Someone asked me how the laser protractor works…it is really simple. The protractor fires a perfectly straight laser beam that strikes 0 degrees on the scale when no knife is inserted. When a knife edge is inserted in both back and front v-slots and the laser is triggered, the shiny edges of the edge bevel each reflect that beam at the angle at which it has been ground (the angle of reflection will equal the angle of incidence). A 20 degree bevel will reflect to the 20 degree scale (from both sides). If the beveled edges are not the same the difference will be shown on the protractors scale…e.g. 20 degrees/ 19 degrees on the protractor’s scale.This neat device works best in slightly subdued light in order to prevent false readings caused by bright ambient light also bouncing off the shiny edge.
If the knife is canted all th way to one side in the v-slots, lying flat on the sames sides back and front, when the laser is fired it will read you the sum of the two edge bevels on the protractor’s scale. It is simplicity itself and a wonderful help when you don’t know the edge angle on an unknown knife or to confirm the angles you have just developed.
I hope this helps to understand the basic use of the laser goniometer/protractor.
Leo
