How do you tell if the edge you are sharpening is as sharp as it can be?

G

GarageBoy

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May 23, 2003
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I'm working on coarse diamonds and I like the edge it creates, but working on this LST, I can only feel a little toothiness. It doesn't grab much. When I hit that edge with ceramics, it makes the knife TOTALLY dull to the touch. I already thinned down the edge big time.
 
Learn to see and feel the wire edge ( burr ).
When you have got to the sharpening stage that you can flop the burr from side to side, then you need to remove the burr with the ceramic at NO MORE THAN 2° greater angle. These last few swipes with the ceramic must be oh so light. Just kiss the edge.
 
The very most important piece of sharpening equipment is not a stone or diamond-impregnated thing, or a jig of some sort. No. The very most important piece of sharpening equipment is some sort of loupe or microscope that allows you to see the edge at least 10X. Now, you'll be able to see and understand the affects of your efforts.
 
Hold on here! What to you mean working on an LST with coarse Diamonds. Did you get your stuff back? Inquiring minds want to know...

John
 
Go to Radio Shack and get their lighted pocket microscope. For around $10 US, it is variable from 60X-100X. I love mine! G-10 looks cool :cool:
 
GarageBoy said:
How do you tell if the edge you are sharpening is as sharp as it can be?
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You get someone who knows how to sharpen really well to sharpen the knife, you then have something to use as a reference. Or buy a well sharpened knife. There are some custom makers that are known for high levels of NIB sharpness, like R.J. Martin, in the production area Spyderco wins easily for NIB sharpness.

Of course buying a gaggle of Sypderco blades just to get an idea of sharpness is kind of expensive (but the knives are nice to have for other reasons), a more inexpensive way is to buy a package of Olfa snap-off blades. Any knife you buy (aside from the made in Taiwan knockoffs) should be able to get as sharp as those Olfa blades.

That Radio Shack magnifier number is for *AREA* magnification, the other numbers quoted in the above for the loupes and such are linear magnification. In the same scale the Radio Shack magnifier is up to 10x .

-Cliff
 
Can it shave arm hair?

Then it's plenty sharp. No need to fret about getting it "more sharp".

The only way to get more sharp is to sharpen on progressively finer and finer abrasives. This gets ridiculous very quickly.

In building architectural models, we toss our exacto blades after 10 cuts or so. We have to have near-perfect sharpness to make very precise cuts. A dull blade could mean tossing a detailed facade with a few hours work in it. Better to just get a new blade.

The point of the lil' story is that sometimes ultra sharp is ridiculous. You'd end up spending more time maintaining it than actually using it.
 
I like ordinary newsprint as a medium for assessing the state of an edge.

A slow draw-cut through newsprint will reveal nicks, chips or irregular sections that are difficult to spot visually, from the base to the tip of the edge. You get feedback audibly (cutting/tearing of the fibers), visibly (small step-changes in the cut) and you can sense small changes in resistance.

Straight push-cuts at various points along the edge will quickly reveal problems such as the belly being sharper than the tip or base of the blade.

There's a PROBLEM with relying totally on newsprint as a testing media, in that a 'sharpened wire-edge' will not be revealed by newsprint

I test for wire-edge by several forceful slow draw-cuts into a hard substance (the harwood base of my strop or the hard plastic case supplied with Spyderco stones or Sharpmaker). A wire-edge will collapse under the pressure of several draw-cuts under strong force.

After testing for wire-edge, a blade should drift through newsprint with a just a whispered 'hiss'. Quieter = sharper.
 
pendentive said:
The only way to get more sharp is to sharpen on progressively finer and finer abrasives.
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Sharper does not equal more polished

You can have an edge with a coarse finish which is sharper than an edge with a high finish.

I have seen edges off of 100 grit AO belts which could shave hair above the skin.

Sharpness is a matter of edge alignment, uniformity, and lack of defects (dents, chips, rust, etc.) .

... sometimes ultra sharp is ridiculous. You'd end up spending more time maintaining it than actually using it..
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I think you need better steels, in general if you are looking to maintain very high levels of sharpness move out of stainless and into tool steels with very fine grains and high levels of hardness.

Plus of course your ultra-sharp knife will eventually just degrade to a regular shaving sharp knife, it doesn't jump from ultra-sharp to dull. So it stays sharp longer, not shorter as it has that extra lead.

Of course if it is *very* difficult for you to get ultra-sharp then you have to balance this against the gains, of course a lot of such problems are due to the way in which the blade is ground, unsuitability of the steel to the type of blade, etc. .

Sharpness is also only one factor in cutting ability, for some knives it isn't one of the critical elements (wood cutters), however on some blades (flimsy material) it can be quite critical.

-Cliff
 
Your problem is the particular steel used in the LST. I don't know what it is, but it sucks. I suspect a cheap 440A equivalent with a bad heat treatment. I noticed the same problem. I think that the grain structure doesn't support a fine edge. If you have a fine diamond hone I would use that as my last step rather than using the essentially extra-fine ceramic hone. The diamond will groom the large carbide grains and/or give you a toothy edge. The ceramic just sort of pushes things around.

If you don't have a fine diamond hone try finishing with about 220 grit Wet or Dry paper. Use new paper so that the grit is sharp. Put it on something smooth and hard and use it like a bench stone. If you don't like the way that it works after 220 try going coarser or finer.

In the end the best test of sharpness is whether it cuts things for you. I like to see if I can whittle through an old leather belt and whether I can sharpen pencils without breaking the lead. Cutting paper is helpful as well. With a steel like the LST it is very hard and not very practical to try and get a shaving edge.
 
You may feel that the edge will never be as sharp as it can be, but don´t be too obsessive about it, match the type of edge to the use and be happy.

For years I´ve used an 8X Loupe, I have recently acquired a 20X and a microscope type 30X but still like the 8X.

I like Cliff comments on edge alignment, uniformity, and lack of defects.

I like Jeff instructions on how to sharpen (but I don´t feel so bad about 440A).
 
The steel on the LST is a 420 series I think. Very soft. But what do you want for $20? An LST was one of my first knives, but I could get that thing damn sharp. I even used to shave while my brother drove me to a job interview because I'd forgotten to. That was with a $4 Arkansas wetstone. Decent knife for a throw-away beater.
 
Time and again, on this site and others, I've seen guys say they couldn't get some blade sharp until they ground a certain amount of steel away, then the blade sort of magically changed. It seems to be caused by heating when the edge is ground during manufacturing. You have to get rid of the bad steel and get into the good stuff. I had it happen with a CRKT Mirage. Could be what you're up against.
 
I got this thing for $20 and it was meant to be my sharpening practice! And yes, I got my stuff back for now. It's 420, and I remember it having a half decent original edge.
 
GRMike said:
Time and again, on this site and others, I've seen guys say they couldn't get some blade sharp until they ground a certain amount of steel away, then the blade sort of magically changed. It seems to be caused by heating when the edge is ground during manufacturing. You have to get rid of the bad steel and get into the good stuff. I had it happen with a CRKT Mirage. Could be what you're up against.
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I have a Benchmade 705 in D2. The NIB edge was THE WORST edge I have ever seen - grossly uneven bevels and a HUGE burr that just flopped from side to side. I've reprofiled to Sharpmaker 30/20 specs. I now have a very good edge but it could be better. It's just taking me some time to get to know how D2 works. Every blade/steel has it's own personality. Some just seem to "reveal" themselves more readily than others. ;)

Concerning the LST. I have a small one that takes an edge on the Sharpmaker with aplomb. It just needs more frequent steeling/touchups than the higher quality stuff.
 
It's not an original edge. I ground that off months ago trying to "sharpen" it. When I hit it with coarse diamonds, it barely bites into my finger when I pull it across.
 
GarageBoy said:
When I hit it with coarse diamonds, it barely bites into my finger when I pull it across.
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Well that's the problem. You shouldn't be hitting your knife with the stone. Try running the edge across the stone instead :D!.

Seriously........ It sounds like you aren't getting a burr formed.
 
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