Confused about exact sharpening angles?

In a recent discussion on proper sharpening angles and use of the KME system, one of our most experienced friends questioned ...

"Just now I touched up my 6 Tuffheads for the hunt, using my KME knife sharpener. According to the scale on the sharpener it was set at 25 degrees. But in order to get the stone to lie precisely parallel to the bevel on the heads I had to raise it up to one mark below 30 degrees – 28 or 29 I reckon. So is the scale off on the jig, or the bevel in fact greater than 25 degrees, or something else I’m missing here? Just curious. In any event those heads are sharp and one has already drawn blood, my own."

A quick response from Rom Schwartz at KME explins the details...

"Figured I'd share this drawing to help explain why Dave needs to set the shapener to 29 degrees in order to match a 25 degree bevel.

The angle scales on all clamp-on sharpening systems are relative, not absolute. This is because there are multiple factors that influence the actual sharpening angle.

We can adjust the angle by raising/lowering the bearing guide but the distance the blade extends out in front of the clamp has just as great an influence on the angle too.
This is just basic geometry and there's no escaping it.

The best way to match an existing bevel is to color the bevel with a permanent marker, eyeball the angle as best as we can, then take just a few strokes with a dry stone to see where the ink is being removed. If the ink is being taken from the shoulder of the bevel but not from the cutting edge, that means the angle is set too low. If we're removing ink from the cutting edge but not from the shoulder, that means the angle is set too high. Micro adjust till the ink is being removed from the whole bevel and you have found the correct setting for that particular knife or BHD. Note: it's preferable to have the angle set a bit too high than it is to have it set a bit too low. This way we're certain that the stone is contacting the actual cutting edge.

Dave when sharpening Grizzly El Grandes with the knife sharpener, I find that I need to set the sharpener at 27 degrees even though I know that the factory bevel is ground at 25 degrees. The angle scale may indicate that I'm sharpening the Grizz at 27 degrees but in fact it's actually sharpening at the same 25 as my original "factory" grind. 


Sorry for the poor quality of the sketch but I think you'll see what I'm talking about.  Thanks,   Ron

Ron Swartz

KME Sharpeners


Ready to Order? -  Call 217-345-8600 or Order Online

Order Online Now!
       Made in the USA      bevel-sharp