Polished Blade Won't Cut Nylon Climbing Rope

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

Brian.
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Saw a documentary on katana making and a polisher spends about a year to polish a blade. He was scrubbing a stone the size of a rice grain on the blade for more than half that time he said.

they were/are obsessed with super polished edges and finishes.
 
The "window into the steel" is a fairly complex and amazing thing. When the sword is forged and heat treated you get different formations of the steel as it was going into its martensite phase along with the surrounding softer steel that has its own characteristics. Things like impurities in the steel and uneven distribution of elements will be brought out by the polishing along with the Hamon. Using an expensive set of Japanese natural stones and sword polishing tools the polisher reveals all these features of the steel creating a "window into the steel".

Truly amazing if you think about it.
 
nylon that is slack is pretty hard to cut, unless your edge really grabs it. Under tension, its a different story, which is why kernmantle ropes are the way they are. If the strands are aligned, then anything that cuts one can cut them all, the zig-zag prevents that to a degree. to add tension to the cut, you can cut on a diagonal, but that makes a mess. otherwise, just cut against something for a clean cut.
 
DPS == Degrees Per Side . When talking about an edge angle, you can say "25 degrees per side" or "50 degrees inclusive" and mean essentially the same thing. We mostly talk about edge angles in DPS around here for consistency.

Brian.
 
I agree with others you should try 15DPS and medium grit, that should make very good cutting edge for nylon or other synthetic ropes.

BTW this is to professional knife sharpeners, it occurred to me while reading you post, has anyone tried sharpening right side medium rough while left side fine mirror polish? How would it perform? Would it give us performance benefit of both types of edges in one blade, if used on say general purpose camp knife? This way maybe we don't need to decrease DPS and keep it @25-20DPS?

I use similar technique on my partially serrated blades. Fine mirror polish on straight portion and rough medium on serrations. But I have never tried it on left/right sides before!
 
Wolf7 said:
has anyone tried sharpening right side medium rough while left side fine mirror polish? How would it perform? Would it give us performance benefit of both types of edges in one blade, if used on say general purpose camp knife? This way maybe we don't need to decrease DPS and keep it @25-20DPS?
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Remember that most of the polishing effect is really just on the bevel and will have minimal effect on cutting - the only part that matters for sharpness is what happens at the apex. Using fine abrasive on one side, and coarse in the other will still leave you with coarse "teeth" where the larger abrasive cuts microscopic gouges out of the apex, so you will still get a coarse edge even though you spent the extra time polishing the other side.

I don't see any reason why you'd want to keep an edge at 20-25 dps unless youll be chopping through hardened bone or antler or the like. Then your edge refinement probably doesn't matter much anyway.
 
FlameCycle said:
Remember that most of the polishing effect is really just on the bevel and will have minimal effect on cutting - the only part that matters for sharpness is what happens at the apex. Using fine abrasive on one side, and coarse in the other will still leave you with coarse "teeth" where the larger abrasive cuts microscopic gouges out of the apex, so you will still get a coarse edge even though you spent the extra time polishing the other side.
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I have 2 identical chisel ground tantos, recently I re-sharpened one of them on my new WSKO which resulted in flat back side still has black coating while front side got mirror shine polished convex lens, no more black coating. Now when I cut same material ex: vegies carrots, tomatoes, cucumbers, potatoes I notice there is a big difference between these two identical blades. The blade without coating is now much better slicer partly because convex edge is better that flat V and partly because that black coating creates more friction than polished stainless steel.

So it isn't just apex of cutting edge but also sides of the blade that have effect on it's cutting capabilities. Smooth sides with no sharp angle edges makes it easier for blade to sink into material its trying to cut.

So going back to OP if he wants to get best overall performance out of his camp knife maybe smooth polishing one side and leaving other side rough coated will result in better cutter for both smooth synthetic and rough natural materials?

FlameCycle said:
I don't see any reason why you'd want to keep an edge at 20-25 dps unless youll be chopping through hardened bone or antler or the like. Then your edge refinement probably doesn't matter much anyway.
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Again, referring to OP if he wants his camp knife to cut synthetic rope and do all camp chores, for him it might be best to keep it @ average 20DPS.
Personally I would carry serrated re-curved folder with 15DPS for rope cutting, fine work and fixed camp knife with 20-25DPS for rough hard chopping etc.

I believe in using right tool for the right job!
 
Another option in this situation is to divide large blade into 1/2 or 1/3 and sharpen each portion 20/15 DPS or 25/20/15 DPS and apply different grit finish to each section. Supposedly, this will give you multi purpose blade, that is tuned for different materials. It's time consuming and can't be done efficiently by hand, but probably worthy it if you wish to carry only one knife with you.
 
25 - 30 dps is way to broad for any cutting tool. Thin it out to about 1/2 that and try again. While a polished edge mightn't be the ideal finish for that sort of rope, it should still cut easily enough, just dull faster than a rougher finish on the same steel. A thin grind and medium to coarse finish - 300 to 800 or so should blast right through that material.
 
Wolf7 said:
Another option in this situation is to divide large blade into 1/2 or 1/3 and sharpen each portion 20/15 DPS or 25/20/15 DPS and apply different grit finish to each section. Supposedly, this will give you multi purpose blade, that is tuned for different materials. It's time consuming and can't be done efficiently by hand, but probably worthy it if you wish to carry only one knife with you.
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That's not something I've ever heard or tried. What have been your results with this method?

Brian.
 
bgentry said:
That's not something I've ever heard or tried. What have been your results with this method?

Brian.
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Brian, I've attempted this on mid sized choppers - a large camp knife and a kukri. IMHO is not practical and virtually impossible to pull off cleanly. I initially came across it in the SAS survival handbook by Lofty Wiseman.
 
So... I got the KME and used the 140 diamond hones to re profile the blade to about 20 dps. I spend a lot of time developing a burr on both sides and getting the blade as sharp as I could with the 140. Then, I spent maybe 5 minutes with the 300 diamond hone, then about the same amount of time stropping with Flexcut Gold.

The resulting edge will slice through thin catalog paper with ease (Thanks Cabela's. I knew that stupid hard cover catalog you send me 2x a year was good for something!), easily shave hairs off my arm (I have a bald spot to prove it!) and cut through 10.5mm rock climbing rope like nobody's business. I am not sure how durable this edge will be, and it is not convex anymore. However, so far I am happy with the knife and the edge I put on it.

On a totally separate note, the KME is awesome. I am really happy with it so far.

Thanks for all the advice and helping me work through this!
 
HeavyHanded said:
Brian, I've attempted this on mid sized choppers - a large camp knife and a kukri. IMHO is not practical and virtually impossible to pull off cleanly. I initially came across it in the SAS survival handbook by Lofty Wiseman.
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To do it right you need to use sharpie to mark the blade 1/2 or 1/3 than use some kind of precision sharpener that has set angles.
Doing it by hand doesn't come out quite right!
Also, I have seen it done on blades with complex blade shape ex: re-curved regular or re-curved tanto blade, this way chopping/push belly has 20DPS while carving/pull scallop toward handle has 15DPS.

I recently bought complex "S" shape big knife/short sword and I'm trying to figure out now what optimal combination of angles to use to get best slashing and chopping out of it. I have to take into account 420 steel, blade thickness and shape. It gets complicated fast!
 
Thin out the blade first and then put 20dps edge on it.I finish my edges on spyderco brown ceramics mostly and they cut soft materials like crazy and also whittle hair.
 
And yet I have edges waay beyond 160,000 grit that drop through rope with just the weight of the blade..
 
Sadden said:
And yet I have edges waay beyond 160,000 grit that drop through rope with just the weight of the blade..
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Yup, I'd say that a properly formed and polished apex will work better by pushcutting a nylon rope. Coarser edges will tend to work better if used with a slicing or sawing motion.
 
singularity35 said:
Yup, I'd say that a properly formed and polished apex will work better by pushcutting a nylon rope. Coarser edges will tend to work better if used with a slicing or sawing motion.
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Coworkers are always amazed when I push cut the thick yellow zip ties that come wrapped around large boxes of chicken pork or beef.

I guess polished edges are only for the dedicated willing to give it a try and keep pushing themselves.
 
HwangJino said:
Coworkers are always amazed when I push cut the thick yellow zip ties that come wrapped around large boxes of chicken pork or beef.

I guess polished edges are only for the dedicated willing to give it a try and keep pushing themselves.
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Polished edges aren't for everyone. :)
 
bgentry said:
That's not something I've ever heard or tried. What have been your results with this method?

Brian.
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I did it on a BK-4 regrind-I ground the whole blade to a high convex and then did a little steeper convex final edge on the chopping section. That doesn't translate well to edge bevel angles, but it works nicely with convexed edges.
If the HT is right it seems kinda unnecessary so far, but it's easy enough to do on a convex.
 
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