The unsharpenable or is it just me? (plus your stories!)

G

GarageBoy

Joined
May 23, 2003
Messages
5,952
Ok, there's been three knives that's been through my hands that I deemed unsharpenable
1. My first knife the Gerber LST. I ground and ground and ground and never APPROACHED sharp. Verified by a buddy that it was a crapped out heat treat.
2. Opinel 7 that was at first GREAT, but as time went on and after a few touch ups, wouldn't take an edge. (guess it was softer towards the middle)
3. Today, I spent 2 hours trying to restablish something that resembled an edge on a early 1980s Buck 105 that literally had no edge. After 2 hours, I got something V shaped with an apex, but it wouldn't bite, no matter what I did, no burr or anything. Owner says that it's been through a grinder, he thinks, so I'm thinking the temper got ruined.

Any of you guys have similar stories?
 
I just finished up with an old stainless kitchen knife. It won't take a very acute edge without it breaking up, probaby because of grain size... Its also very soft and forms a burr to easily.
 
I was sharpening at a 40-45 degree inclusive angle. Didn't even feel like what an edge was supposed to feel like
 
You should be able to get almost any steel sharp, even annealed steel.
Heat treating is a method to keep the edge from getting dull. You are doing something wrong.
Bill
 
I have this kitchen knife that I can get wicked sharp, but then it loses its edge after cutting up like two carrots. I blame that on the heat treat. I've yet to find a knife that just won't take an edge - but some are definitely harder than others.

Shao

BTW, Leo - check your e-mail.
 
GarageBoy--

Are you sure you're sharpening the very edge? If your relief grind is a larger angle than your sharpening angle you'll hit high and not touch the edge. Your 3 examples indicate this might be your problem.
 
I was pretty sure I was hitting the edge. I saw my DMT coarse roughen up the very edge on the blade.
 
Oh I don't think it is just you. I think we all have our night mare knives that just don't want to cooperate when it comes time to sharpen it.

Mine are usually ATS34 or 154CM but I've also got a VG10 and a BG42 blade that are more difficult for some reason than others of the same steel. Sometimes I just give up and carry a different one for the day and come back to it later. Other times I'll give up the Edge Pro and go to the Razor Edge stones or give up on both of those and go with an EZELapp diamond. Whatever works gets the nod.

STR
 
What kind of sharpening equipment and what bevel angles were you using?

I have had some that had a wicked edge (for a couple of minutes).
 
Yep, I've gone through it.

I know any metal can be made sharp. But can is like "should, would could." Not necessarily easy, nor practical.

Some knives just take a finesse I'm no longer willing to put forth.
 
There are definitely knives that resist your best efforts. IMO burr formation has a lot to do with it .... I think there are just some steels, always stainless steels in my experience, that not only form large burrs, but that for some reason the structure of the edge is probably getting weakened or damaged a little deeper. So as we remove more steel, we're just revealing steel that's been damaged, while weakening what lies below it. At least that's my theory

I would recommend you try sharpening these stubborn knives using a rubber sanding block, the kind used for auto body work, with emery cloth. Use both edge leading and edge trailing strokes, and reasonable pressure to produce a somewhat convex edge. This method is the best I've found for steels that tend to get big, bad burrs, and some blades that otherwise just don't want to get sharp will respond pretty good. You can apply a microbevel with a Sharpmaker or whatever. Don't expect these dog blades to hold an edge real well, but you might still get some good use out of them.

BTW, rubber sanding block and emery cloth works great on good steel, too, and it's my favorite way to sharpen hatchets or dedicated choppers. After a while you get a real nice convex edge that holds up very well.
 
hmmmm over the years. usually had a knife that would not sharpen due to cheap steel, or improper tempering.
 
but that for some reason the structure of the edge is probably getting weakened or damaged a little deeper. So as we remove more steel, we're just revealing steel that's been damaged, while weakening what lies below it.
Click to expand...

Thats because stainless steels have much larger grain size then most other steels such as 1095 and such. At a certain point of sharpening angle acuteness, this takes effect as in your attempt to form a zero point (which is of course impossible but the closer you get the sharper it is) the grains break away. In effect you may as well be using an abrasive with the same grit size as the grains in the steel. Which can sometimes be massive.

In contrast very fine grained steels can take an excellent edge without breaking out.
 
Month and a half ago I was up at my place in Sebago and stopped into a Wallyworld for some stuff. Came accross a clampacked gerber airlight and a crosscut little multitool for 10$. I decided it would be a good beater for work and bought it.

First thing is that this was my first and last gerber I will ever by. I mean really a stick of butter was sharper out of the package. I really could not do anything with it so it sat in a drawer for a while. Yesterday I decided that I would just leave it in my work truck and beat the snot out of it but after spending a hour with the dmt stones over work I really could not get a edge on it. I usually sharpen all the guys knives at work but this one was the spawn of the devil. It now resides in a jersey barrier I was pouring and I hope it dies a horrible death.
 
ghost squire said:
In effect you may as well be using an abrasive with the same grit size as the grains in the steel. Which can sometimes be massive.

In contrast very fine grained steels can take an excellent edge without breaking out.
Click to expand...

Well, in general that is true, but usually those effects only appear at fairly small angles and thin edges. Most certainly not at 40+ deg. included. D2 as well as ATS-34 are among the coarser grained SS and both will easily get shaving sharp if they are treated and sharpened properly.

My own bain is 420HC. I can get it shaving sharp, but is takes forever. It seems to form a very rubbery burr that you can not really cut off, because it bends out of the way. Extremely annoying. I can strop it, but after a few cuts the edge folds over. Has very little retention.

Personally, I take an abrasion resistant steel like S30V over one that froms rubbery burrs anyday.
 
When I've seen this with blades, it always makes me think about how they say some stainless steels are "gummy" when being machined .... that kind of behavior would certainly seem to occur at a much, much more gross level than the size of carbides or normal steel grain.

I have to assume bad heat treatment is to blame when this happens, unless the manufacturer used a steel that's completely unsuited for knives.
HoB said:
Personally, I take an abrasion resistant steel like S30V over one that froms rubbery burrs anyday.
Click to expand...
Amen to that!
 
Well, in general that is true, but usually those effects only appear at fairly small angles and thin edges. Most certainly not at 40+ deg. included. D2 as well as ATS-34 are among the coarser grained SS and both will easily get shaving sharp if they are treated and sharpened properly.
Click to expand...

Yes, I did mention that it only takes effect at a certain level of angle acuteness though.
 
GarageBoy said:
Thanks! I'll ATTEMPT to redo that Buck...
Click to expand...

What kind of sharpening equipment are you using? You said DMT course whetstone at 40-45 degrees. Did you use a finer whetstone later? There might be something in your technique that is affecting your ability to get a sharp edge.
 
You must log in or register to reply here.
Back
Top