Best blade/edge angle for Tatami cutting

Jens Schuetz

Jens Schuetz

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Jun 24, 2013
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Our little HEMA organization has decided that to rank up we need to do traditional medieval ;-) tatami cutting with our European long swords. Diagonally up and down on both sides plus one cut on each side with a step. We get two mats to try that. I'll probably get my own stand own matts which I'll soak myself to increase the odds.
But getting more comfortable with grinding implements and having a cheap beater longsword (Coldsteel Italian) I'd also like to optimize the edge and maybe even the bevel. Both edges are identical as of now but I could make one of them a bit thinner for example.
What angles do you suggest.
Thank you for your help with this.
:-)
 
Get thee to youtube

There are any number of sharpening tutorials. This video is more or less "approved" by the HEMA crowd.

Cheers

GC

[video=youtube;dndjr3YXsLA]https://www.youtube.com/watch?v=dndjr3YXsLA[/video]
 
Cutting Tatami With Blunt Sword , John Clements ARMA
[video=youtube;ZR9k23U-P10]https://www.youtube.com/watch?v=ZR9k23U-P10[/video]
 
gadunz said:
Cutting Tatami With Blunt Sword , John Clements ARMA
[video=youtube;ZR9k23U-P10]https://www.youtube.com/watch?v=ZR9k23U-P10[/video]
Click to expand...
Thank you. What does that mean for me? Do I need a blunt sword or become John Clements? ;-)
Even John Clements will cut better with the best angle and which one that is would be interesting to know.
 
horseclover said:
Get thee to youtube

There are any number of sharpening tutorials. This video is more or less "approved" by the HEMA crowd.

Cheers

GC

[video=youtube;dndjr3YXsLA]https://www.youtube.com/watch?v=dndjr3YXsLA[/video]
Click to expand...
Thank you. Great pointers on the how. I just need the angle optimal for tatamis.
I'll probably just measure my katana edge and use that angle though they are probably thicker than they need to be to account for materials other than rice straw.
 
gadunz said:
Probly that extreme sword sharpness is secondary to speed & technique, when cutting tatami, & by extension, armoured body parts.
Stab to kill, cut to wound.
Click to expand...
From what I've seen last Sunday certain edges are worlds apart in that specific task but even the bad ones can be made to work by the better trained guys but also only on the easy cuts like the one in your video.
 
IMO, edge the sword as it was meant to be edged for it's intended purpose, then find what you need to do to cut with it.
Mike's sharpening video is pretty good-if you can find video of his students cutting those are good too.
I just feel like if the tool's geometry is dedicated to cutting tatami, then it's a recreational tool for cutting tatami, and not a sword. I've owned Japanese-style swords that were ground for tatami and would have suffered serious damage on contact with things a sword is supposed to cut.
 
J W Bensinger said:
IMO, edge the sword as it was meant to be edged for it's intended purpose, then find what you need to do to cut with it.
Mike's sharpening video is pretty good-if you can find video of his students cutting those are good too.
I just feel like if the tool's geometry is dedicated to cutting tatami, then it's a recreational tool for cutting tatami, and not a sword. I've owned Japanese-style swords that were ground for tatami and would have suffered serious damage on contact with things a sword is supposed to cut.
Click to expand...
Thank you J W B
I see where you are coming from and get why one would want to keep a sword a sword.

It's just that if I'm honest, cutting tests is all I'd be doing with it. The sword will never do what swords were meant to do.

I'm tempted to take one of the two bevels down to 30 incl. And then see how it compares to the edge on the other side.
 
Jens Schuetz said:
Thank you J W B
I see where you are coming from and get why one would want to keep a sword a sword.

It's just that if I'm honest, cutting tests is all I'd be doing with it. The sword will never do what swords were meant to do.

I'm tempted to take one of the two bevels down to 30 incl. And then see how it compares to the edge on the other side.
Click to expand...
All of my swords are a convex edge-that's what they would've been (except maybe for sabers sharpened at the armory or in the field-Horseclover could answer that one better than me)
I wouldn't put any kind of secondary/knife type beveled edge on any sword-it will cut like crap and be pretty hard to fix.
That Cold steel should sharpen up just drawfiling with a nice fresh smooth cut file-the CAS/Hanwei Tinker blades I've mounted and sharpened all worked that way, and I'd bet they're harder than the CS blades.
 
J W Bensinger said:
All of my swords are a convex edge-that's what they would've been (except maybe for sabers sharpened at the armory or in the field-Horseclover could answer that one better than me)
I wouldn't put any kind of secondary/knife type beveled edge on any sword-it will cut like crap and be pretty hard to fix.
That Cold steel should sharpen up just drawfiling with a nice fresh smooth cut file-the CAS/Hanwei Tinker blades I've mounted and sharpened all worked that way, and I'd bet they're harder than the CS blades.
Click to expand...




That's what I'm talkin' about. I'd try to convex the edge down to zero as best as I could, using a hand tool like a file, or fine sandpaper on a backer.
 
Thanks again everybody.
Convex is all I'm doing these days for my edges. Convexing the whole bevel sounds like fun. :-D
I just replaced the batteries in my angle measuring thingy and it turns out the longish knife, which had cut the best by far, has a bevel of 16.8 where it transfers to the flats and 17.5 at the very edge. So it's kind of convex and has no micro edge.
17.5 inclusive D2 seems crazy thin and I measured it a few times to be sure. What do you think?
 
If you finish your edge on a brown ceramic-either a gatco or a spyderfile-you'll get some very nice bite that will help on tatami/cloth/etc as well (and without creating drag)
This is the finish geometry on the Wu Jian I made from a cut down Cas/Hanwei longsword blade
 
I measured a few other knives and they all have similar bevels. So it wasn't that thin after all. I guess not having a primary edge but going right to the apex made it such a good cutter though I'm scared of testing it's edge stability.

J W Bensinger said:
If you finish your edge on a brown ceramic-either a gatco or a spyderfile-you'll get some very nice bite that will help on tatami/cloth/etc as well (and without creating drag)
This is the finish geometry on the Wu Jian I made from a cut down Cas/Hanwei longsword.
Click to expand...
Thank you JWB.
The Wu Jian looks slicey.
I'll try to get a more toothy edge. What grid does the brown ceramic equal?
 
I have no idea what grit it is-i've heard them refer to it as "medium". I think the rounded shape of the spyderfile and the gatco's has something to do with it as well-the edge will still shave hair but is very grabby.
 
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