How long should an edge last??

uilleann

uilleann

Joined
Nov 20, 2016
Messages
144
I have a several knives now with S30V steel blades. I put a 15 deg relief and a 20 degree edge. Both finished to a polished mirror. Cuts paper like nobody's business.

But then I use it to open some packages cutting through different kinds of tape and some cardboard. Easy cutting.

I go to cut paper again and its not nearly as sharp and gets caught up as I drag it through paper.

If I stroke it a few times on a ceramic hone.... its back to super sharp again.

So is this normal.... or should a paper cutting edge last longer before needing attention. And if its not normal then what might be the problem?

Thanks.
 
How did you sharpen them? Free hand? On a fixed angle jig? And your process of getting the mirror finish? 15 with 20 micro should give you very good edge retention.


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Edgeholding is very dependent upon steel, heat treat, geometry, media being cut, etc. What you describe for S30V should be a cakewalk unless there are other factors. Based upon what you described I am puzzled as well.

One fairly common condition that has similar symptoms is that you can have a micro-burr (some people call it a butcher's edge) that stays on the edge and gets deformed easily, but is also restored easily with a ceramic rod or butcher's steel. To get a durable edge, this micro-burr needs to be removed as it is too flexible. Not sure if this is relevant to your situation but the effect is very similar.

If the amount and/or type of cutting would not similarly dull a commercial razor blade I do think there must be something amiss with HT or sharpening.

Good luck,
Mark
 
I think you just got some glue on the blade from cutting thru the packing tape. That steel, even with that edge, should cut thru several hundred linear feet of corrugate cardboard. Sharpen it to only around 300 grit and it will cut more. DM
 
Hi,
How many times have you sharpened this blade?
If its not a burr (check by deburring at double angle)
its probably a burnt/fatigued edge
solution is cut off the edge and sharpen again
and repeat until it survives a couple of hundred cuts through cardboard
 
Mark Schmitt said:
Edgeholding is very dependent upon steel, heat treat, geometry, media being cut, etc. What you describe for S30V should be a cakewalk unless there are other factors. Based upon what you described I am puzzled as well.

Good luck,
Mark
Click to expand...

I am as well that's why I am curious to find out how he sharpen them, may have been over-strop to achieve mirror finish, maybe the bur is still there,... just too many variables to conclude.



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I'm betting on glue from the packing tape. Gums up my blades every time. Doesn't matter whether it's super steel or a butter knife.

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MAD777 said:
I'm betting on glue from the packing tape. Gums up my blades every time. Doesn't matter whether it's super steel or a butter knife.
Click to expand...
Hi,
Does a few passes on a ceramic hone remove the glue when that happens?
Does the glue stick to the hone?
When I get glue I try wiping it off and cleaning it with oil or soap or hand sanitizer... didnt want to try cleaning the hones
 
bucketstove said:
Hi,
Does a few passes on a ceramic hone remove the glue when that happens?
Does the glue stick to the hone?
When I get glue I try wiping it off and cleaning it with oil or soap or hand sanitizer... didnt want to try cleaning the hones
Click to expand...
Soap & water & elbow grease! ;)

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Haha yup, that's why you don't mirror polish a pocket knife.

I still do it though because I enjoy the sport of sharpening.
 
Thanks for all the replies. I had sharpened it with the KME system. Diamond stones thru Chosera stones up to 10000 grit. I then got a ken onion work sharp with blade grinder attachment. I did do a resharpening at the higher grit levels just to see what it was like. I also made a leather backup to the vertical side of the attachment and used it to polish the sides of the blades. Lookes nice. To finish it off I went back to the kme to refinish the edge. I had to go back to the 300 grit stones to get a burr. And then went through all the stones to 10000 again.
 
Your reducing the edge life with that much polish.

If you want better results like you read about in ankersons steel testing thread. The do a 15dps 400 or 600 edge fully deburred with no mirco bevel and a loaded strop finish, that is all.
 
bucketstove said:
Hi,
Does a few passes on a ceramic hone remove the glue when that happens?
Does the glue stick to the hone?
When I get glue I try wiping it off and cleaning it with oil or soap or hand sanitizer... didnt want to try cleaning the hones
Click to expand...
That glue is pretty tenacious. Oil works great for releasing glue. Even nose grease will work lol. Then final clean with alcohol or some other solvent.

Heads up. Even when you think you got it all, a bright light will reveal its stubbornness. It really hangs on to the very edge, where common sense keeps you from scrubbing hard.
 
Last edited:
Acetone works very well for removing tape adhesive residue. No scrubbing or even pressure necessary.
 
Cardboard is one of the most abrasive materials you can find. It will take a fine edge off very quickly. A coarser edge might last longer, but maybe not. Box cutters with replaceable blades work best for that chore.
 
Very true, but my 8cr13mov tenacious will still shave after doing what the OP described.

My money is on the micro burr if glue isn't the problem.
 
DeadboxHero said:
Your reducing the edge life with that much polish.

If you want better results like you read about in ankersons steel testing thread. The do a 15dps 400 or 600 edge fully deburred with no mirco bevel and a loaded strop finish, that is all.
Click to expand...

agreed
 
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