How does one shave to test sharpness?

H

HighTen

Joined
Aug 28, 2004
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I realized that I don't know how to do this. I have a few knives sitting around and I want to know how sharp I'm getting them. I've read a lot about people shaving a little hair from their arm or something. How is this done? What kind of angle to you hold the knife at and these kinds of details...
Thanks. :)
 
for me I just more or less scrape the blade edge first along my arm (often trying two different parts of the blade, to make sure both the back part and the tip are sharp), I think at more of less the angle you'd use for stropping/sharpening, and if hair comes off, you're good. You're welcome to try varying the angles and such to find one that works best (I wouldn't try perpendicular to the arm, though;))
 
The closer the flat of the blade is to the arm, the better. :) Raise the back very slightly and scrape gently, because a really sharp edge will take the hair off effortlessly, which means is will slide into flesh just as quickly.
 
Hey Esav

You're really right about the angle thing. I was going lightly at about a 45 degree angle and not getting really good results and this was after a decent session with the Edge Pro set at the 18 degree angle. I used the angle with the spine of the knife barely raised and the hair flew in all directions. :cool:
 
My brother didn't think my CRK Shadow IV could take any hair off due to it's blade size (thick) he soon had a 1" patch of nothing on his arm! :thumbup:
 
If you want a real measure of sharpness, try shaving the stubble on your chin. Compared to that, arm hair is child's play. :D
 
Arm hair is pretty delicate, and shaves real nice. Like sodak indicated, chin hair is alot tougher stuff (assuming you''ve been shaving for a few years). But for a real "ballsy" test, take a swatch of pube hair!
 
IMHO this is a silly test.

It is right up there with paper cutting.

A knife is not a razor and will be used differently than a razor.

I could sharpen an edge on a butter knife that you could shave hair with. This is a rather simple task. You just need a very narrow blade angle.

I don't know what this proves except that I can hold a very consistent narrow angle when sharpening. However the knife will not hold the edge very long. It will dull quickly although it can shave hair off my arm or slit paper. My Gillette razor can do this even better!

What I would be more interested in knowing is how many deer will the knife gut, skin, and quarter before requiring sharpening? Or how many times can I cut the lines on my boat before the knife needis sharpening? Or how many branches can I trim in the garden, etc. etc.

If you can put a 40 degree edge on the blade that is very sharp and that holds up well over time then you get my attention.
 
always shave against the grain. if you want it to shave really well you can actually induce a touch of sideways movement along with your 'scrape'. i dont mean a lot, but just enough so your strokes are gently sliding arcs as opposed to perfectly straight scrapes. kindof hard to explain.

if shaving off your arm hair gets addictive, you can take it a step further by switching to a straight razor for your morning shave. if you think something like a mach3 gives a close shave, you are sadly mistaken - i generally only shave with a straight razor every second day, since it shaves that close. a couple of my friends are the type that shave and already by lunch time they have 5 o'clock shadow. i got them switched over to a straight razor (heh, getting them to let me 'demonstrate' on them took a lot of persuasion) and now theyre a lot happier.

plus, theres nothing more masculine than using an implement that could flay your face of lop off fingers... i mean this is why they invented the safety razor in the first place :)

there are some threads around here i believe that deal with everything from choosing a razor (dont buy a new SS one) to how to use it.

and yes i agree that the 'shaving test' isnt a very good one to determine how well a knife will cut, at least not for an extended period of time. if you put too small an angle on your blade it will shave easily however wont be very durable. however, assuming that you know the right angle to sharpen your knife for its intended purpose, the shaving test is a convenient, fast way of checking if you have sharpened that angle well.

cheers,
-gabriel
 
[shaving / paper cutting]

DGG said:
You just need a very narrow blade angle.
Click to expand...

You don't need an acute edge, this just makes it easier.

I don't know what this proves ...
Click to expand...

If you can make the blade push cut newsprint and shave hair above the skin you can achive a level of sharpness which is greater than the majority of custom and production knives I have seen.

However the knife will not hold the edge very long.
Click to expand...

The sharper you make a knife, the more durable the edge will be in use, and the longer it will stay sharp.

-Cliff
 
I guess, there is some confusion about sharp edges, razor edges and edge holding.

First: If the knife has a large edge angle, you must hold the spine higher to cut the hair off. Thin knifes and small angles cut better. But that is no surprise.

For me shaving means easier cutting and a good finished edge, regardless of the angle.

I have noticed differences in initial sharpness, meaning shaving power from steel grade to grade. For example, Swamp rats 52100 with fantasy (or SR 101)
shaves best and i keep it at a large angle.

Depending on the steel grade this initial sharpness may change quickly. Meaning you will notice a dulling down from that edge sooner as if the edge was left less polished. But that doesn not mean, the sharper edge really dulls sooner or the duller edge will really dull later. It is only how ppl. notice it. If you leave the edge duller, you just come into the "dulling progress" at another point.

Some may say, the edge looses its initial sharpness and keeps a working edge for long.

So, a fine edge like a razor is not build to cut metal (angle) but the edge of a metalcutter can be finished to shaving sharpness.

Sharpness and durability can be considered by the force, which is needed to cut. A dull edge needs more force, so it is stressed more than a sharp edge.
 
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