Spyderco m4 steel: Golden, CO vs Taichung, TW

[TennToadsticker]

I'm curious if anyone knows anything about how Spyderco's m4 steel produced in Golden (Manix 2, Mili, Mule Team) stacks up against that made in Taichung (Gayle Bradley). I wonder if there is any variation in HT or performance. Thanks for any information and insight you can provide.

 

[RevDevil]

It's stacks up the same. The steel comes from Crucible in the USA. They don't make CPM-M4 in Taiwan. The hardness of the steel depends on the specification called for based on the model.

 

[TennToadsticker]

Many thanks, RevDevil. HT is 64-65?

 

[kreole]

Rev is right it's all from Crucible, but I'm not sure they're heat treated before being sent to Taiwan, so there is a potential difference there. That said, I have the M4 Military and a Gayle Bradley, both used heavily, and I can't tell any difference in use (i.e., how long they stay sharp) or in feel when sharpening them. Talking hardness, Sal said the aim for the GB was 62-63 hrc (Mr. Bradley tested one that was closer to 65, though), and I saw an M4 Military tested at 63.3.

 

[RevDevil]

Many thanks, RevDevil. HT is 64-65?

I'm not sure what the hardness is, my apologies. I won't even pretend to know.
I will say that I read somewhere on the forums that the very first batch of Gayle abradleys were harder than subsequent batches.

 

[TennToadsticker]

I read that, too, but don't recall that it was ever verified by Sal or any other definitive source.

 

[kreole]

I read that, too, but don't recall that it was ever verified by Sal or any other definitive source.

GB 62 http://www.bladeforums.com/forums/s...PM-M4-HC-ZDP-189-M390-and-S30V-edge-retention
Military M4 63 http://www.spyderco.com/forums/showthread.php?45853-I-love-M4-steel-(Military-blade-hardness)
Sal showing their goal is 62-63 http://www.bladeforums.com/forums/showthread.php/702204-Bradley-Rc?highlight=bradley

 

[marthinus]

Gayle Bradley on his knife and M4 to about 64 HRC.

[video=youtube;eUJCWMgE7hk]http://www.youtube.com/watch?feature=player_detailpage&v=eUJCWMgE7hk#t=251s[/video]

The following is very important.

The problem with your theory is that blades from either range could come in at 61-63 in actual testing given the variables....

Rockwell testing is in general + or - 1 RC so 62-64 could in fact be 61-65 and 60-62 could be 59-63 so there is some overlap.

So in the end it depends on what they are shooting for and how tight they really want the RC range to be, that's why the ones who do post the RC data give a range.

The maker however depending on who is doing the heat treating and how good their furnace is can get them to hold the tolerances to + or - 1 RC so that would narrow down the variables somewhat.

That's if they don't overload the furnace to save money or aren't HTing more than one grade of steel at a time........

Lots of things can happen so I wouldn't take those numbers too seriously most of the time.

That's not even getting into how steels can change from batch to batch and those variables involved.

Not all makers can take on 10,000 LBS of one steel at one time.

I have access to a Rockwell tester and have tested the hardness of many of my knives.
*Jim Ankerson is right that, when comparing the results of two Rockwell testers, the results cannot be compared beyond ±1, because that is how accurate the calibration standards are. The machines themselves will measure to a fraction of a point. But machines calibrated to two different official standards are only good to ±1.

From my tests I have reached some conclusions.
1) Not all companies heat treat the same alloy to the same hardness. The hardnesses were far enough apart that they could not have been the same. You can even see that in the published hardness specs that some of the companies publish. I have seen specs showing AUS 8 as hardened to a 56-58 and others showing a 58-60. Jim Ankerson and Unit did an excellent job of explaining the reasons why knife companies sometimes choose a lesser hardness range for their blades.

2) I have never measured a blade hardness and found it to be outside the published spec of a manufacturer. Not all manufacturers publish their hardness specs, but I have found the specs which were published to be accurate.

 

[TennToadsticker]

Our plan was about 62/63. Gayle Tested one and he said it was closer to 65. CPM-M4 can take the higer hardness if that's so. We'll be doing a sample testing next week.

sal

I wonder if Sal ever got back in touch about the results of his test.

 

[gine]

Yes, the first batch that didn't have the texas logo on it were about 65 HRC...It was then changed to about 62.5 HRC....