Measuring grind angle

[Maelstrom78]

Almost positive that this is a dumb question, but nothing ask nothing gained. How do you measure the angle of a grind? I think its this link that had me confused.
http://www.knifeforums.com/forums/fbbuploads/1167340105-asym_angles.jpg

I was looking at it to see the head on view of a 70 / 30 grind. But I'm not positive I can tell how they are measuring the different angles. Plus I'm not sure this is how typically angle is discussed in knife making parlance. Can anybody shed light on this? Thanks!

 

[12345678910]

http://www.wixey.com/anglegauge/

set your platen with this or that

 

[MarkJeffrey]

I had never even heard of those 70/30 and other grinds until the thread that link was in, I just read that today. It looks like the angles are measured from the 90* centerline.. and the 70/30 80/20 is the percentage of the 'pie' on that side of center? I'm just guessing.. somebody that actually knows will be along shortly

 

[P.Brewster]

I think the convention used for drill bits is pretty straightforward and used by many:
"Point angle" (drill) or "grind angle" (knives) = angle between centerline and one bevel face
"Included angle" = angle between one bevel face and another bevel face


70/30 etc seems to be a convention used for kitchen knives. The best summary I could find is "70/30 just means that 70% of the bevel is on one side of the line and 30% is on the other. . . Now note that depending on the other dimensions of the blade, each side could have the same angle, or each a different one. But angle isn't really related to ratio." http://www.cheftalk.com/t/63443/bevels-double-bevels-angles-im-confused

 

[Matthew Lomas]

Trigonometry.