Can some knives CANNOT be sharpened?

golok

golok

Joined
Oct 20, 2000
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I have been experiencing some unusual problems with some knives. No matter how much time I spent on sharpening them, they remain fairly blunt.

I don't think there's any problem with the Sharpmaker 204. It is a wonderful device. I am puzzled by this phenomenon.

Surely, even a blunt knife can be sharpened after a while. I don't seem to have any problem with my other knives but there are these two or three blades which have stumped me.

Why?
 
The sharpmaker has its rods set at a pre-determined angle; if the knives you are sharpening have an angle sufficiently more obtuse, than it will take a lot of work before you have reprofiled the edge to the point where the sharpmaker will be working on the actual edge itself, and not the area above it. Have you tried free-hand sharpening? That, at least, allows you the ability to vary the angle at which you are sharpening.
 
Certainly - our old kitchen knife. :D

I've tried all possible (and impossible) sharpening methods but no help.

Tuhkis
 
An Edge Pro will make quick work of reprofiling the edge. Then you can maintain the edge easily with the Sharpmaker.
The Sharpmaker will take forever to reprofile an edge angle.
Lenny
 
I've heard that Spyderco is coming out with diamond-coated stones for the Sharpmaker after the first of the year..It should make re-profiling quite a bit easier. As stated, Golok, that's your problem. The Sharpmaker is difficult to use when a major re-profiling becomes necessary. Watch for those new stones.
 
Surely, even a blunt knife can be sharpened after a while.
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Nope. Depending on what the blade is made of and depending on the heat treatment, that may not be true.

Take ATS-34 as an example. It's well-known for taking and retaining an excellent edge. But, that is true AFTER it receives a proper heat treatment. Even a high-quality manufacturer may accidentally ship an otherwise excellent knife that has a heat treat problem. And that's an outstanding alloy.

Some charming China Cheapie knives have blades made out of pot steel. You'll probably never be able to get a good edge on that.
 
You should be able to put an edge on any metal. Whether it holds the edge or not is a matter of heat treat. Wayne Goddard talks about a guy in one of his books that made a knife for his journeyman smith rating (I think) and passed the rope swing cut. After that, the blade grossly failed. It turns out that the guy used MILD steel!! OOPS! But the incident showed that even mild steel can take a rope cutting edge. So, even your odd knives ought to take a hair shaving edge. Whether or not the edge stays is another thing.

Try the magic market trick. Coat the edge with magic marker and make a few passes on your sharpmaker. If the very edge is shiny, you are doing alright. If there is still ink on the very edge, the shoulders of the edge are too thick and need thinning out.

Good Luck.
 
golok, were these problem knives ever sharp? If they were, they can be resharpened. If not, they may be made of poor materials and edge geometry, and not worth the effort.

Try this: use Crayola's technique with a magic marker. Set the Sharpmaker to 40 degrees, and then sharpen again at 30 degrees -- probably do the thirty degree strokes twice over.

If they still give you grief, consider retiring them to the butter knife drawer!
 
I have owned a cold steel voyager and an old sytle Endura
that I could not get sharp for the life of me, didn't try
a sharpmaker though.
 
I have two Gatco Tri-Seps, one ceramic and the other diamond-coated. They really are like short sections of Sharpmaker rod, with a groove down one face for darts or needles, and one edge rounder than the others.

I had sharpened my S.W.A.T. butterfly in 154CM a couple of times, but I couldn't get the tip sharp. The problem was, I was pulling away from the Sharpmaker rods at the last moment, to keep from rounding the tip.

So I sat down with the Tri-Seps and carefully buffed the bevel at the very tip, first with the diamond and next, gently, with the ceramic. A perfect razor edge!

Sometimes you just have to vary your routine. No one system works for everything, even though I find the Sharpmaker comes close. I do keep my knives sharp, so reprofiling generally doesn't enter into it.
 
Zoso, the Sharpmaker will do Spyderco serrations, of course, of course. Quite possibly, nothing will sharpen Cold Steel serrations. :) What I do to keep my Vaquero Grande slashing-sharp is to use a steel on the flat side of the blade, opposite the serrations. It straightens them out well enough to restore the edge very nicely.
 
Golok,

I use my Sharpmaker on my good knives that already were pretty sharp to start with. They work well but don't remove metal quickly enough if you wanna do major changes to the edge. Took me forever to reprofile the edge on one of my Benchmades with an ATS-34 blade.

For my parang and POS knives made of unnamed steel i use a large coarse whetstone that removes metal much quicker than the ceramic sticks.
 
Crayola :

You should be able to put an edge on any metal.
Click to expand...

Some metals are very difficult to hone properly because they have a very large grain size and inconsistent make up they break apart very easily at the edge, try some of the Al alloys for example.

It turns out that the guy used MILD steel!! OOPS!
Click to expand...

Mild steel actually makes a decent blade steel for soft materials, I know a maker who uses it for knives on occasion.

Golok, while most blades can be sharpened well, there are lots of ones that make life very difficult do to edge geometry or materials issues. For example really soft steels like 420 suffer edge burring badly and thus you need really crisp and clean hones and a light touch, the Cobalt superalloys behave in a similar manner.

On the other side of the spectrum, harder steels ( 62+ RC) can be brittle at the edge depending on the heat treatment and at low angles will break apart easily, so you want a soft stone with a suitable binder like Japanese Waterstone and again go lightly on the final work.

There are also lots of problems that are very difficult to spot. A simple magnifier that will let you look at the edge even under 10x magnification will make life a lot easier as you can see how the edge is developing as you move to finer grits.

For example if the edge of the blade has been burned badly by over heating during grinding you will note under magnification that it is breaking apart badly. You of course need to reference the appearance against a knife that you can sharpen well.

-Cliff
 
Esav: I think Lansky makes a litthe ceramic stick that fits Cold Steel's serrations now. You have to sharpen a small section at a time, but I think this looks to be worth the investment.

Cliff: Thanks for clearing things up a bit, and also raising more questions! Indeed, I didn't mean "any" metal. I meant any metal typically used in knives. Even the United Cutlery Gil Hibben fantasy stuff ought to take an edge. Whether it holds the edge is another matter. Same goes for mild steel. It can take an edge, but edge holding is extremely low, don'cha think??

Cliff, what kind of knives does the person you know make out of mild steel? I am very curious to find out as it seems to me mild steel knives wouldn't be all that useful.
 
One other type of edge that I found I could not sharpen was a knife with a badly rusted edge. I ended up using a power drill with sanding disc attachment to remove a lot of metal. Only after that could I get a good edge on it.
 
I have a Gerber dagger bladed necker. It wasn't sharp when I got it new, and I was never able to get an edge on it with my Spydie 204. The bevels looked proper. I turned it over to a professional hunting guide who is the best sharpener I know. He worked with it for a couple of hours with no improvement. I think if you get a bad heat treat, nothing is going to work. This thing sits in my drawer because I would be too ashamed to ever sell it. "Knives don't slice people, dull knives slice people"
David
 
CERAMIC KNIVES! I have back an old ceramic paring knife I gave to my Mom years ago when they first came out. About a 1/4" of the tip is broken off, and it is nowhere near as sharp as it was new. I think Mom probably was a little careless with it - like maybe she cut things right on the tile countertop instead of a cutting board.

I've heard that you can restore the edge with a diamond sharpener, but I've been working on this sucker off and on for about a year (really) and I'm just not seeing any edge coming back. Just bought a new ceramic paring knife by Boker, that she can only use under my watchful eye!;)
 
A book called "The Razors Edge", cannot for the life of me remember the guys name, is a great source on how edges work, and how to make them work for you. I read it over and over, then gave it to my dad. He got a bit upset when I was able to get better edges than him:D .
We now are both capable of puttin an edge on that you can dry shave with, granted an edge of that caliber is senstive to hard use. Good luck with the knife.
 
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