Spoke to Spyderco Technicians about M4, Maxamet, and Rex 45

S

Sharperthansticks

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I sent in two knives to Spyderco for maintenance, one of which was a Manix 2 in M4 which, I thought, had chipped way too easily. A Spyderco technician called me today and asked me about my sharpening methods, and I explained that I used a WSKO + blade grinder attachment, with the last passes of the blade going on 6000, 12000, and green compound-embedded belts (in that order). He told me that the reason I am experiencing chipping is that M4 has large carbides and it should not be sharpened past somewhere between 800 and 1000 grit belts. He also said that he sees this issue with M4 about once a month. So then I asked him about Maxamet and Rex 45, and he said that the same guidance (about stopping somewhere at around an 800-1000 grit belt ) applies to those, as well. Anyway, figured you guys would want to know this.
 
Good to know.
Thanks for sharing.
I wonder if diamond makes a difference.
 
miso2 said:
Interesting!
Did he elaborate the rationale?
Click to expand...
He may have, but I don't remember, and I don't like to say things that I can't stand by. (Saying only as much as you are sure of is a good policy.) The technician asked me about my sharpening methods, and I think he wanted to exclude diamonds as a possible cause of my problem. I don't know if it's because diamond grit exceeds 1000 or if it's because of another reason. When I told the guy that I was using regular belts, I think he referred to it as "conventional abrasive" (instead of diamond abrasive).
 
I hand sharpen my M4 blades to 2000 grit and then strop on green compounded leather and have never experienced any any chipping problems. I sharpen to around 15 degrees too. I remember you mentioning this and find it odd that your Manix chipped out. I have experienced edge damage, but it was more rolling of the edge, than chipping out.
 
Interesting to know. I use the same setup, and I've heard similar things before about these steels - but typically in reference to grind angles, not grits.

My understanding (as basic and likely highly flawed as it is) is based on imagining the carbides as microscopic hard chunks embedded in the alloy that contribute to the wear resistance. As you bring the angle farther down - or apparently the grit up as well - you end up with a reduced amount of supporting softer (tougher) alloy around the chunks of carbide, and thus less keeping it in place to prevent breaking off. This would be part of why particle metallurgy (spray-formed) steels have generally higher toughness, as the carbide distribution is more uniform throughout the alloy and you're less likely to get clumps of carbides together that are less resistant to impact / breakage.

That's how I visualized it, anyway. No idea how close to reality that is.
 
I admit that I can't tell the difference between chipping and a rolling spot, so let me clarify what I mean when I *may* be mistakenly saying "chipping": I mean that, when the edge is examined under a light, up and down and left to right, there are one or more sparkling spots, indicating that the edge has either been ruptured (chipped) or deformed (rolled).

The information that I've given to explain this phenomenon is from Spyderco. You are free to disagree with Spyderco.

With regard to what Comeuppance Comeuppance said, yes, I think you are right. If I remember correctly, when reading on this topic, I found out that larger carbides result in tougher steels, presumably because larger forces are required to knock those carbides out of place. One trade-off is how sharp you can make your blade, though, since this is limited by the largest particle in the steel. I imagine the carbides as similar to the teeth in our mouths, and the rest of the steel as the bone and gum. If you strip away the bone and gum (which is analogous to sharpening to a finer and finer grit), the teeth have little supporting structure, and it's easy for them to fall out (which is what we call periodontal disease, incidentally). It's not a perfect analogy, but maybe it's good enough.
 
I beleive I read a post about the carbides being ripped out of the alloy. Something about the sharpening medium not being tougher than the carbide. This would remove the softer alloy around the carbides. This in turn pulls it out instead of removing material from the carbide. Perhaps higher grits arent sharp or stong enough to remove material from the carbide. Also the teeth analogy makes sense . I think I just repeated what everyone said.
 
I don't know about all this powered belt sanderness.
Sounds like I'm very glad I don't have one (once again).
I don't get all chop and pry with my M4; I just use them to cut abrasive material at work.
Gee I can't imagine not sharpening them to my norm of Shapton Glass 4000 (which is a half fast mirror if you only look quick out of the corner of your eye).

What does he mean by that ? What's the point?
Well held opposite a light it reflects light back in a very satisfying way and looks mirror like. When I look at it with my Jeweler's visor it looks kind of hazy and scratched but shinny too.

Whittles hair quite easily, cuts stuff I need to cut with surprisingly low drag on the bevels.
That's all I really care about.

Bottom line : zero chips, zero rolled edges, super controllable carving / paring / trimming cuts for weeks and the edge only very, very gradually gets a little duller.

I'm sticking with my >1000 grit sharpening media.
Hahahah I sound like a real dumb bunny when I say I was reading last night that M4 has 4% Vanadium. I hadn't grasped that before. From all my messing with the S___V "high Vanadium" alloys I would assume I need diamonds to even touch up the M4.
Not the case at all and I have a ton of use on my three M4 users.
Trying to touch up or sharpen my S30V the same way I do my M4 would be just a waste of time and I would be walking around with dull sucky S30V.

I don't want to look too close at this I'm just thanking the Knife Gods there is M4.
 
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