Compensating for a knife's primary grind angle with the edge pro

[Luckylefty01]

I recently purchased an edge pro, and one of the things I immediately noticed is that setting the sharpening angle by using an angle cube with the stone set on the edge of the bed does not take into account the angle of the primary grind on some knives (including most of the ones I'll be sharpening). To sharpen at a specific true angle you need to set the EP angle to the sum of the angle you want and the angle of the knife's primary grind.

I'm not the first person to notice this, and I've found recommendations for doing things like setting the angle by sharpening with the blade's riccaso on the EP table, but I came up with a solution that seems simpler. I wanted to run it by you guys to see if there's anything I was missing.

What I've been doing to determine the primary grind angle is to zero my edge cube on a flat surface, place the primary grid of the knife on the surface the same way I'd place it on the EP bed and then measure the angle of the primary grind on the opposite side with the edge cube. This is the angle of both primary grinds together, so to get the angle of a single primary grind I divide by two. I then add that number to the angle I want to sharpen at and set the EP accordingly using the edge cube.

Example:
Using the method above for my BM 705 the angle shown on the edge cube is 9.7º, so each primary grind is 4.85º. To sharpen the edge at a true 15º angle the EP must be set to 15º + 4.85º = 19.85º.

 

[mrdeus]

Sounds about right.

I do it in a similar way. I put the knife with the ricasso (if it has one) flat on the edge pro. I put the angle cube on the blade and zero it, then I lay the blade flat on the grind on the EP and add that angle to the edge pro arm.

I've also heard some people sharpen just a little section with the ricasso on the EP table, then colour it with a marker, lay the blade flat and adjust the angle until the marker is removed cleanly with one stroke with the stone.