CPM3V and chipping

spyken

spyken

Joined
Apr 29, 2002
Messages
5,567
My CPM3V bushcraft chipped in 3 places (about 1mm deep) whilst it was being used to pry off some hard candy out of a jar. I was a bit surprised that it chipped since 3V is supposed to be tough steel. I tried to sharpen out the chips, got 2 out, the last one is a little too deep and I don't want to remove too much metal.

Has anyone of you experienced chipping in your 3V blades?

One thing though, I had to spend a lot of hours trying to sharpen that scandi blade...:grumpy:, I think I will stick to full flat grind from now :p:D
 
Spyken: I dont have a Koster 3V yet, just waiting for one of the budget Bushmasters that we both bought if I recall correctly. I also have a Koster 3V MUCK on pre-order and another custom 3V in final sketch stage from another knife maker.

My desire for 3V came after buying a custom Justin Gingrich 3V Hunter off the Exchange and using it (almost abusing it) extensively to see how it would hold up. I was amazed with its lightweight, toughness, corrosion resisting, and edge holding capability. I was using a 2lb plastic face hammer to hammer the spine & tip into 8" diameter green bamboo at 90 degrees. No chips or rolls.

The edge is convex not scandi. I maintain the edge by machine stropping which takes 2 minutes at most. I use two buffing wheels, one with red compound and the other with green. I just touch the edges, red first, green second and its done. Sharp strong edge in seconds off the wheels.

With 3V and buffing wheels, I found that you can get an edge that is too sharp to feel by hand.

Of course the wheels will not work with the scandi, but should be ok for the Bushmaster and MUCK.

I will use my Bushmaster when it arrives and will let you know how it goes.
 
Well, as I recently procured myself both a Koster Bushmaster and a M.U.C.K., both in 3V, I sure hope the heat treat is correct on these. I know 3V to be good, tough stuff, but if the Rockwell is too hard...???
 
Lateral stress will chip nearly any steel - regardless of grind. I can't say for certain that that is the case here - without seeing the knife and testing the steel. But nearly every time I have chipped a knife's edge, it was from lateral stress (twisting the blade, or sideways movement during cutting). I do beat/wail on my own stuff now and then...practically void my own warranty...LOL :eek:


What I can say, however, is that I have had many many buyers beat and wail on Bushcraft knives in 3V - including heavy batoning - with no resultant chipping.

Chipping in 3V is extremely rare. There is a chance there was a fault in the steel or it might have occured from the strange use of the knife. :p

One of the primary reasons they made 3V was to reduce the possibility of chipping. You can read it for yourself right here in the manufacturer's own words:

http://www.crucibleservice.com/eselector/prodbyapp/tooldie/cpm3vt.html

CPM 3V is a high toughness, wear-resistant tool steel made by the Crucible Particle Metallurgy process. It is designed to provide maximum resistance to breakage and chipping in a high wear-resistance steel. It offers impact resistance greater than A2, D2, Cru-Wear, or CPM M4, approaching the levels provided by S7 and other shock resistant grades. CPM 3V is intended to be used at 58/60 HRC in applications where chronic breakage and chipping are encountered in other tool steels, but where the wear properties of a high alloy steel are required.
Click to expand...


I have all my CPM 3V hardened (and tested) to 60 HRc. Always have, always will. It is the *sweet spot* for that steel. Anything else would be a compromise. Higher HRc results in less toughness and lower HRc results in drammatically less wear-resistance (edge-holding).

I think I have made at least 600 knives in CPM 3V and I can think of 3 failures (including yours). I have yet to be able to pin the fault on steel or a poor heat-treat.

It really is such an amazing steel....a true *super steel*.

:thumbup:

Dan
 
Dan, thanks....there was digging of the hard candy, so that may be the torque. We'll use it (my friend and I) for a bit yet....because I've just put a crazy sharp edge on it, then maybe once we've beat on it a bit, I'll send it to you for examination and a resharp.

I'm looking forward to my Bushmaster :)
 
Yep, it doesn't matter what the steel is--when it's nearly as hard as a file and thin as it has to be to make a sharp edge, it can't stand up to prying use. Cutting (slicing, batoning or anything else) is directly in line with where the edge is strongest, with the strength of the whole blade supporting it. Turn it sideways, though, and there's almost no material there. The spine of an 1/8" thick knife is probably 100 times stronger than the edge is, more or less, depending on the angle the edge is ground at.
 
Does anybody know the Rockwell hardness of "hard" candy?
As a kid we used to melt sugar into dark brown, slightly burnt mass of clear sweet goodness on a sketchy Bunsen burner which would congeal to Rockwell hardness just about hard enough to shatter any 10 year olds tooth????-that's got to run way off the Rockwell scale.
P.S.-My dad never asked me why I wanted a gallon at time of denatured alcohol from the hardware store!
I learned all this Bunsen burner stuff from my 1971 Sears Ultra-Ultra-Deluxe Chemistry set!-best Xmas gift ever!!!!!
I still have a gallon of denatured alcohol on the shelf!!And the Bunsen burner-just in case.-lol
 
I'd be interested to know how hard, hard candy is :p

Thing about scandi edges is that there is a lot of material behind the edge, more than a flat ground blade with 0.02" edge thickness (let's not compare with Busses with 0.05" edge thickness, haha), so the chipping surprised me. Damn, has anyone considered making knives out of hard candy? hehe...

BTW, how do you guys resharpen your bushcraft knives? I used a cheap extra coarse caborundum stone, followed by 120/400 grit waterstone and some sandpaper and some stropping to finish it (that's all I have as my set-up).
 
The other question, really, might be if contact was made with the edge or lip of the glass jar. Glass is much harder than steel!

I have mashed an edge and a tip on two knives with accidental contact with glass cups.
 
Same thing for me !
My CPM3V bushcraft chipped vs some pieces of wood... hard wood !!
French ash :)

i think 60 HRc is too hard ....

many people buy knives and do not use them maybe that's why CPM3V bushcraft had only 4 failures.
 
I am wondering this very question myself on the Bushmaster , as I am about to pull the trigger on one also. Dan makes some awesome knives and knows the ins and outs of Cpm3v well I'm sure , but I would like some user feedback on the knife as well.:)
 
I just recieved my Bushmaster from KSF a couple of hours ago. Can't tell you about chipping as I've yet to use it, but its a very solid knife that inspires a lot of confidence, and the edge is ground pretty robustly (looks like about 40 degrees inclusive). Its also very well balanced. My one gripe with the Bushcraft is that it is handle-heavy, but the skeletonized handle on the Bushmaster means it balances perfectly on the first finger despite the large handle.
 
Thanks Brummie. I'm seriously thinking of getting that knife , despite the many I already do own. I have a 4 1/2" EDC in nat'l micarta of Dan's that is one helluva knife and works great in a bushcraft role also. Decisions loom again ,lol.
 
His conclusions are flawed and don't apply to the knives I make. He makes "thin hard blades...not choppers" and prefers "wear resistance over toughness". He heat-treats blades himself and I can tell you from personal experience that a professional heat-treater has a higher success percentage than doing it yourself. So he's going to get a failed blade now and then. Happened to me...happens to everybody.


When in doubt, head to the source for the facts:

http://www.crucible.com/eselector/prodbyapp/tooldie/cpm3vt.html

3V at 60 is still a "70" on the charpy (toughness) test...not a "50" - as he states.

Also, a "70" is still miles ahead of other knife steels - which are mostly in the 30s/40s.

cpm3vcompgraph.gif


Besides, it's a moot point as I tell my heat-treater to aim for 59/60 anyway....which is what the link above hints at being ideal.

You'll notice too that he says he aimed for 60/61 when he got chipping - which is indeed too hard.

If you call Paul Bos or Peter's heat-treat as ask them for the best heat-treat they can give 3V, they will say 59/60. If you call SB Specialty Metals (maker of 3V) and ask for the best heat-treat numbers they will say 59/60. I don't think there can be any better sources for information on heat-treat than the maker of the steel and it's primary heat-treaters.

There have to be around 1200 knives of mine in 3V floating around out there. If there are chipping issues, no-one's telling me about it. I've only had a few emails about it and they were all resolved to be operator-error (dropped knife, hitting something hard, prying, etc.)

Naturally, I'd be very surprised to see any chipping on any BushMasters. And, of course, if anyone does get any, please send it back for a FULL replacement.

Thanks!

Dan
 
Last edited:
Daniel Koster said:
I don't think there can be any better sources for information on heat-treat than the maker of the steel and it's primary heat-treaters.
Click to expand...
Thanks, Dan. That's good enough for me. :thumbup:

PS: I just ordered a BushMaster from KSF. :D
 
Last edited:
Same here. Thanks Dan . That looks like one outstanding knife I really have to get :thumbup:
 
It's possible to chip or even break the tip off of a 3v steel knife.

However I think you are way less likely to do so with 3V than any other type steel.

Of the knives I have in scandi the 3v ones hands down are the toughest.
 
You must log in or register to reply here.
Back
Top