Laser protractor

[Mr. Swede]

Howdy.
I wonder if it's possible to get the edge angel on a serrated knife with a laser protractor?

 

[Twindog]

You get two long red lines covering a lot of angles. I don't know how significant it is because the reflected laser line is showing you a wide range of angles collected from all the curved surfaces of the scallops.

The thing to remember is the laser angle represents the angle of the beam that is reflected off the edge at one specific spot -- but there are a lot of spots. The beam cannot ignore anything on the edge. It reflects everything.
Even grinding lines get reflected.

The scallops are something like a convex edge. A convex edge has no angle, contrary to popular opinion. It has a range of angularity. Near the apex, the laser will reflect off a specific point and give you an angle, but the angle is only for that one spot. Move up the edge, and the angularity will decrease; the reflection off a specific spot will show you an angle for that specific spot that is more acute than the spot below it.

So what you get is a crescent line showing the range of angles from the lowest to the highest. There is no angle, but you can get a representation of the angularity of the whole convex edge.

With a scalloped edge, you have a lot of reflections from all the various curved surfaces on the edge; and I don't know how you'd sort them out.

 

[Mr. Swede]

I see, is there another, fairly easy, way to determine the angle. My project requires I get the angle in numbers.

 

[Twindog]

I see, is there another, fairly easy, way to determine the angle. My project requires I get the angle in numbers.

Use a stone -- either a round stone the same diameter as the the scallops or a sharp-angled stone, such as the Sharpmaker stones -- and paint the scallops with a Sharpie. Then measure the angle at which the stone cleanly scrapes off the ink for the whole breadth of the scallop.