The edge gets dull WITHOUT cutting?

B

bgentry

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Aug 3, 2009
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I was going to hijack the other thread about a knife that won't stay sharp, but my issue is different, so I'm starting another.

I have a Colt M4 folding knife by Fred Carter with a "Cryoedge" blade. All I can find on it is that it is "440 Stainless". A, C ? Who knows. Supposedly it is cryotreated.

http://www.knivesplus.com/colt-uc-ct98bknb.html

The blade came sharper out of the box than any knife I remember buying, though my collection is very small and I have only a few quality blades. It was shaving sharp for sure.

As I got better at sharpening and this knife got duller, I put a 15 degree back bevel on it and a 20 degree microbevel. I've kept it like that for a while, keeping the microbevel polished with a Spyderco white (fine) profile stone and finishing up on a strop loaded with green compound. It gets hair popping sharp, but nothing insane like some of you can do.

I've done some cutting tests with cardboard and it stays sharp after several cuts. Not hair popping, but still shaving sharp. So I'm pretty sure that I'm getting rid of the burr. I feel for it at all stages and try to even it out so it disappears with each grit.

FINALLY, my point: After I sharpen it and test it on paper and/or hair, I close it and leave it for a few days. Maybe I carry it or maybe it sits around, but I don't use the edge at all. After those few days, I open it and feel the edge and find it less than impressive. "Sharp" yes, but not like it was. Just today I opened it and found that it snagged in very light color ad paper, and shaved, but not impressively. When I put it away, it was much sharper.

I pulled out the strop and gave it maybe a total of 25 strokes, feeling the edge in between to see which side to work on more. After that, it pretty much popped hair again, and glided through that same ad paper.

I thought this was in my head the first few times, but it's repeatable. It keeps "going dull" without anything touching the edge. I have some whacky theories, but I can't figure out what's going on.

Any theories, experience, or suggestions? My good kitchen knives don't do this. Very odd.

Brian.
 
Ive got a few knives that do this as well. I'm very curious to hear the responses from those in the know. Possibly the steel "relaxing" to a duller state? I'll stay tuned.
 
You probably had a burr and when left alone the burr on the edge had time to corrode, thus creating a dull knife.
 
^ hmmm. Well, it keeps happening over and over so if that's true, then I'm not removing the burr correctly on this knife ever.

If I was able to cut say three or four times through 6" of light cardboard and it was still shaving sharp would that prove that I didn't have a burr?

I'm still confused.

Brian.
 
"Colt" knives are junk made in China. I had one once, and gave it away. "Cryo" probably means it was an untreated blade chilled in an ice cube tray.
 
bgentry said:
^ hmmm. Well, it keeps happening over and over so if that's true, then I'm not removing the burr correctly on this knife ever.

If I was able to cut say three or four times through 6" of light cardboard and it was still shaving sharp would that prove that I didn't have a burr?

I'm still confused.

Brian.
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It wouldn't prove that you had a burr or not because its a coarse material and causes a slight bit of damage to the edge but if the burr is large enough to effect performance then it would probably end up being very pronounced to one side.

I think RF has a better answer though. ;)
 
I have experienced this with a number of knives, mostly 420 stainless or equivalent. I have not experienced it with carbon steel knives. I have no explanation. Sharpened knives, sitting untouched in a showcase, getting dull. Only slightly dull, but nonetheless duller.
 
I've had this happen to a few knives. It must be a result of the individual steel itself as it doesn't happen with all of my knives. After I sharpen, if I'm just putting the knife away, the blade ALWAYS gets treated with Marine TUF-CLOTH, (a dry-film rust inhibitor) and the pivot gets a shot of TUF-GLIDE, so I'm pretty sure that there is no corrosion occurring at the edge. But there is no doubt that some of the blades do lose quite a bit of that really finer cutting ability... Sort of the difference between when you finish your sharpening with an extra fine stone or finish up with a strop. Really quite noticeable.

Stitchawl
 
Some sheaths will let the unknowing slightly dull the blade while putting the knife in the sheath, and some more while moving it around.
 
Bill DeShivs said:
I have experienced this with a number of knives, mostly 420 stainless or equivalent. I have not experienced it with carbon steel knives. I have no explanation. Sharpened knives, sitting untouched in a showcase, getting dull. Only slightly dull, but nonetheless duller.
Click to expand...

Have no idea how you are dulling yours. If we only had a professional knife maker to ask??????????????????????????????????????????????????????//
 
Just a thought.. but is it possible that the edge is touching the bottom of the inside of the handle, or something inside the handle ever so slightly?
 
Just because its 440a means nothing, its still a stain-less steel.
 
knifenut1013 said:
Just because its 440a means nothing, its still a stain-less steel.
Click to expand...

I understand your point, but 440a is a "highly" stainless steel so im still going with my gut feelings until i find out the "op" lives near the sea and stores his knives in a salt water tank.
 
Joe Talmadge addressed this in his article on sharpening and the need to steel the knife often . Stating that the sharpened edge will curl . DM
 
The best explanation I've heard is memory.

(Warning! This is the most exhaustive sharpening FAQ I've ever seen.)
http://forums.egullet.org/index.php?/topic/26036-knife-maintenance-and-sharpening/

If you don’t use a steeled edge right away it can actually relax back into its blunted state. The same is true of a blunted edge. If you really degrade the edge of your knife in a heavy cutting session, let it sit overnight before sharpening. It will be in much better shape than it was the day before.
Click to expand...
 
all edges will get "duller" over time due to corrosion at the edge (not always visible). I've had scary sharp knives become just paper slicing sharp over years. a bit of a disappointment but I normally just strop it a little to get rid of the corrosion and get back a little of the original edge.
 
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