drawing, so you can see how matches.