I'm thinking of buying a Benchmade 581 Barrage because of the M390 steel. The specified hardness for this model is 60-62 which is a very wide range. If the actual hardness is 61 or better, I'd pull the trigger as this would be ideal for M390. Can anyone tell me the actual hardness for the 581 Barrage blade?

Thanks!

Welcome to the forum. I wouldn't get too concerned about exact hardness numbers. The difference between 60-61-62 Rockwell C hardness is academic. Hardness is only one measurement to look at when evaluating a blade material.
I have a 581BK Barrage and I can tell you it is the finest knife I own (and I have over 30 quality choices). The M390 Benchmade uses is a high quality manufactured and heat treated material. Pick it up and tap it on a hard surface; you will sense the hardness. Use it frequently to cut just about anything and it will maintain an edge better than 1095, BG-42, 440C or S30V. Although S30V comes close in servicability. My only advice is to be very careful with the "Axis Assist", it has a strong deployment and takes some practice to handle it safely. I was bitten by mine the first day, luckily I had bandages readily available.
All in all, the 581 is an exceptional knife.

Jim Lucier

Following what Jim said, there are a lot of parameters to track from batch to batch, and from knife to knife. Regardless of whether it's machines or humans doing the work, you'll always have variations.

If they wanted 61+ Rockwells and could guarantee it, they wouldn't start the range at 60. Where do you get the impression that 60-62 is a very wide range? I'm wondering what other makers can guarantee a more specific blade hardness, and which among them can be trusted to actually be so accurate.

Ultimately, remember that products are more than spec sheets. If you like the design and feel of the 581, I'm sure the knife will perform admirably for you.

you should google Phil Wilson and M390 . I would be pleased to know my 581 was 60+ . We are talking production knives. He explains it pretty well on the Spyderco forum.

"Phil Wilson" from http://spydercoinc.net/forums/...683535&postcount=106

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All these high vanadium, high chrome high alloy steels like M390 and CPM S110V and CPM 90V are somewhat sluggish in the heat treat. It takes a high temperature, a very quick initial quench and a long LN2 cryo to get at least a value of RC 62 as quenched. Tempering at 375 is necessary to get some stress relief and ductility. 375 will drop the hardness at least one point so a hardness of 61 is pretty much on the high end of what can be expected with the best of processes and equipment. Consider also a plus or minus one point precision on hardness testing and it turns out that 59/60 is a very good target to shoot for. I have pushed M390 to 63 by using the high end temper where there is a little hardness bump due to secondary carbide precipitation. This is however a kind of hit or miss deal since the error range on typical thermocouples is about 3% at temperature. This means there could be a temperature control error of 30 degress and that is enough to miss the hardness bump. Steel companies caution that at this high end temper some corrosion resistance and toughness will be lost. So the low end temper is the most forgiving overall and the most conservative target.

This is a lot of tech stuff but wanted to put into perspective what it is like to heat treat these steels. Keep in mind I do one blade at a time, can check the hardness throughout the process and make adjustments if needed. If Spyderco were to do it like I do the Mules would probably cost $300 each. Yes edge holding is better at higher hardness but the tradeoff is ductility. Again I have the luxury of knowing who gets my knives and I can emphasize that there are some things you can’t do with a very thin hard edge. M390 is very fine grained and tough but there are practical limits to how far you can push blades that are optimized for specific use. Edge holding on M390 at 60 is up there with the best and there has been some work done by Bohler-Uddenholm using the CATRA testing to show this. I think that maybe BUC will also tweak M390 a bit to make it pop more in heat treat. After all they are learning some as well –yes they are interested in our feedback- and this steel was developed initially for a different purpose than knife blades.

Emphasis is mine.

In short, seems to agree with what's been posted:

1) There are always variations, in both production and testing
2) You can't do better than guarantee a 1-2 point range heat treating by hand
3) Even if BM could do higher HRCs, it would likely choose not to due to the tradeoffs
4) ~60 is a reasonable target for a general purpose blade
5) The 581 is not a $400+ custom*

* Spyderco mules are treated and sharpened blanks. I'm adding $100+ to Phil's figure since 581 has an AO folding mechanism and finished handles with scales and bolsters.

This message has been edited. Last edited by: kirbysdl,

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Reply

Thanks for the input guys. It’s my understanding that the Rockwell hardness scale is logarithmic, suggesting that relatively small changes in the HRC values equate to large differences in hardness. I’ve heard that most high-end custom knife makers closely control their heat treatment making any given steel harder than typical production knifes with the same steel. With that in mind, I figure M390 at a hardness of 62 could make for a really good production knife; whereas, a hardness of 60 might only be a mediocre implementation of the steel. Granted, M390 is a great third generation steel and would probably outperform most other steels even at 60.

All of my recent knife purchases have been Spyderco knives. From what I’ve read on-line, my impression is that they do a better-than-average job of heat treatment and QC in general. I haven’t been disappointed with any of their knives I’ve bought. There’s currently a limited edition Spyderco Paramilitary 2 available for pre-order in M390, but it’s got Smurf blue G10 scales. Smurf blue isn’t a bad color: I just have a hard time seeing it on my EDC. Thinking I might broaden my horizons, I was looking for another knife in M390 done with the same attention to detail that I’ve seen in the Spydercos. The 581 seemed like it might be such a knife.

Jim, I’m a little concerned now about the "Axis Assist". I’ve only seen pictures and videos of knife. They obviously don’t show anyone hurting themselves. How did yours bite you?

Sharpener1969: funny you should mention Phil. In collaboration with Phil, Spyderco will be making and selling a fixed-blade “Southfork” in S90V (FB30G). I pre-ordered one of those as soon as I saw it. My hope is it will be as close to a custom knife as I’ll ever be able to afford. Blade geometry looks and sounds excellent. Had they made it in M390 or CTS-20CP, I would have ordered it just as quickly, even if it had a Smurf blue handle. Fortunately, it looks more like hunter green.

KirbySDL, unfortunately I don’t know of anywhere close by where I could handle the 581. I am wondering a little about the handle thickness. It’s a bit wider than I’m used to. I’m sure it probably feels good in the hand and provides excellent purchase; but, I wonder how it feels in the pocket. Thanks for the quote from Phil too. (I didn’t know about the M390 bump.)

Two quick notes:

1) Do you have a source for the logarithmic relationship? The Wikipedia page for Rockwell hardness indicates a linear relationship between indentation hardness and tensile strength, but doesn't mention the specific relationship between either of those and the resulting Rockwell hardness value.

2) Even if the effective hardness between a 60 HRC and a 62 is large, it doesn't change the realities noted above: e.g. variances that can't be sidestepped even by manual processes, and the fact that BM neither makes customs nor charges for customs.

So there's the academic question, and there's the question of whether or not this is meaningful to an everyday knife user.

I'm interested too in knowing whether Rockwells are logarithmic as in the Richter scale. A 5.0 quake moves 10x more than a 4.0. Is a 61 HRC knife 10x or even 2x harder than a 60? I highly doubt it, as it would mean different samples of the same knife leaving BM would have a 4x-100x difference of hardness, which seems absolutely absurd.

That leads us to the second issue of whether it matters: probably not at all.

Significent,

My 581 "bit" me on closing. The Axis Assist closes as quickly as it opens. Close the blade to about 30 degrees and it slams shut. If you don't have your fingers out of the way you will be injured.

Jim Lucier

quote:

In collaboration with Phil, Spyderco will be making and selling a fixed-blade “Southfork” in S90V (FB30G). I pre-ordered one of those as soon as I saw it.

Could you pm me more info on this knife please .?

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Originally posted by jim Lucier:
My 581 "bit" me on closing. The Axis Assist closes as quickly as it opens. Close the blade to about 30 degrees and it slams shut. If you don't have your fingers out of the way you will be injured.

I'm also wondering how you did it Jim...I close my 580 two-handed, right pulling the Axis studs back, left closing the blade, no fingers near the edge in the process. At least I'd bet the cut was clean!