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 Post subject: Putting a convex edge on a machete.
PostPosted: Fri Aug 03, 2012 8:40 pm 
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Location: Madison Wisconsin
Mark,
I need advice on 2 purchases.
I need a set of water stones i can use to sharpen japanese knives, Machetes (convex edge), And my katana (also convex edge).
The katana needs to be pretty and there fore i will probably go to 8000 or 1000 in polishing. The machetes dont need more than 1200ish stone.
Now i know that sharpening a gyuto or santoku requires a perfectly flat stone, but for a thick convex machete i (think) i actually want the stone to take a curve because i have to get quite a convex edge on the blade.
So can i just buy normal stones and use one side for my Knives and the other side for my machetes?
I was looking to start with your 5pc set, but i am unsure if i should be looking for really wide stones for the bigger blades. (im also not looking to spend more on stones than blades them selves are worth )
let me know what you think.



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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Fri Aug 03, 2012 8:41 pm 
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Most people that do covex edges will use a slack belt or they will use a piece of sand paper on a spongy surface like a mouse pad. I don't know people that use an intentionally dished stone but I can find out.

Do you mind if I post our correspondence on my new forum? I'll take off your last name. There are a number of experienced sharpeners who hang out there that should be able to tell you what they do.t will help others that are looking for recommendations. You're welcome to come over and chat with us. Here is the forum:
http://chefknivestogo.freeforums.org/index.php



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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Sat Aug 04, 2012 8:15 pm 
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ANONYMOUS <> I use the edge of my stones, the 90 degree created from top to side, to sharpen my tourne knives (curved blade). It is not a convex edge, but it is the same premise. Additionally, you can round the corners out with a flattening stone to sort of replicate the stones the sword polishers in Japan use.



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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Sat Aug 04, 2012 10:18 pm 
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A katana does not have a convex edge--the edge is shaped like a clamshell, hence the Japanese name, Hamaguri. It is a pair of flat bevels blended together on a muddy stone and sometimes a microbevel added.

The Machete is best sharpened on a slackbelt to set the edge, and then refined and kept up with by using wet/dry sandpaper with a soft backing, like a mouspad.

Your sharpening needs, in my opinion, will be best served by getting a hard 1k, like the Shapton Pro 1k or Ume 1k, a Suehiro Rika 5k, and a Harbor Freight 1x30 belt sander and some choice belts from TruGrit. About the same price as the 5pc set.



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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Sun Aug 05, 2012 5:39 am 
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ANONYMOUS <> Eamon's the professional sharpener here so he's got the clout. I'm just a Chef that has rounded some stones to sharpen some curved blades. Please don't somehow interpret my earlier text as claiming to know how to sharpen convex edges. I had offered an idea, a method that could work, I reckon, but again... in theory, not from practice.

It just sort of seemed like if you got a thick brick stone and rounded it out with a flattening stone, you could rock out a convex edge... in theory I guess.




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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Sun Aug 05, 2012 1:33 pm 
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Well if you have an authentic katana that is a quality piece, you really need to consider natural stones and if it is of quality, a professional sword polisher's skills are required. If you are simply using a lesser quality katana for cutting mats and so forth without concern for finish, that is another matter entirely. The finish from most synthetics wont bring out the aesthetic qualities of a sword and will significantly devalue the sword. You are better off not polishing at all than using synthetics.

You can certainly make a convex edge with a flat stone surface, so no special stones are required. This is a matter of technique, not stone profile. In fact sword polishers - who I sell stones to - purposely shape their stones as a CONVEX surface, not a concave surface. This is done for reasons not at all related to the edge of the sword having a convex surface. Consider including a very coarse stone (64 grit) or belt grinder for the machete, which will frequently get significant edge damage. For Japanese knives, well there's lots of stone choices and you'll hear lots of opinions including mine.

---
Ken



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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Sun Aug 05, 2012 1:42 pm 
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The two stones demonstrated in the video are a natural stone Ohmura for the coarse rust removal and initial shaping and at the other end of the process, some uchigumori fingerstones FWIW.



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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Mon Aug 06, 2012 4:01 pm 

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I used the sandpaper technique on the machete after reading the initial recommendations and it worked really well (super sharp), so we can forget about them.
I think I am going to use the same technique on the katana. I have this exact sword http://sbg-sword-store.sword-buyers-gui ... akami.html. It's not a cheep stainless wall hanger, but its nothing i'm worried about scratching up too much. I accidentally hit a hidden CMU (cinder brick) while I was slicing some tall brush in the back yard, so the blade will never quite be right. I would have to take a lot of steel off to get rid of the ding. I was considering polishing it up and displaying it, but that is probably more time and effort than its worth.

I think I will just focus on buying a stone/strop set to sharpen the new Maruyoshi HD-5 Santoku I just ordered. I plan on getting an addict2 next and adding to the collection as fund/needs allow.


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 Post subject: Re: Putting a convex edge on a machete.
PostPosted: Mon Aug 06, 2012 4:27 pm 
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Ah, the Cheness! I had a Kaze and sold it and got one of the SBG custom Wakizashi's in T10 diff. HT'd and it actually shows a Hamon line! I would just use sandpaper and a cork block or something to polish up the side of the blades if you wanted to display it. By the time you get the chip out, you will have lost some of the width of the blade and the edge will be much thicker and you would need to reshape pretty much the whole blade. Something I would be concerned about with the chip is that it may have cracked where you can't see it and the whole blade may be weakened structurally. If you tap it on a hard object, or with say a metal pipe, does it ring and vibrate or just kinda thud or clunk? There may be some ways you can listen for a crack online, but I wouldn't do much cutting with that blade anymore until it gets checked out!! Polishing with the stones is a bit of a pain and expensive; not worth it IMHO unless you really know what you are doing!!

I would go up to say 1000 grit sandpaper and do an acid etch to see if there is any sort of temper line. Even though it's through hardened, some of the Cheness blades show very faint hamons.

That way you can get the Addict 2 sooner :)


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