How sharp is sharp

[Nicholas Lingg]

I know this has been discussed before. Ive looked at a lot of prevous sharping theaded but could not find an answer. When a chisel is sharp enough to shave the hair on your arm, does it have to be any sharper?

[Mike Henderson]

There's differences in how an edge will shave hair. At the low end of the scale, you push hard against the hair and it eventually cuts the hair, with a lot of pulling of the hair in the process.

At the upper end of the scale, you just lightly stroke the edge against your skin and the hair is cut off.

But that doesn't mean that every edge should be at the upper end of the scale. A paring chisel should be very sharp but a mortise chisel might do very well at the lower end of the scale.

Mike

[John Finley]

IMHO, being able to shave hair on your arm is fairly sharp, and probably sharp enough to do most chisel work. With that being said, shaving hairs does not mean that it is as sharp as it gets.

I have never realized this more than when I recently went to a waterstone sharpening system. When I get done with my planer blades and chisels and the waterstones/MKII, there is a noticeable difference between that sharpness level and what I was able to do prior to waterstones. But I was still able to shave hairs before the waterstones. I am kind of rambling here, but I am trying to say is that shaving hair does not mean that you can't get a blade any sharper.

[Jeffrey Makiel]

I use waterstones also. But only for hand tools like chisels and planes. The highest I go is 6000 grit with no further honing. Machine blades and knives are sent out or simply replaced with new.

-Jeff :)

[Tom Walz]

When testing how long woodworking tools stay sharp, one measure is the radius of the cutting edge measured in microns.

[John Coloccia]

For me, the chisel's sharp when it can do it's job consistently, For a pairing chisel, that means slicing through the wood with consistent force. For a mortise chisel, that means going down the same amount on each hammer blow. I know that the wood itself has variability in it, but it should be obvious when it's gone from sharp to dull. Dull tools operate inconsistently, and that makes them dangerous to you and your work. Well, at least to me and MY work. I'm sure skill can overcome a lot!

My japanese chisels can literally split hairs. It's quite an amazing thing to see. My western chisels and planes get sharp enough that they shave (not quite hair splitting sharp). My mortise chisels are not quite this sharp. They start off like that, but the first few bangs take just a little bit off. They're still quite sharp, though.

[brian c miller]

+1

Sharp in terms of microns is out of the reach of most people. I don't have a 200x microscope to look at the radius. I do have a block than I can perform a few test cuts and back then it's back to work.

A reasonably sharp cutting edge is much much safer than a dull one.

[Glen Butler]

Oh, you don't want to just shave hair you want to split hair:D Get to that waterstone and go at it.

[John Thompson]

I use scary sharp because the system is cheap.. simple.. quick and probably the least messy. I hand hold without a jig. I don't have a clue what true degree my chisels or irons are to be honest using a hand hold as I don't check them. I have never gone over 2000 grit in polishing and edge on any of them.

When I reach the point that a chisel or plane iron will shave end grain on hard-wood I know the chisel or iron is sharp. And.. when it's sharp.. it's sharp! So... instead of fret over could it have been made sharper I simply put it to work! My chisels or irons have never failed me yet using this approach and don't expect any surprises. :)

[Jeff Duncan]

I'm with John, I keep a block of oak or maple in my vise and when I can slice end grain it's sharp. Could it get sharper? Probably, is it going to cut the wood any better or longer? Probably not.
For me the point is to be able to use the tools to make something, not to spend all my time fussing with the tools. The less time spent sharpening the better.
good luck,
JeffD

[Dusty Fuller]

+1 on what John and Jeff said.

[Matt Radtke]

I prefer testing on the end grain of pine. If it's sharp, it'll cut. If it's dull, it'll smash the fibers.

[Don Dorn]

I've learned that I can get a blade to cut hair on my arm but won't slice receipt paper nearly all the way through without effort. That's my new benchmark now.

[Darnell Hagen]

I've stopped using the shaving test, my left forearm is a freak show. I can't wipe sweat off my brow, the stubble scrapes at my eyelids.

I prefer to pare softwood endgrain now.

http://thewayiwood.blogspot.com/2010/01/experiments-in-sharpening.html