Measuring angle of the edge

[Stacy E. Apelt - Bladesmith]

Take a small folding knife blade, that measures 3/8th high by 3/32 thick at the spine ; a blade with this geometry can sport a bevel grind that measures 2 degrees per side. This blade can be sharpened using an angle of 3 degrees or 6 degrees inclusive at the edge measured from the center line. This grind makes for one scary sharp folder blade

Yes, but regardless of how thin the blade is and how low the bevel angle is, the edge angle will not survive on a folder at 6° inclusive.

I make sashimi blades with bevels that are around 2-3° inclusive. While that makes a super thin slicer, the edge angle is still sharpened around 10-15° inclusive. If it was more acute, it would be too fragile. I doubt you could tell the difference in the first few cuts between a 6° blade and a 15° blade, but after fifty cuts, the 6° blade might appear dull, while the 15° blade will still be scary sharp. There is such a thing as too sharp.

 

[Fred.Rowe]

Yes, but regardless of how thin the blade is and how low the bevel angle is, the edge angle will not survive on a folder at 6° inclusive.

I make sashimi blades with bevels that are around 2-3° inclusive. While that makes a super thin slicer, the edge angle is still sharpened around 10-15° inclusive. If it was more acute, it would be too fragile. I doubt you could tell the difference in the first few cuts between a 6° blade and a 15° blade, but after fifty cuts, the 6° blade might appear dull, while the 15° blade will still be scary sharp. There is such a thing as too sharp.

I believe you are correct; a blade with a very acute bevel angle will hold up at the edge longer with a less acute secondary grind at the edge. The angle selection itself depends on the intended use. There are fewer uses for a 6 degree edge on a 2 to 4 degree bevel than there are for a 15 degree inclusive edge on the same knife; this assumes the bevels were taken to a zero edge before sharpening. Thickness at the edge before the secondary edge angle is applied is a must consideration also.
It would make for an interesting study too, if the different grinds could be closely photographed so you could see the changes in the edge under magnification. Do you know of a study like this?
I like to try different grinds at the edge.

Fred