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A good friend of mine has been bugging me to make him a machete.  We've got the design sketched out and I bought some 1/8" 6150 that I plan on using.  I have a couple of questions for those of you that have built these before.  Mainly, what do you find to be the best style of grind to use?  I'm leaning towards something in the range of a flat grind at 15 degrees on each side (give or take), down to a zero edge, but I'm not quite certain.  Secondly, what range of temper should I be looking at.  Given that it'll definitely see some hard use my thoughts are in the 500-550 range, but I've never done a blade quite like this and I'm worried that it might end up a touch too soft.  Thanks for any help!

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I've made a few and personally I use a flat grind; however, I wouldn't take it to a zero edge, especially if it's intended for heavy use. I usually flat grind the blade into a thin version of an appleseed grind as you might do on a sword edge, but I've also put a more scandi type grind on some, so that the impact is concentrated on a steeper edge for chopping and separation rather than cutting.  I also usually go thicker than 1/8", but that should work just fine and make it nice and light. As far as heat treating it I've never done anything too drastic to soften the blades and haven't had an issue yet, but if you want a bit more softness I'd maybe temper around the 450-475 range rather than 500-550, just my .02. I hope this helps out and I'd love to see pics when it's finished.

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Thanks @jacob beer.  I appreciate the input.  Glad to see that my thought process isn't too far off.  I didn't do a very good job of explaining the grind, but a scandi type grind is what I was thinking.  I believe a true scandi is in the 11-12 deg per side (22-24 deg included)  I was thinking of going 15 deg per side (30 deg included) to give it a bit deeper cutting ability and still have a good stout edge behind it.  I'm really happy you're not saying to temper it higher than 550 as that is about as high as the kitchen oven goes!  I'll start in the 450 range and test it out to see how well it holds up.  What are your thoughts on a differential heat treatment?  I've been considering either an edge quench or significantly drawing the temper back along the spine and upper half or so of the blade.  With something of this proportions I'm concerned about the blade snapping if it takes a glancing cut, or gets stuck and has to be forced back out of the wood.

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At 400F 6150 should be near 54 HRC, 450 should be closer to 52 HRC.  That is some pretty heavily tempered martensite.  I wouldn't worry too much about differential hardening with that, especially considering how tough 6150 is anyway.  You have about 3 seconds to beat the nose of the curve, but if you go a little slower you will get a little retained austenite, ferrite, and carbide.  The carbide isn't too bad of a thing, and your tempering will probably take care of the retained austenite (and more carbide formation), so you will likely end up with very little performance loss.  This may come in handy when trying to keep a machete sized piece of 1/8" steel hardened.  

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For reference, here are my two favorite machetes to use.  The shorter one is a U.S. Army-issue by Ontario Knife.  Steel is 1095, and it has zero flex.  It's just a flat bar a hair thinner than 1/8" with a deep hollow grind edge about 3/8" tall.  The longer one is by Tramontina of Brasil, 34" OAL.  It is much thinner, unknown steel, again just a flat bar, but with a short scandi edge about 1/4" tall, full spring temper and can bend double without taking a set. I suspect it's the equivalent of 15n20 or 8670.  The Ontario Knife one works best on woody brush and trees, the Tramontina is absolute death to grasses and soft herby stuff.  Not so hot on trees, though.  

 

m1.jpg

 

m2.jpg

 

m3.jpg

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Thanks Jerrod!  400 is definitely in range of the oven, hopefully the blade will fit.:D  It's good to know that I have some leeway with the hardening as well.  I've never done a blade this long before so it'll be an experiment to see how evenly I can get it up to temp in the forge.  I know 6150 calls for short soak as well which is already going to make things pretty interesting. 

 

Alan that thing is a monster!  My buddy originates from south of the border and has a ton of time swinging a machete under his belt.  He was extremely picky about the length and the profile.  His comes in somewhere between the two of yours.  I'll post a pic of the template once I get it cut out.

Edited by Alex Middleton
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I should note that my information is just my interpretation of the data in the ASM Heat Treater's Guide, not experience with this alloy.  The book also says nothing about a need to soak at temp.  

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I am really interested in seeing how this turns out, I've been thinking about making myself a machete for around the farm.  We have an ancient one with the handle being held together with duct tape, would be good practice to upgrade it.

 

Alex, I would love to see what you come up with when the time comes.

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Thanks Adam.  This one is on the docket for sometime in the next couple if months.  I'll make sure to post updates once o actually get started on it 

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  • 3 weeks later...

I was able to see some time aside to get his template transferred to the stock.20210602_164516.jpg

 

At .120" thick it's going to be a beast.  I'm think I'm going to cut it out and slap a temporary handle on it before going too far.  It'll give him a chance to swing it before I put too much work I into it.

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Decided to go for it and get it roughed out.

 

20210602_192317.jpg

 

Came out at exactly 2lbs.  Obviously it's quite forward heavy.   I don't think I would want to swing it for very long, but I'll let him try it out and see what he thinks.

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