Polished Blade Won't Cut Nylon Climbing Rope

ncrockclimb

ncrockclimb

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I have a 1/8" convex O1 fixed blade that I have stropped to a polished edge. It has a rather obtuse edge bevel of between 25 to 30dps. I can shave hairs off my forearm easily and it passes the "fingernail test." However, I can barely slice through a loop of rope. If I cut into it at an angle and sort of carve, I can cut it. If I lay the rope on the table, I can push cut it easily. Other similar knives I own that have a somewhat more acute bevel can slice through the rope much more easily.

So, sages of BladeForums, what do you think? Is it the obtuse edge bevel, the mirror edge, a combination of the two or something totally different that is causing my "sharp" knife to perform poorly when cutting rope?

Thanks for sharing your thoughts and experience.
 
Nylon rope needs to be "sawn." Polished edges don't cut it well at all.
 
It's the combination, but more the polish than the thickness I think. I'd bet a serrated edge would eat that rope for lunch. A hawkbill would do even better (particularly a serrated one).

If you want to use this blade on this rope, I would start by sharpening the blade with a very coarse stone, carefully deburring the edge and trying it out on the rope. The worst thing that can happen is that doesn't work any better and you'll have to re-polish the edge. But I suspect that a coarse finish, between 100 and 320 grit is going to work WAY better. I'd start at 100 myself; mostly because I have a 100 micron belt for my WSKO that has proven to make edges that really work on rough material.

I'll bet someone else here has experience with this type of rope and might have something more learned to say.

I'll be curious to hear your results no matter what path you decide to take.

Brian.
 
Thanks for the replies. Like a lot folks here, I use my blades for regular EDC stuff and camping chores. Cutting nylon climbing rope is not a "must have" attribute for my knife, but I was shocked that my uber-sharp scalpel (with a very obtuse edge) could not slice climbing rope as well as my dull beater knife.

bgentry, what do you mean by "carefully deburring" after finishing with the coarse stone? Would you just use light strokes on the coarse stone or would you make a few passes on a strop? Would stropping immediately after a coarse stone defeat the purpose?

Again, thanks for your input. I am a noob when it comes to knives and sharpening, and this sub forum has been invaluable for helping me to learn how to take care of my blades.
 
Carefully deburring means paying attention during the deburring process to make sure you've got it all removed. Depending on the steel and how you sharpened it, you might have to do different things. I normally pull the blade through cork to strip off any big burr pieces. Then, like you said, I do light back and forth strokes to try to remove any burr pieces from each side. Sometimes this isn't enough though, as the burr (or pieces of it) can flip side to side.

I've found that with a lot of blades, you need to be a little more aggressive. One good technique is to raise the sharpening angle up significantly; as much as 5 to 8 degrees. Then do *one* stroke, lightly, at that higher angle. Then do alternating back and forth strokes to even it back out.

Stropping is good for burr removal also. Stropping will also polish the "teeth" created by the coarse stone. This can actually be a REALLY nice edge to cut with. It's similar to a serrated blade with a very polished edge. It has some fine edge properties, but it also has "bite" because of the teeth imparted by the coarse stone. If you keep the stropping to a minimum, you won't get hardly and polish at all. Like 5 strokes per side. It might be interesting to test before and after stropping to see if you notice a difference or not. I'd suggest testing on both rope and paper both times. That way you can observe both types of cutting action.

Brian.
 
Morning all. How goes the nylon cut? I know paramedics use serrated blades to quickly cut through seat belts and such. Bob Dozier's edges are very aggressive, meaning saw like kind of. It will cut most things real fast and last. I read a great article about choosing the kind of edge for the material your'e going to cut, there's no one size fits all which is kind of cool. Ankerson, our edge testing guru, puts a 400 grit edge on the blades he tests on rope I think. I test my edges to see if they cut toilet paper with little down pressure. A polished edge will to but you need more pressure. For the stuff I cut most this thinking works for me. Happy sharpening.
 
Morning all. How goes the nylon cut? I know paramedics use serrated blades to quickly cut through seat belts and such. Bob Dozier's edges are very aggressive, meaning saw like kind of. It will cut most things real fast and last. I read a great article about choosing the kind of edge for the material your'e going to cut, there's no one size fits all which is kind of cool. Ankerson, our edge testing guru, puts a 400 grit edge on the blades he tests on rope I think. I test my edges to see if they cut toilet paper with little down pressure. A polished edge will to but you need more pressure. For the stuff I cut most this thinking works for me. Happy sharpening.
 
The best working edge I've come across (and the way I sharpen everything that's not a straight razor or a woodcarving tool) is to finish the edge with brown ceramic-either a gatco or a spyderco profile.(doesn't really matter what you use before that, as long as it's not too coarse. I use a hewlett 2 sideddiamond plate in the field) Shaves hair, slices paper-and if you lput the edge (gently!) on your thumbnail and draw it back will bite right in and stop.
For drawing cuts, sharpen heel to tip. For push cuts (broadheads etc) sharpen tip to heel.
The direction of even the finest sharpening scratches does make a difference.
 
bgentry said:
I've found that with a lot of blades, you need to be a little more aggressive. One good technique is to raise the sharpening angle up significantly; as much as 5 to 8 degrees. Then do *one* stroke, lightly, at that higher angle. Then do alternating back and forth strokes to even it back out.
Brian.
Click to expand...

Yesterday I sharpened a kitchen knife (VG10) on the coarse side of a Crystolon Stone until burr, tried to remove the burr as much as possible with single alternating edge leading strokes, then I raised the angle quite a bit for one stroke (one side) only and went back to single strokes at the original angle for a few more alternating strokes with very little pressure. Cleaned the apex up quite nicely. Obviously I would not do all that if I continued on finer stones but I wanted a aggressive coarse edge without stroppging.
 
J W Bensinger said:
The best working edge I've come across (and the way I sharpen everything that's not a straight razor or a woodcarving tool) is to finish the edge with brown ceramic-either a gatco or a spyderco profile.(doesn't really matter what you use before that, as long as it's not too coarse. I use a hewlett 2 sideddiamond plate in the field) Shaves hair, slices paper-and if you lput the edge (gently!) on your thumbnail and draw it back will bite right in and stop.
For drawing cuts, sharpen heel to tip. For push cuts (broadheads etc) sharpen tip to heel.
The direction of even the finest sharpening scratches does make a difference.
Click to expand...

Spot on! The op issues is why I say that you really don't see the benefits of a mirrored edge until you are to the sub 15 dps level, and even then edge thickness will play a factor. I finish all my edc edges at 600-1k grit on the Wicked Edge and it's a perfect combo
 
I don't care what edge you put on a knife, at 30 dps nothing cuts well.
 
Jason B. said:
I don't care what edge you put on a knife, at 30 dps nothing cuts well.
Click to expand...
That.^

"Other similar knives I own that have a somewhat more acute bevel can slice through the rope much more easily."
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That's the strongest clue as to what needs to be done.^

Whatever shaving or other 'biting' it's doing, it's likely a fine burr along the edge. Burrs will 'pass' shaving tests and fingernail tests, but won't do much else; especially with very thick edge geometry behind them.

Taking the edge down to 30° inclusive (15° per side) or lower, or at least sub-40° inclusive, will make a big difference, regardless of which finish you prefer. The apex must be crisp, at any finish, for cutting stuff like nylon rope. At 25° inclusive or lower, the edge finish becomes almost moot and purely a matter of preference, as the edge geometry is what's working for you (as it always should).


David
 
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Yeah 30 dps is blunt!
Anyways, polished edges are not for rookies (not saying you are), but my polished edges have no issue with nylon hemp or regular rope.
 
HwangJino said:
Yeah 30 dps is blunt!
Anyways, polished edges are not for rookies (not saying you are), but my polished edges have no issue with nylon hemp or regular rope.
Click to expand...

Actually, I am pretty much a rookie that is working hard to figure out how to put better edges on my knives. I am not offended by your post at all and really appreciate your (and everyone else's) input.

I am going to thin the blade back to about 20 dps with my new KME and the 300 grit diamond hone, then give it a few strokes on the strop. I'll see how that changes the performance, and if I am not happy with it I'll go down to 15 dps...

Thanks again for all the feedback. I'll keep you posted!
 
HwangJino said:
Yeah 30 dps is blunt!
Anyways, polished edges are not for rookies (not saying you are), but my polished edges have no issue with nylon hemp or regular rope.
Click to expand...
That's a good point. I have a super blue endura that has a highly polished edge and it has no problem with rope.
Even stropping, it's worth being aware of the direction of the stroke-though I think you're going to have to drop that angle to see good results.
Some steels like different edge types, in my experience-also depending on the hardness of the blade.
I've had hard tempered O-1 and 1095 that would not take a "bitey" edge to my standards-and I've had other knives that a polished edge just didn't get the most out of the knife.
The old Japanese sword polishers did the same thing (though not for sharpness but rather to bring up the best window into the steel).
 
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Hi, glad to see you're still at it. I see you just got a KME, is it the diamond version? Let me know your opinion about it. Once you get the dps down and a toothy edge, hold on Luke you'll have a light saber. Thanks for your straight up honesty, none of us know it all, we all are learning every day. Happy trails
 
J W Bensinger said:
I've had hard tempered O-1 and 1095 that would not take a "bitey" edge to my standards-and I've had other knives that a polished edge just didn't get the most out of the knife.
The old Japanese sword polishers did the same thing (though not for sharpness but rather to bring up the best window into the steel).
Click to expand...

"Window into the steel"... Do you mean how it looks? Something else? I think the sword polishers were/are pretty incredible.

Brian.
 
ncrockclimb said:
Actually, I am pretty much a rookie that is working hard to figure out how to put better edges on my knives. I am not offended by your post at all and really appreciate your (and everyone else's) input.

I am going to thin the blade back to about 20 dps with my new KME and the 300 grit diamond hone, then give it a few strokes on the strop. I'll see how that changes the performance, and if I am not happy with it I'll go down to 15 dps...

Thanks again for all the feedback. I'll keep you posted!
Click to expand...

Yeah the fun part is when you do it right and get that super edge, you want to show everyone haha.
 
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