Getting a razor edge, but losing it quickly, what am I doing wrong?

[savasyn]

Hello all,
I've recently taken a huge leap in my previously pathetic attempts to sharpen blades by picking up a Spyderco Sharpmaker. Thankfully now I am getting something between very usable and pretty impressive(for me, at least). As I'm still very new to all of this, I definitely have a LOT to learn, so I joined this forum

Quick question about the results I'm getting though. I find that with decent steels(I had been practicing on some $5 junk knives with very questionable blade materials), I can get a really impressive edge(for me at least) but that it doesn't last more than a few cuts. To be specific, my EDC is a Spyderco Ambitious with 8Cr13Mov(arguably the best steel I've attempted to sharpen so far) takes a razor sharp edge off the ultra fine stone and strop block but loses it after a few passes through cardboard. It's still quite usably sharp at that point, just not what it was minutes before. Is this to be expected with this steel against cardboard or am I most likely doing something wrong?

In the "am I doing it wrong" department, when I sharpened my Ambitious, I used the 40 degree angle per the instructions. I've since read that Spydercos come with a 30 degree edge from the factory so perhaps I should have used the 30 degree angle to sharpen for consistency. I just read through a couple of threads on micro bevels, and it sounds like I might have done that inadvertently to this knife. If that were the case, shouldn't I have better edge retention with the less acute angle? If I should have stuck with the 30 degree inclusive, is there a safe and simple way to get back to it at this point for someone of my very limited skill? I do have the diamond stones for the Sharpmaker in case those might be needed.

Hopefully that all makes sense. Perhaps this is all just a phase new sharpeners go through, especially with less tough steels like 8Cr13Mov. We get all excited when it works and want it to last, but perhaps that steel just can't maintain a razor. As I said before it's still quite sharp, just noticeably not what it is right off the stones.

Thanks in advance for any thoughts or advice!!

 

[100eyes]

kinda depends on the cardboard. some will dull the edge faster than others. many can and do eat an edge pretty quick, but it does depend on your idea of sharp and dull.

personally I've never had the Sharpmaker or seen it's instructional videos, but I suspect it's a lot of techniques and not enough fundamentals of sharpening.

 

[rdnkbkr]

Cardboard can and will dull a knife very quickly, even on really high grade steels.

 

[richard j]

+1 on cardboard dulling an edge. one thing you might try is a convex edge. i made a knife for a member and put a convex edge on it. he told me he uses it to cut up cardboard boxes he puts his groceries in and what used to take him several knives to cut up the boxes now only takes the one i made him.

 

[2 shot]

Don't think you are doing something wrong, sharp is sharp no matter how it is done. If the entire length of the blade is equally sharp the goal has been met. I am sure you know the hardness of the steel is a big factor in how long it retains a sharp edge.

After slicing the cardboard can it still cut phone book paper efficiently?

 

[Obsessed with Edges]

I'd bet there's at least a little bit of wire edge contributing to the initial sharpness, which gets scrubbed away or folded over in the cardboard. Coming off the ceramic (Sharpmaker) especially, it's very easy to create a wire, even likely it'll be there. Stropping by itself usually won't remove them.

As mentioned, cardboard can definitely dull an edge. And a wire edge will fail even faster in cardboard, which sounds to me like what you're describing.

 

[2 shot]

I'd bet there's at least a little bit of wire edge contributing to the initial sharpness, which gets scrubbed away or folded over in the cardboard. Coming off the ceramic (Sharpmaker) especially, it's very easy to create a wire, even likely it'll be there. Stropping by itself usually won't remove them.

As mentioned, cardboard can definitely dull an edge. And a wire edge will fail even faster in cardboard, which sounds to me like what you're describing.

A question for you. Will a wire edge cut phone book paper with out hanging up, and will one side of the edge feel sharper to the thumb?

 

[Obsessed with Edges]

A question for you. Will a wire edge cut phone book paper with out hanging up, and will one side of the edge feel sharper to the thumb?

A wire edge can sometimes cut the phone book paper, depending upon whether it's fairly straight (it'll cut), or bent way over or irregular/rough (it'll snag or slip). And you should be able to feel it on one side of the edge or the other, with a thumbnail or the tip of a needle or a sharp toothpick. Oftentimes, a wire edge that's leaning to one side will scrape leather or compound off of a strop, and the remnants will collect behind the wire edge, just as it might collect under your fingernails, if you scratched the strop with your fingers. Use a magnifier to look for traces collected this way.

If the wire is cutting paper, give the edge a few slicing cuts into hard wood (cross-grain) or something similar, then cut the paper again and see if the cutting performances changes. Look very closely when cutting the paper, to see where the edge slips or snags in the paper. Those spots are where to look for a burr or bent-over wire. If an edge is truly sharp and clean & free of burrs and wires, cutting the paper shouldn't diminish at all, after cutting into the wood a few times.

 

[Magnaminous_G]

Obsessed with Edges is probably right. If you look at a wire edge through a microscope (or a very powerful loupe), you will see that it is thin and toothy. It will definitely feel razor sharp. But it will soon be gone; cardboard will definitely get rid of it quickly due to all the hard particles and abrasive stuff in cardboard. Then you're left with an edge that is still unrefined (dull).

What can be done? Simple: spend more time on your coarser stones (if you've got a Sharpmaker, I highly recommend getting the diamond and ultrafine rods; they will set you back around $60, but totally worth it). Once you've gotten that wire edge off, then it's a matter of refining the edge: taking it down to the smoothest, glassiest edge with each progressively finer stone. But the key is to spend enough time with each stone until the edge is ready for the next level.

 

[2 shot]

Thanks!

Like the OP I use a Sharpmaker. (couple months now) I have never been able to detect a wire edge. I double up on reading glassed and use an old magnifying glass. I haven't tried a needle or tooth pick.

My EDC is a mini grip M390, it doesn't hang up at any point on the blade cutting phone book paper, will shave arm hair and of course push cut said paper. My last couple passed on the white sticks are as light as I can get them and still make contact. Perhaps that knocks the wire edge off?

At any rate I am satisfied with the way my knives cut. If I have a problem it is because I am on the shoulder and going back to the 30 degree setting and flatten out the primary bevel and finish with the 40 degree angles fixes the lack of sharpness I have come to expect.

Anybody having trouble with a Sharpmaker, keep reading and practicing. The system works.

 

[savasyn]

Thanks everyone! I really appreciate all the responses and will keep all that in mind as I practice this new-to-me art. Guess I'll keep the next phone book they drop off on our doorstep.

From the descriptions above, it does sound like the wire edge is the culprit in my case. With practice, I'm sure I'll get better at getting a true edge.

Thanks again!

 

[Ankerson]

Hello all,
I've recently taken a huge leap in my previously pathetic attempts to sharpen blades by picking up a Spyderco Sharpmaker. Thankfully now I am getting something between very usable and pretty impressive(for me, at least). As I'm still very new to all of this, I definitely have a LOT to learn, so I joined this forum

Quick question about the results I'm getting though. I find that with decent steels(I had been practicing on some $5 junk knives with very questionable blade materials), I can get a really impressive edge(for me at least) but that it doesn't last more than a few cuts. To be specific, my EDC is a Spyderco Ambitious with 8Cr13Mov(arguably the best steel I've attempted to sharpen so far) takes a razor sharp edge off the ultra fine stone and strop block but loses it after a few passes through cardboard. It's still quite usably sharp at that point, just not what it was minutes before. Is this to be expected with this steel against cardboard or am I most likely doing something wrong?

In the "am I doing it wrong" department, when I sharpened my Ambitious, I used the 40 degree angle per the instructions. I've since read that Spydercos come with a 30 degree edge from the factory so perhaps I should have used the 30 degree angle to sharpen for consistency. I just read through a couple of threads on micro bevels, and it sounds like I might have done that inadvertently to this knife. If that were the case, shouldn't I have better edge retention with the less acute angle? If I should have stuck with the 30 degree inclusive, is there a safe and simple way to get back to it at this point for someone of my very limited skill? I do have the diamond stones for the Sharpmaker in case those might be needed.

Hopefully that all makes sense. Perhaps this is all just a phase new sharpeners go through, especially with less tough steels like 8Cr13Mov. We get all excited when it works and want it to last, but perhaps that steel just can't maintain a razor. As I said before it's still quite sharp, just noticeably not what it is right off the stones.

Thanks in advance for any thoughts or advice!!

You are asking a lot for a low alloy steel cutting cardboard, very few steels can take that kind of wear and hold a razor edge for very long. If that's what you want then one of the high wear resistant, high alloy steels at high hardness would be needed.

Cardboard is and can be very hard on edges depending on what the cardboard is.

 

[me2]

What is your definition of razor sharp? Do you mean shaveing your face, arm, leg, catching hair above your skin on your arm, head, leg, or some other measure? Depending on how you define the term, I've had edges off the Sharpmaker that would still catch hair above my skin after cutting about 30 feet of cardboard. I've also had edges that would still shave a few hairs off the back of my hand after cutting over 100 feet of cardboard, again off the Sharpmaker. I've never been able to get an edge off the Sharpmaker I'd feel comfortable using to shave my face. Also, because of the very high pressures exerted by the triangle corners, the Sharpmaker can produce a very stubborn burr that can be difficult to detect, and will not be removed by a hand strop. Search here for user Jeff Clarke. He has a good deburring procedure that is effective for the Sharpmaker.

 

[Tunblor]

A great piece of advice I read somewhere for cutting cardboard:

Cardboard will make your knife blunt because it is very abrasive; for this reason, it can also make your knife very sharp. If the cutting resistance is getting a bit high, find a hard flat surface to lie a good strip (strop) of cardboard on, and then using very light pressure strop the knife 5 times each side, and then once each side until the knife is feeling sharp enough again (this would be especially helpful for you, if your knife is losing sharpness due to a wire-edge or burr).

I have found this incredibly useful, especially for the softer steels. This won't help however if your knife is chipping on dirt/concrete (like on the ground at the bottom of a cut) or on staples. Good luck!

 

[Gunsnknives]

All of the above advice, especially from Ankerson and Obsessed with Edges is good. I'm a simple man and the key points I will reiterate is that:
1) Cardboard can be very abrasive on a cutting edge. Losing it quickly is not surprising.
2) You may have a wire edge that is contributing to this. Try cross cutting against wood as suggested above to test/eliminate this.
3) Steel is a big factor. The Chinese steel you are using is fine, but not nearly the same wear resistance as some of the other steels available today (M390, S90V, ZDP189, M4, etc.). I'm not being a steel snob, but those steels were developed for high wear resistance. The upside to using your steel (and the downside of the high wear resistance steel) is the ease of sharpening. Generally, the higher wear resistant steels are more difficult to sharpen...generally...

Good luck with sharpening. I'm glad to hear you use a strop, because that made a bigger difference than I thought it would! I joined the forums to learn more too. I can sharpen WAY BETTER than before I joined the forums and have fun testing out new steels when I get a chance (and not just the uber steel...all steels!).

 

[boki_zca]

I have 2 knives that cut cardboard like crazy, one is Spyderco Moran, and other one is Bark River bowie.They both have convex edge and it helps a lot!