Sharpness

[Bob Denman]

The one at 3:44 is great!!!

I think she was getting ready to shave his back...

 

[scdub]

I always read about folks getting a knife "hair popping sharp", implying this is the sharpest we can get a knife.

Welcome to BF!

Around here folks have come up with lots of ways to describe sharpness, but “hair popping” isn’t generally thought of as “sharpest”.

I think about sharpness “levels” like this, from least to most:

Dull
Working edge
Hair scraping (body hair)
“Shaving” (again - body hair)
Hair popping
Tree topping
Hair splitting/hair whittling
True shave sharp (beard)

I keep my straight razor at true shaving, a couple defensive knives at hair splitting, but mostly I’m happy with regular “shaving” sharp.

 

[ktataragasi]

https://imgur.com/NMzYuKE

 

[YaArArYa]

Its sharp for me if it cuts News Print.

 

[bdmicarta]

I am 58 years old. Been using a whetstone since I was 5 or 6 years old. Won't say I was using it correctly at that age, but everybody has to start somewhere.

Anyway, to the point. I always read about folks getting a knife "hair popping sharp", implying this is the sharpest we can get a knife.
I don't think this is correct. I like it better when the hair just gets cut and lays back on the blade, implying a cleanly severed hair, no stress as it is cut, it just lays down, kinda like a sharp sickle bar does with hay.

Change my mind......

You know how people are- there are always people somewhere that take things to an extreme. I don't think anyone knows what the sharpest is that we can get a knife. Today people use a progression of very fine stones to get edges that don't just "pop" or "sever" hairs, they can start carving little slivers off of the hairs. Nevertheless I'm sure that someday they will figure out how to go beyond this.

A sharp knife is a safe knife.

I've heard that before, and I understand the concept, but it doesn't apply to knife enthusiasts. I'm not the best sharpener in the world but I can sharpen a knife far beyond this point. The concept of the old saying is that if you have to put a lot of force into a cut you can slip and cut yourself, if the knife cuts and you don't push as hard then you won't injure yourself. But with something sharpened by an enthusiast, any little slip and you can get a serious cut, so you don't treat that as a safe knife, you treat it with maximum respect.

 

[CarolinaJack]

http://knifegrinders.com.au/Manuals/Sharpness_Chart.pdf

"Hair popping - the hair bends before it cuts, and the severed hair part will “jump away”. Requires at least 30 BESS or 0.05 micron edge. I couldn’t make a hair pop with the 35 and 40 BESS edge."

"Silent slicer - at 20 BESS and under the hair falls effortlessly as soon as it touches the edge; not jumping away like with popping, just silently falls, indicative of a 0.01-0.03 micron edge."

Thank you for this. Exactly what I was looking for!