There are three ways to find out the angle at which a knife has been sharpened.
- Consult the manufacturer's documentation
- Use a laser goniometer available from CATRA at www.catra.org
- Use a marker to color in the bevel and follow the instructions below (recommended)
Here we'll outline the procedure using a marker. In the graphic below, we show a knife bevel with the edge and shoulder marked in fig. 1. Color in the entire bevel of the knife with a marker as shown in fig. 2; we prefer the Sharpie brand. Set a stone on the guide rod and lay it up against the knife, adjusting the collar until the stone appears to lay flat on the bevel. Make a pass or two with the stone and observe where the marker is removed along the bevel. If the marker is removed only from the bottom of the bevel on the shoulder as in fig. 4, then the angle is set too narrowly. Move the collar out a degree and try again. If the marker is removed only from the top of the bevel along the edge, the angle is set too widely. Move the collar in one degree and try again. When the stone removes all the marker in one pass, observe the angle indicated on the base rod at the inside of the collar. This is your angle per side. Your included angle will be the angle of each side added together.