sharpening for cutting water bottles, hanging ropes, tatamis

M

MichaelMyers

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Dec 10, 2015
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For best results cutting demos of water bottles, ropes and tatamis what works best? Highly polished, coarse toothy edges or middle of the road? What's grits to use? What about fully serrated edges?
 
What about the blade in question, it's geometry, steel type, and sharpening ability of the user?
 
Good technique by the person attempting the cut is just as important, if not more important, than the edge of the tool used to cut.
 
As high as you want, competition cutters are all about push cuts.

I figure I should add that you should experiment with bevel angles, straight bevels vs. convex and level of polish. Your steel might go under 20 DPS without damage etc. Best is to slowly reduce angle until you have edge failure and then slightly thicken the edge, your accuracy will have a significant effect.
 
Skimo said:
As high as you want, competition cutters are all about push cuts.

I figure I should add that you should experiment with bevel angles, straight bevels vs. convex and level of polish. Your steel might go under 20 DPS without damage etc. Best is to slowly reduce angle until you have edge failure and then slightly thicken the edge, your accuracy will have a significant effect.
Click to expand...

So I should put on a mirror polish for best results?
 
Yep. Your sharpening skill and form will be more important than having a polished edge bevel.
 
My skill isn't remarkable but passable I guess. I have a lansky and a cheap india stone. Can get a shaving, edge on both. My main cutting knife now has a lansky 280 grit edge at 20 deg. It will pop hair, push cut receipt paper and slice newsprint and soft tissue paper. But won't push cut newsprint. Should I go higher polish?
 
Traditionally speaking, katanas are used with highly polished edges and a convex edge. I personally think a decent thin machete would trivialize it though. Wouldn't be that great long-term, but if you're just doing a few cuts, I'd get one and stick a 25 degree polished convex edge on it.

I personally think something as thick as a katana would be more suited for lopping off limbs(as it was originally meant to do) with bones and everything, but after trying to chop down a papaya tree with my ESEE Junglas, it became pretty apparent that a cheap $20 machete would have done the job much easier even if it took a little more damage, simply because the thinner blade would go through with much less resistance.
 
MichaelMyers said:
My skill isn't remarkable but passable I guess. I have a lansky and a cheap india stone. Can get a shaving, edge on both. My main cutting knife now has a lansky 280 grit edge at 20 deg. It will pop hair, push cut receipt paper and slice newsprint and soft tissue paper. But won't push cut newsprint. Should I go higher polish?
Click to expand...

If you're interested more in push-cutting, a narrower edge profile would do that better. Assuming your '20 deg.' edge means 'per side' (40° inclusive), you'd likely find push-cutting easier at 30° inclusive or less (15° per side or less). More polish might help a little bit, but ONLY if the apex of the edge remains as crisp and thin as possible (it's easy to round off and degrade it by overpolishing). Thinner edge geometry will always make the bigger difference, and even at coarser finish if done well.


David
 
What edge to apply? The one you are most comfortable with applying.

The real question though is,

Is your cutting technique good enough for the knife you are using and edge you have applied?

A Katana is not always very sharp if it's a used weapon and the owner practices often then it's probably not much sharper than the average EDC. Blade geometry and practicing cutting technique can mean more than having the sharpest edge.
 
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I saw a special recently but cannot recall the station etc. To illustrate in part Jason's statement above, a gentleman whacked through a rolled tatami with a fairly dull viking-pattern long sword.

For "trick" cutting I'd imagine a mid to low 20s inclusive and a polished edge with thin stock behind the edge. After that, practice.
 
HeavyHanded said:
I saw a special recently but cannot recall the station etc. To illustrate in part Jason's statement above, a gentleman whacked through a rolled tatami with a fairly dull viking-pattern long sword.

For "trick" cutting I'd imagine a mid to low 20s inclusive and a polished edge with thin stock behind the edge. After that, practice.
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:) pbs.org/wgbh/nova/ancient/secrets-viking-sword
You can also watch on youtube
 
HeavyHanded said:
I saw a special recently but cannot recall the station etc. To illustrate in part Jason's statement above, a gentleman whacked through a rolled tatami with a fairly dull viking-pattern long sword.

For "trick" cutting I'd imagine a mid to low 20s inclusive and a polished edge with thin stock behind the edge. After that, practice.
Click to expand...

I watched it on youtube. Another one cutting bamboo but same guy Quite amazing I must say considering the sword was really blunt.

Anyway I have 20 deg per side 40 inclusive bevels now. I want to test with it first before going to 15 deg. Not into competition just sharpening my own cutting skills. Knife is only basic O1 tool steel not supersteel so I don't want to go lower than 20 deg and roll the edge on chopping.
 
MichaelMyers said:
I watched it on youtube. Another one cutting bamboo but same guy Quite amazing I must say considering the sword was really blunt.

Anyway I have 20 deg per side 40 inclusive bevels now. I want to test with it first before going to 15 deg. Not into competition just sharpening my own cutting skills. Knife is only basic O1 tool steel not supersteel so I don't want to go lower than 20 deg and roll the edge on chopping.
Click to expand...

Unless the edge is damaged, or you are cutting really knotty wood with small size pin knots, you shouldn't have to worry. I've cut down the angles on some machetes to 15 degrees in 1055 carbon steel that was about 55 HRc (it was easily filed). No damage unless I cut into something like that or overheat the edge while sharpening.
 
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