sharp, sharper, sharpest?

[Daniel Rode]

Please help me understand this concept a little better.

I can get my chisels and irons pretty sharp. Sharp, for me, means and edge capable of pairing pine end grain or shaving the hair from a forearm. Assuming I was accurate in my honing and didn't round the edge, I understand that that's about the limit of sharpness. In other words, I've once I produce a zero radius edge, I've made the tool as sharp as possible.

As I further refine the edge, I'm polishing, not sharpening. This, as I understand it, makes the edge more consistent (smoother) and should provide the primary advantage of durability. A finely polished edge should make more cuts before becoming dull. A secondary benefit should be a smoother cut due to reduced friction. The edge feels sharper because it take less effort and produces a (microscopically) smoother cut.

The practical application has to do with how far to go after the initial sharpening. One could stop at 5-10 micron (4k range) polishing and have a usable tool or go up to .5 -1 micron (8k) and have an edge that lasts longer. Stropping, then is nothing more than even finer polishing of the edge.

I probably misused a technical term or two, but is this generally correct?

[John Coloccia]

I think it's more of a maintenance thing. If you strop or otherwise "hone" a lot....and every 5 or 10 swipes is not too often depending what you're doing....you will maintain that sharp edge for a LONG time with very little effort. For the weekend warrior, it doesn't matter. If you're trying to make a living at this, you can't afford to be going through some sort of sharpening ritual ever hour or two. You need to get the tools SHARP once and for all, and keep them that way for a long time.

[Prashun Patel]

"Once I produce a zero radius edge, I've made the tool as sharp as possible".

It was explained to me this way:
Your edge is not truly zero radius unless both intersecting planes (front and back of the blade) are truly flat. If they are 'rough' then they will not meet cleanly along the entire length; it will be sporadically zero radius. That means only parts of the edge are doing their job. This puts more stress on the points that are truly meeting the edge, and causes the regions to the immediate right and left of such points to be lifted laterally instead of sheared. That's why the blade wears faster and risks more tearout.

Is this how you guys understand it?

[John Coloccia]

It's a matter of scale. You CAN'T get to 0 radius, because no crystal is perfect, and if it was then no atom is 0 volume if for no other reason than Heisenberg's uncertainty principle. So how do anyone measure 0? Anyhow, you won't approach any of this in a workshop, so it's not a matter of 0...it's a matter of "good enough" and that's all it will ever be. For me, good enough is if I can take a good number of swipes, strop for maybe 10 seconds, and go back and take another good number of swipes. That's sort of my practical definition of sharp enough.

[John Coloccia]

Incidentally, I dont mean that last post as a "bucking popular knowledge smartypants" post. It's more a matter of most of us not having any way of measuring or analyzing any of this in any sort of scientific or rigorous way, so why not simply use some sort of practical measure instead of worrying about particle sizes and things like that.

[Don Dorn]

I guess everyone has their own way. In my case, worrying about 0 radius isn't something that can be quantified. I think one must be able to sharpen quickly or you won't do it when it needs to be done. There are many ways to acheive great sharpness, and to test, I once used receipt paper and knew I was there when the iron "wanted" to slice it nearly in half. That takes too much time so now I simply place the edge against a finger nail and determine if it "sticks" at a very low angel. If it does, it's certainly sharp enough for anything I've wanted, because that level will also slice the receipt paper as well. If it doesn't (and it does), you would know immediately and before you would cut into a cuticle.

[Dave Anderson NH]

How many angels can sit on the head of a pin?

Rather than try to quantify how small a radius you can get at the intersection of two planes lets go the opposite and easier to identify way. A close friend who is, an expert turner, NH Furniturmaster, and former shop teacher has a nice workable definition of dull. A cutting edge becomes dull when there is a radius of .00025" which in the small included angles of our cutting tools pretty much equates to a .0005" "diameter". Note the parentthetical use of diameter since we are not talking about a full 180 degrees.

I think Daniel has the concept pretty well down. I have always said that super sharp is a moving target. What you consider sharp as a beginner will seem inadequate as your experience and skills increase.

[John Coloccia]

What you consider sharp as a beginner will seem inadequate as your experience and skills increase.

THAT should be a sticky. Getting to "sharp" gets so much easier with practice, and all the hand wringing seems to magically melt away. It's like grabbing "impossible" chords on a guitar. With a little practice, they become easy and then you start worrying about what to do with them

[Daniel Rode]

To clarify, I'm trying to figure out when to stop sharpening and get back to the real work of cutting wood.

Assuming good technique, a 4k stone can produce a sharp/fine/polished enough edge to be effective. That's not the case with a 1k stone. How much tangible improvement does one get on an 8k stone? How about 16k? 20 strokes on a stropping block? Maybe 1k, 4k and a quick run on the strop is a a good compromise?

I also understand that some of this is subjective and will, vary from person to person. It's not unlike harder vs softer iron. One is easier to sharpen but quicker to dull the other take more effort to sharpen but holds an edge longer.

[Chris Hachet]

I find about 8K right....I can cut the hair on my arm or get curls on the end grain of Hard Maple.

[John Coloccia]

To clarify, I'm trying to figure out when to stop sharpening and get back to the real work of cutting wood.

Assuming good technique, a 4k stone can produce a sharp/fine/polished enough edge to be effective. That's not the case with a 1k stone. How much tangible improvement does one get on an 8k stone? How about 16k? 20 strokes on a stropping block? Maybe 1k, 4k and a quick run on the strop is a a good compromise?

I also understand that some of this is subjective and will, vary from person to person. It's not unlike harder vs softer iron. One is easier to sharpen but quicker to dull the other take more effort to sharpen but holds an edge longer.

Just my opinion:

Typically, you'll see an improvement on an 8K stone, if for no other reason than it's faster than a strop. I have a 16K stone that is nearly unused. I see no real benefit.

But that's just my opinion, and that's just with the stones I happen to have. 8K on one stone is not the same as 8K on another. When I used stones, I went to 8K on a Norton. Now, I just use Spyderco ceramics, thanks to George, and I don't know what the "k" is. I use the "fine" and "ultrafine", and then strop to maintain it, plus I use a Worksharp 3000 to establish/fix my bevels.

I have one strop charged with Simichrome, and others that are just bare leather.

[Tony Shea]

From a 4K stone I really think you would appreciate the nicer edge off an 8k stone. But in reality some green honing compound (the stuff LV stocks) on some leather, MDF, etc will certainly get the job done as well. If you are hesitant on spending the $ on another finishing stone then the honing compound is no doubt going to give you a much nicer edge than stopping at the 4k stone. It's also very handy in maintaining your edge between sharpening as John mentioned. If you can get in the habit of hitting your strop more often than you think is reasonable then you can really go quite a long while before you need to start over.

[Brett Bobo]

Hi Daniel,
I'm sympathetic to your questions because I was there not too long ago and this whole sharpening thing was overwhelming. I think it's best if you just simply try out several procedures and determine for yourself what serves you best. Do a trial and error with various ending grits and see what works and what doesn't. Personally, I would continue through a 8,000 grit stone but I've started stropping using a honing compound on a piece of soft maple as well. Also, keep in mind that when you're only honing, this procedure should only be a matter of a few minutes so stepping up to a 8,000 grit stone or even stropping isn't adding but a couple of extra minutes at the bench. Enjoy it and you'll have that "ah-ha" moment soon enough.

[Federico Mena Quintero]

To clarify, I'm trying to figure out when to stop sharpening and get back to the real work of cutting wood.

When the tool is sharp enough for your purpose. A mortise chisel doesn't need to be as scary sharp as a paring chisel; a jack plane doesn't need to be as sharp as a smoothing plane; etc.

See http://www.toolsforworkingwood.com/s...0Tool%20Sharp? for an interesting analysis of the sharpness of carving gouges, for example.

[Jim Matthews]

I sharpen all my edge tools the same way, with the same four media - always in sequence.

I think Frederico is correct in the regard that the precision required for different cutting edges is according to the procedure.
In practice, I sharpen everything the same way, so the finer tools stay sharp longer and the coarse ones are always on the stones.

Whatever method is chosen, it's important to be consistent and concise - so you can get back to it.

I only wish I could file my saws as fast as I can sharpen a blade.