How does CPM M4 fare as heavy-duty machete?

JayGoliath

JayGoliath

Joined
Mar 27, 2010
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Hi all,

I'm trying to get some feedback here before commissioning one to be made.
Read about the selection of CPM M4 steel as Bladesports and other competition choppers with great results.

Say an OAL of 16-20", blade thickness of 0.18 to 0.2" and about 1.5-2" wide, would a full hardening be a good HT method then?
Medium of chopping/slashing will be tropical low-growing vegetation with occasional de-limb branches of 5-6" in diameter.

I've also seen an option of 52100 instead of M4 due to the cost?

Appreciate your inputs.

Jay
 
I can't see a good reason to use M4 for a machete, but it should work just fine. Re-sharpening will not be a quick task.
I would think 52100 would be good, as would 5160. CPM-3V might be the best choice for a tough blade chopper.
 
M4 regularly wins cutting competitions, but those cuts are very controlled. M4 lacks ductility, so a wonky hit or incidental contact with a rock might lead to a chip, crack or break whereas a tough steel would simply dent or bend.

I made a machete from A2 once and it broke rather quickly. This makes me think that a tougher spring steel such as 5160 might be a better choice.
 
Thank you for the advice,buds.

Me2,

Why do you say so?

Nathan the Machinist said:
I made a machete from A2 once and it broke rather quickly. This makes me think that a tougher spring steel such as 5160 might be a better choice.
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This is refreshing Nathan! What did you hit? I would A2 is a lot tougher. Did the hardness go sky high for it to fail?
 
First is I think a large chopping blade shouldnt be made from a high speed steel. Nothing about the makeup or industrial use of high speed steel suggests it should be a large chopping knife. CPM M4 is touted as tough, but it is only tough when compared to other high alloy, high wear steels. Compared to steel in general, it is not tough enough to make a rough use blade.

Second is ease of repair. My rough use blades dont get dull. They get damaged from accidental impacts with the ground, rocks, dirty wood, knots, etc. I dont see a lot of value in high wear steels.

Third is cost. CPM M4 is expensive to buy, grind, harden, and finish.
 
CPM 3v would be a better choice. 52100, 5160, or S7 would be good choices if money is a factor. The super steels cost quite a bit more in terms of raw materials, belt wear, and time. Then again, if price is a big factor you could just buy a Scrap Yard 1311.
 
I'd vote 5160, but it's what I work with the most too. :) I've chopped plenty of brush in my time, and have nothing bad to say about 5160 in this application. Tough, holds an edge well, but re-sharpens easily when the time comes.

Edit to add: That's interesting to hear from you folks with more experience about the M4. I had a table at the Lone Star Knife Expo this past weekend, and the cutting competition blades there from what I heard (didn't get to see much of the competition) were all M4. I'm of the opinion that any time something becomes a competition (tractor pulls, stock car races, lumberjack competitions) it swiftly no longer represents what it started out as as things become specialized to fit the competition. For instance, the "racing axes" used in the lumberjack competitions, from what I've read, are very hard and very thin. I've seen them on T.V. knocking out dinner plate-sized chunks of wood as fast as they can go. However, it's in soft, knot-free wood. Take that same ax and go after a Comanche County blackjack oak, and you'll likely bust up the edge in short order. I had wondered if that was the case with the M4.

Kind of like how a NASCAR "stock" car is not what you want to drive your morning commute every day, and you don't plow the back forty with a tractor stuffed with an Allison V-12 with nitrous.
 
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M4 does great at choppers...I've made a few. But, man you're looking at one heck of an expensive and time consuming project....and there are better steel choices for what you wanna do. M4 is best for small-medium/large blades. You're getting extra wear resistance with M4 that I'm not sure you can take advantage of in a knife that huge....maybe if you were chopping vegetation only...only one way to see ;)

I love the alloy and it is so dynamic depending on hardness.
 
Storm Crow said:
I'd vote 5160, but it's what I work with the most too. :) I've chopped plenty of brush in my time, and have nothing bad to say about 5160 in this application. Tough, holds an edge well, but re-sharpens easily when the time comes.

Edit to add: That's interesting to hear from you folks with more experience about the M4. I had a table at the Lone Star Knife Expo this past weekend, and the cutting competition blades there from what I heard (didn't get to see much of the competition) were all M4. I'm of the opinion that any time something becomes a competition (tractor pulls, stock car races, lumberjack competitions) it swiftly no longer represents what it started out as as things become specialized to fit the competition. For instance, the "racing axes" used in the lumberjack competitions, from what I've read, are very hard and very thin. I've seen them on T.V. knocking out dinner plate-sized chunks of wood as fast as they can go. However, it's in soft, knot-free wood. Take that same ax and go after a Comanche County blackjack oak, and you'll likely bust up the edge in short order. I had wondered if that was the case with the M4.

Kind of like how a NASCAR "stock" car is not what you want to drive your morning commute every day, and you don't plow the back forty with a tractor stuffed with an Allison V-12 with nitrous.
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I love your analogies... very insightful. Not that I watch monster truck rallies or tractor pull contests... but I know they happen (somewhere... with someone watching... I guess). :)
 
The impression that I get is that M4 was chosen for competition cutters because it offered he best combination edge stability when very thin, edge retention and toughness. With that said, a couple of years ago, a Brit friend of mine Ian Aleen-Rawlinson, because the first European competitor in the World Cutting Championships at Blade. He placed 6th his first time out and used a knife made from O1 that was heat treated using a recipe devised with Kevin Cashen's help. Interestingly enough, I asked Kevin what reasonably priced carbon steels he would use for something like a "mid tech" run. he told me that he would probably use O1 for smaller "slicers" and 52100 heat austenized below the "saturation point" for larger choppers.
 
JayGoliath said:
Medium of chopping/slashing will be tropical low-growing vegetation with occasional de-limb branches of 5-6" in diameter.
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It may sound like heresy coming from me, but I wouldn't recommend a super-thin edge on a blade like that. It's going to get banged up pretty quickly. A basic convex or 40-degree-inclusive edge will tear up branches and vegetation nicely, and be robust as well. So if a super fine edge isn't necessary, that pretty much eliminates any reason to choose CPM-M4.

As far as I know (which admittedly isn't very far), what the other folks here are saying about M4 and comp cutters is true. It's chosen mainly for its edge retention; those guys need to chop 2x4's, golf balls and other tough targets and then make very precise cuts... all at high speed. That's just not the same kind of application as a machete or camp knife. We also need to keep in mind that competition knives are almost always a minimum of .250" at the spine, sometimes much thicker - that's a lot of steel to back up the extremely thin edges they use.

My first choice for a project like yours would be CPM-3V... not as much edge-retention as CPM-M4, but still pretty dang good at 58Rc. It has similar corrosion-resistance and much better toughness. Honestly, if cost is a concern, I'm confident 1084 would do just fine in a big blade like that. It's certainly tough, and holds an edge better than it usually gets credit for. You could also ask the maker to HT the edge good and hard, and draw back the spine to a spring temper.

JayGoliath said:
Say an OAL of 16-20", blade thickness of 0.18 to 0.2" and about 1.5-2" wide...
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In addition to steel selection, I have some concerns about the geometry you're describing. That's a big chunk of steel! Really more of a small sword than a machete, and personally I wouldn't want to work with something that heavy for very long.

I would think about coming down to .125 or maybe .185" max stock with a full, mild convex grind and a good deal of distal taper. I suspect that would still give excellent reach and leverage/power, without being so heavy and forward-balanced that it will want to pull your arm along with it at full swing. Most machetes are well under .125" at the spine, made of cheap steel with fairly poor HT, and honestly they do very well at the kinds of task you're describing.

Sorry for the long-winded rant; I have a client with a similar project in mind, so we've been hashing through all the same questions :)
 
For my bush swords, I might have a point along the spine that is near .25", but that is at the chopping sweet spot, and there are distal tapers both directions, so the overall weight is kept low. The blades also have a full flat bevel, forged and filed, which means it cuts well while keeping weight appropriate. Force is mass times acceleration, and in brush cutting, acceleration is the more important part of the equation. Some inertia is needed to bite well, but too much inertia means that you're fighting it to get enough acceleration to cut well.

Essentially, I agree with James Terrio. :)
 
Of course, if you want impact resistance greater than that of A2 and the edge retention of say S35VN or S30 V, you could go with CPM 4V, if it is on the market yet or Bohler-Udderholm Vanadis 4E, which appears to be quite similar. The charts that I have seen indicate the CPM M4 has toughness/impact resistance in line with A2, which is pretty tough for "normal' cast steel, but maybe 1.5 times times the abrasion resistance of say S35VN.
 
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Storm Crow said:
For my bush swords, I might have a point along the spine that is near .25", but that is at the chopping sweet spot, and there are distal tapers both directions, so the overall weight is kept low.
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Awesome post, thank you! If I understand you right, you are employing that sort of compound-grind to put the balance and best geometry exactly where you want it.
I understand the concept, and have used it with success on smaller knives (10" or less blades) , but I haven't made real a big'un yet.
 
Thank you for your valuable inputs and sharing! Looks like 3V is a winner.

I've looked into V4E but there's just too many steels to choose around.

James,

That's an eye-opener on the 1084 steel. I believe Browning Competition Cutter uses that as well.
 
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james terrio said:
Awesome post, thank you! If I understand you right, you are employing that sort of compound-grind to put the balance and best geometry exactly where you want it.
I understand the concept, and have used it with success on smaller knives (10" or less blades) , but I haven't made real a big'un yet.
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What is this "grind" of which you speak? I forge 'em in. :D Forging tapers kind of comes naturally to the process, especially if you are forging as closely as you can to your final product. Grinding takes more effort to get the same results. Of course, grinding has plenty of advantages over forging and vice versa. It's all balance.

Typically on my bush swords, the widest part of the blade is also the thickest. When I forge my preform, that area stays closest to the original bar stock, then I forge my bevel, which is a full flat bevel. At that thickest, widest part, or just back of it, is the chopping sweet spot. You can keep the overall weight pretty low like that while still making a powerful chopper. Don't know how it would match up in a competition blade, but I know how it does on mesquite and oak. :)

I know the main topic is alloy choice, but making blades is kind of a total package thing. Good alloy with bad geometry or bad heat treatment will not equal a good blade, and so forth.
 
JayGoliath said:
That's an eye-opener on the 1084 steel. I believe Browning Competition Cutter uses that as well.
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It's either 1084 or something very similar, depending on whom you ask. Great knife :thumbup:

Storm Crow said:
What is this "grind" of which you speak? I forge 'em in. :D Forging tapers kind of comes naturally to the process, especially if you are forging as closely as you can to your final product. Grinding takes more effort to get the same results. Of course, grinding has plenty of advantages over forging and vice versa. It's all balance.
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All true! The amount of labor and waste involved in the stock removal process is a big reason I don't do a lot of large blades.

Storm Crow said:
I know the main topic is alloy choice, but making blades is kind of a total package thing. Good alloy with bad geometry or bad heat treatment will not equal a good blade, and so forth.
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Also true :thumbup:
 
In the realm of Machetes flexibility and thin geometry reign supreme. I believe it is the "cheap" carbon steels, and spring steels that excel in this arena. I am not sure if 3v
would serve well in this area with the sub 1/8 inch blade thickness of machetes (I have just never seen it).


Machetes require a steel with lost of what I call "bounce", the ability to bend rapidly and spring back to form and I just don't know of 3V's flexibility, it is very impact resistant but I have not seen studies on its "springy-ness" at very thin geometries.


Not to mention the cost, machetes (even good ones) break all the time just due to the thin blades which by definition is more fragile, I'd feel better about breaking a "cheap" steel rather than probably $200.00+ of 3V or $300.00+ of M4.

My personal choices for Machete steel are 5160, 1075/1070, maybe 1084 depending on HT. Or even 1055, I have used many machetes in 1055 and they work great and are inexpensive.
 
I love M4, but not for this application. At proper hardness it holds a brilliant edge, but (especially for comp blades) it is a beautiful dance of compromises. If you are not breaking stuff, you are not pushing the edge of competition. M4 sort of typifies this in that chips and cracks can and do happen.

At the wrong hardness (softer) it may be less chippy, but you also loose a lot of what makes it great.

It's also fairly expensive.

Regarding sweet spot weighting...it's a great idea, but you can get by with less by using two weight points farther apart and let inertia work for you;) just my humble opinion.
 
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