Spyderco Forums

kbuzbee · #41

JNewell wrote:For what it's worth, the "other company" that does a lot of M4 blades has raised its target Rc range for M4 blades to 62-64Rc in the last year or so.

Interesting. Thanks for the update. I hadn't heard that.

Ken

#42

Hi Wolverine,

Your quest for knowledge of steel is large and deep. No simple answers. Info found here is probably as good as anywhere. Some very knowledgable folks here. But it's still time consuming with info degesting slowly.

CPM-M4 is one of the earliest powdered steels Crucible worked with. It was "resurrected" by Gayle Bradley, Warren Osbourne (both excellent makers) and Scott Devanna (who was a rep for Crucible at the time). They were focused on competition knives and their many hours of research showed clearly with Gayle Bradley winning the world championship twice with CPM-M4.

CPM-S30V on the other hand was created as a blade steel from the beginning.

Now with many foundries competing in high performance blade steels, the choices of materials is much greater as is the treatment of these steels. Heat treat, edge geometry and materials tested offer much variation.

sal

Wolverine666 · #43

Hi Sal ,
Thanks for the info. I find the various steels used for blades to be extremely interesting. And you are correct , my quest for knowledge knows no bounds.

Also , I always feel privileged any time you contribute to my post. It's like talking about lightsabers and all of a sudden Yoda joins the conversation. I love it :)

Thanks again.

Cliff Stamp · #44

The Mastiff wrote:What the competition chopper goes through does not compare in any way to what the folders we carry go through.

The competition choppers are not hardened in the same way that Spyderco (or anyone else) hardens the folders, it is thus of no use to attempt to extrapolate data from one to the other because they are essentially different steels at that point.

The competition choppers were first hardened using the standard cycles for CPM-M4 and it resulted in gross fracture of the blades. The heat treatment was severely adjusted to significantly underharden the blades to vastly increase the toughness by reducing the alloy that went into solution.

There is also no way that wear resistance is of significant use when you are cutting, 1-2 piece of 2x4, 1-2 pieces of rope and then straws, bottles, etc. . These contests are amazing displays of precision which can't be appreciated until you actually attempt to do some of the cutting, but they are not significantly demanding on the blades.

Note that anyone who actually does chopping work with a large blade would cut more wood in an afternoon than a competition chopper would in an entire year. What does that tell you about the lifetime of a CPM-M4 large blade for actual working blades?

Remember while CPM-M4 is promoted as tough, this is tough for a high speed steel, not tough in general.

Alchemy1 · #45

I love(ed) my GB, but that love has lessened with my latest use. I decided to finally sharpen up my GB on my Wicked Edge because of this thread. I sharpened it at a 40° starting with 100 grit stones and going all the way up to leather strops loaded with 5 and the 3.5 micron paste. This gave me an edge that was mirror polished with minimal scratches still present.

Right off of the sharpener I could tell it didn't feel as sharp as other knife I have sharpened at the same angle and with the same process. So, I commence to slicing copy paper. It did okay, but was still noticeably duller than other freshly sharpened blades. I broke down the box that my
Yeti Tundra 50 came in using the freshly sharpened GB.

About halfway through breaking down the box I could feel the resistance increasing. I was cutting with the corrugation of the cardboard. After breaking down the box the tip, which wasn't used much cut paper like it did in the beginning, but the heel of the blade would barely cut the paper and often tore it.

DeathBySnooSnoo · #46

Sounds more like a sharpening issue rather than a steel issue. Maybe a wire edge?

M4 has far better edge retention than a lot of the steels we see used. And I have used mine a lot harder than that and still been able to shave with it never mind jsut slice paper.

Cliff Stamp · #47

Alchemy1 wrote: So, I commence to slicing copy paper. It did okay, but was still noticeably duller than other freshly sharpened blades.

...

After breaking down the box the tip, which wasn't used much cut paper like it did in the beginning, but the heel of the blade would barely cut the paper and often tore it.

That isn't the steel, even a basic stainless like AISI 420 can cut far more cardboard and still slice newsprint, let along thicker paper easily. The edge wasn't formed properly.

Alchemy1 · #48

I plan on throwing it on the WE again to touch up the edge. I'll report back. I'm no sharpening expert, but I have done a decent amount of sharpening on this system and have not had this issue with any other knife. I'll report back.

kbuzbee · #49

Did you feel for a burr at each grit? On the WEPS in particular, I can always feel the burr at each level. Once I get into the finer grits (800 and above) when I think I'm ready to move on, I gently wipe the edge with a tissue. It will leave traces if I have any burr/wire I can't feel with my fingers. Just a thought...l

Ken

gaj999 · #50

Alchemy1 wrote:... I sharpened it at a 40° starting with 100 grit stones ....

40 degrees per side, or 40 degrees included? I run mine at 20 degrees included(10 degrees per side) and love it.

Gordon

#51

Hi Alchemy1,

10X-12X loupe, #1 teacher.

sal

Ankerson · #52

Cliff Stamp wrote:That isn't the steel, even a basic stainless like AISI 420 can cut far more cardboard and still slice newsprint, let along thicker paper easily. The edge wasn't formed properly.

I agree, something going on with that edge.

Alchemy1 · #53

40 inclusive...20 per side. I run my finger over the edge before I switch sides of the knife and when I'm going to change grits. I only work one side at a time until I can feel the burr. Before I change sides I shine a flash light down the side that has been worked with the finer grit and compare that to the side that has been worked with the coarser grit. If it looks like the finer stone has done its job and I can feel a burr I move to the other side. Once I switch sides I work until I feel the burr again and then I look with the light and compare the scratch patterns on both sides. If the second side matches the first I know my work with the finer stone has been successful. I repeat these steps with each grit/side.

chuck_roxas45 · #54

Alchemy1 wrote:40 inclusive...20 per side. I run my finger over the edge before I switch sides of the knife and when I'm going to change grits. I only work one side at a time until I can feel the burr. Before I change sides I shine a flash light down the side that has been worked with the finer grit and compare that to the side that has been worked with the coarser grit. If it looks like the finer stone has done its job and I can feel a burr I move to the other side. Once I switch sides I work until I feel the burr again and then I look with the light and compare the scratch patterns on both sides. If the second side matches the first I know my work with the finer stone has been successful. I repeat these steps with each grit/side.

I've seen another person who claimed the same problem. I guess the best thing for you to do is to send the knife in to Spyderco so they can examine it. I would also be interested in the results since the other person refused to send in his knife.

Alchemy1 · #55

I'm going to resharpen it again to make sure it's not me. I'm not a professional, so it's possible it's user error, but I'm pretty through when sharpening. The only thing I don't do is use magnification.

When I get some time this week I'll throw it back on the WE and go from 800 grit back up to the strops. If there is a burr that should be plenty to take it off.

chuck_roxas45 · #56

I also kinda had a bit of a problem until my second reprofile. Could have been powered sharpening weakened steel from the factory.

kbuzbee · #57

Alchemy1 wrote:I run my finger over the edge before I switch sides of the knife and when I'm going to change grits. I only work one side at a time until I can feel the burr. Before I change sides I shine a flash light down the side that has been worked with the finer grit and compare that to the side that has been worked with the coarser grit. If it looks like the finer stone has done its job and I can feel a burr I move to the other side. Once I switch sides I work until I feel the burr again and then I look with the light and compare the scratch patterns on both sides. If the second side matches the first I know my work with the finer stone has been successful. I repeat these steps with each grit/side.

Sounds about what I do with one addition. After doing each side in the same way you do, I run each side in sequence very gently. Left-right-left... Maybe a dozen passes total. Then I move on to the next grit. Dunno, but maybe something to try?

Ken

DeathBySnooSnoo · #58

I find that using light pressure after sharpening and running your edge down a piece of wood helps too. If it still feels sharp after a few passes then you should be ok, give it a strop and go, if it seems to dull a fair amount, you had a burr or wore edge and so go back and resharpen.

Cliff Stamp · #59

Alchemy1 wrote:I repeat these steps with each grit/side.

A burr which is biased enough to the side for you to feel it indicates serious amounts of weakened steel are left on the edge. CPM-M4 should not burr easily or significantly as is it hard, fine aus-grained, and has small and widely dispersed carbides. In any case, in order for the edge to be sharpened cleanly the burr has to be removed.

To be frank, forcing a burr, while useful when learning how to sharpen should be one of the first things to move past. The goal is to just apex the edge with minimal burr, ideally never enough of one to see or feel and just be limited to the extent of what the steel can cleanly form, which to date appears to be on the order of 0.1 microns.

I would suggest :

-grinding a light flat along the edge of the knife to remove all weakened metal, just 1-2 passes on a UF stone is enough

-start with a medium-fine stone and work just until the edge no longer reflects light, do not force a burr

-if you wish, keep increasing grits however make sure you remove any burr which forms by accident

Jet B · #60

I also use a Wicked Edge. Not saying you are doing anything wrong, just posting what I do. Most of what I learned was from watching Clays video tutorials and reading up on it.
I only bother to form a burr if I'm re-profiling a new edge. And then I only do it with the coarse stones during the initial regrind. Once you are at the edge, you are there and the rest of the grits are just cleaning it up and go very quick. Forming a burr with each grit afterwards is really just wasting your time and steel. I don't really look for the burr either, I use a sharpie and just go until it's all removed, then just feel the slight burr after a couple passes on each side. Each sequential grit only takes enough time to just replace the scratch pattern with the finer cut. I then do spend more time on the strops just because I enjoy making the edge sticky sharp and micro-convexing it.

Who knows, maybe there is something wrong with your steel. Also, make sure you don't have a set of the faulty clamps with the bad heat treat. If your jaws are bent on one side, it will screw your angles and edge up. They will quickly send you replacements if this is the case.

I like Sal's suggestion about the loupe. Nothing beats actually looking at the edge to see what's going on.