My fault: M4 blade @ 64Rc breaks

IGotStabbed said:
I think they faulted when they put a big ass hole in the blade!
Click to expand...

That is funny, since the toughest production knife I have seen stand up to abuse is a Spyderco Manix 2. It help up after all kinds of abuse. Gee, I wonder what Sal was thinking when he designed it with that useless hole? :rolleyes:
 
if you look at a spyderco blade geo, the hole doesn't take NEARLY as much out of the blade as that bm's did...if that makes sense
 
shelbysguns said:
That is funny, since the toughest production knife I have seen stand up to abuse is a Spyderco Manix 2. It help up after all kinds of abuse. Gee, I wonder what Sal was thinking when he designed it with that useless hole? :rolleyes:
Click to expand...
You've never seen an XL Espada, or even a ZT300 series. Both will handle more abuse in every way. There's videos of both taking more abuse than any Manix 2 has.
:rolleyes: :rolleyes: :rolleyes:
 
Call Benchmade and ask if they still have any spare blades left. If they do you can send it in and they will replace the blade for $35.
 
Something went wrong during the HT/temper for that to happen under 20 lbs of pressure.
 
I dinged up a blade on my EDC and it was bugging me. Benchmade put a new blade on it for $25 about 4 months ago. You just call them and then send it in. About 3 weeks later and you've got your knife back again.

Benchmade keeps a large inventory of parts including spare blades. If it's worth your time I'd send it in. They fixed me up and did maintenance and adjusting, sharpening on mine - came back like brand new. :)
 
Ya definately give BM a call. If they don't have any M4 blades (which they probably don't) they may be able to slap a regular production blade in there. worth a try...
 
cziv said:
I dinged up a blade on my EDC and it was bugging me. Benchmade put a new blade on it for $25 about 4 months ago. You just call them and then send it in. About 3 weeks later and you've got your knife back again.

Benchmade keeps a large inventory of parts including spare blades. If it's worth your time I'd send it in. They fixed me up and did maintenance and adjusting, sharpening on mine - came back like brand new. :)
Click to expand...
Yep, they sure do! It's $25 for uncoated blade and $35 for coated.
 
Ouch!
A bad heat treat and of course the opening hole is the origin of this snap.
64HRC IMO are really not necessary to have a great cutter. Also because it's a pig to resharpen.

Sorry for your valuable knife indeed!
 
Whenever I look at this model I'm surprised at how much space the hole takes. It's about 50% of the whole blade width!

Spyderco takes into account sometimes of the loss of material due to the hole. That is why they make up for it by making it wider or ensuring there is enough material left over where the hole is. At least it has been like that for my blades (Ti ATR, Manix 2, endura and etc). However this small blade has a humongous hole in relation to it's size and shape. I never liked it myself.

I think I remember seeing a picture of a Endura copy by Sog that decided to disconnect the material at the top of the hole (thumb rest area) in order to pass off as original design. Bad idea...
 
Not quite half the blade width; across the width, the hole is 10mm, and the blade from spine to cutting edge (where the hole measures 10mm) is 27mm
 
64HRC IMO are really not necessary to have a great cutter. Also because it's a pig to resharpen.
Click to expand...

Mostho, CPM M4 lives and excels at this hardness. I'd rather sharpen at this hardness than at RC 58-59.

That's what diamonds are for in any event.

Joe
 
Sucks about the knife :( Discontinued too!

I'd check out the HRc again. I've done that to a Gayle Bradley (supposedly 64 Rc as well) with no sign of failure. And the GB is a thinner grind.
 
The RC will tell how deep or shallow a diamond test point sunk in the steel, but it will not tell you if the carbides are evenly dispersed through the martensite or if they're all glooped in the grain boundaries or forming carbide stringers. Lots of stuff if won't tell you.

Very sorry for your knife loss, Twindog. If it's not too late, would you consider a Spyderco Gayle Bradley folder? As far as high-hardness M4 hollow-ground folders with sculpted carbon-fiber scales and meticulously comfortable fit and finish go, it's very nice.
 
I will consider the Gayle Bradley, but I'm going to wait to see how the Military in M4 comes out. I'm on that list. I think Spyderco does their M4 harder, and the blade will come with a thinner grind.

Benchmade was pretty nice. They said send it in and they'd put in a new blade for $35 (coated non-stainless). I don't know if they have M4, but anything is better than my current situation: a quarter-inch long blade with a safety tip. A little lacking for self defense.

This was the 806-901, which I really loved, other than its average cutting ability.


The hole in the blade is clearly a weak point, but normally with a folder you're not going to do anything that would break the steel. It takes lateral force, which the blade is not often going to see, unless your prying hard. And this is a pointy blade, so if you're prying I'd guess the tip would break first.

The hole has a very thin top rim. I don't know where the break started and I'm no expert. But I'm wondering if the rim broke first, creating a twisting downward torque that shattered the lower blade. That lower break is really the key. There are three pieces, and the middle one has break surfaces following multiple planes, including convex/concave planes. This blade shattered like glass.

If the rim broke first, the blade would have twisted and been exposed to force vectors from multiple directions. To me that explains it, but honestly, I don't really know.
 
bad for you. seems obvious that the heat treat was far from optimal. iirc HRC is just the goal and there are several ways to get there, the guy who did that for you probably didn't chose the best one.

btw how did he re heat treat the blade ? i assume that for finished and sharpened blade you need a very expensive setup with salt bath if you don't want to burn the edge? or make the edge flat (rounded) until a certan thickness is reached ?
 
I don't know how the reheat was done, but it was done by a skilled, highly respected knifemaker. Something could have gone wrong with the heat treat, but I'd guess it was done correctly. I have no complaints.

Broos made the point that the break has the signature of a heavy-loading failure, which it wasn't. But it was extremely brittle. Thombrogan also makes a good point that problems in the steel structure could also be implicated.

I also think it matters if the break started at the top or at the bottom. I'm thinking the top. If I could break the whole blade with just my hands, think of how easy it would be to break that thin rim at the top of the hole. The break at the top has the signature of a low load. The bottom part of the break has the high-load signature. But if the top of the blade broke first under low load, the blade would have been torqued -- moving in two directions -- perhaps making the lower break more complex and able to mimic the high-load break signature.

Still, this blade was very brittle. I see people put blade in vices and bend them with cheater bars to see how far they'll go before they'll no longer return to their original shape. This knife may have bent a bit at the pivot, but I didn't notice any blade bending. I can't imagine bending this blade at all without it breaking.
 
A_Blade_Afficionado said:
You've never seen an XL Espada, or even a ZT300 series. Both will handle more abuse in every way. There's videos of both taking more abuse than any Manix 2 has.
Click to expand...

I said that I had seen. Yess I think anything with a triad lock will win. I'm saying that a hole doesn't make a knife into a fragile spinster. Also the M2 is cheaper than either choice, am I right? Sorry, didn't mean to upset anyone. :o
 
You must log in or register to reply here.
Back
Top