A terrible mistake.
- Thread starter TomBartlett
- Start date
-
Hey Guest, Early bird pricing on the Summer Moot (29th July - 10th August) available until April 6th, we'd love you to come. PLEASE CLICK HERE to early bird price and get more information.
He's a good maker with a good rep ~ a big part of that good rep is wanting to know that there's a potential issue.
Don't be embarrassed ~ we all stuff up at some point and it's usually just moments after thinking something along the lines of 'Is this safe?'. If your issue highlights a potential heat treat issue, then you're doing him a favour by getting in contact with him.
A knife that could withstand being hammered into a tree and then have someone stand on the handle could have its blade broken by the twisting force of batoning a gnarly piece of wood.
A carbon Clipper is a very tough knife and will take this much abuse:
http://www.youtube.com/watch?v=y_HMDcMsamg&feature=player_embedded#at=526
..yet I managed to break the blade while batoning a gnarly section of Gorse:
A carbon Clipper is a very tough knife and will take this much abuse:
http://www.youtube.com/watch?v=y_HMDcMsamg&feature=player_embedded#at=526
..yet I managed to break the blade while batoning a gnarly section of Gorse:
There are any number of possible reasons why this could happen. there might be a chip on the edge which creates a stress riser, or there might be a flaw inside the steel, or it could be heat treat problem. This is why makers are usually very keen to get the parts back for examination.
Thanks for all the kind words of support. Martyn, I didn't see that video earlier but after watching it, I didn't put it through that kind of abuse. I'll let Mr. Orford know about what happened to the knife. Still feel kinda sheepish about doing it.
It is hard to tell from pics but it looks like it has an enlarged grain structure, if it has that would have been caused by heating too high over critical temp causing the grain to grow. IF it is large then it would have had an inherent weakness.
That being said, it is easy to overheat during treatment. (if that is what it is)
That is why you cant beat good ole differential heat treatment
That being said, it is easy to overheat during treatment. (if that is what it is)
That is why you cant beat good ole differential heat treatment
A knife that could withstand being hammered into a tree and then have someone stand on the handle could have its blade broken by the twisting force of batoning a gnarly piece of wood.
A carbon Clipper is a very tough knife and will take this much abuse:
http://www.youtube.com/watch?v=y_HMDcMsamg&feature=player_embedded#at=526
..yet I managed to break the blade while batoning a gnarly section of Gorse:
Ever seen the shape of a mortice chisel?
Its a very thick chisel that's designed to be hammered into wood and to prise the chips out.
Now notice that a knife isn't shaped like that at all. I never understand why on earth anyone would think that a knife should also be a ladder to climb a tree and can only cringe at the thought of someone putting their weight on it.
Bet if they snap it, what's left of the blade stuck in the tree could cause a hell of a nasty cut to the leg as the person comes down.
I understand that its one of the bushcraft experts who said that doing that was a good test of a knife?
I get the idea that he must have just been sick of people asking the same question and decided to take the mick a bit.
Its a gormless thing to do.
That's a real bummer. Next time you might consider buying a BattleBar from Hoodoo Knifeworks.
Ooooooooh bad beastie!
OK, here I go again, so feel free to go and do something more interesting instead while I go off on one...
Some years back I had a bunch of CPM-3V blades heat treated by Paul Bos (the absolute God of heat treating) through a maker friend as part of a batch he was having done.
I wanted to do some serious testing and needed any variables ironed out and for the tests to be as impartial as possible.
Interesting fact of the day - back when I had this done, Paul's default was to temper >10" CPM-3V blades back to Rc59 and <10" to Rc61
Let's run that by everyone again so the significance sinks in.
CPM3V is about as tough as knife steel can get. Far tougher than O1, far tougher than A2 (which itself is way better than O1), and even tougher than the likes of the bladesmiths favourite 5160
So we're talking about a material with native qualities of incredible toughness.
Or as tough as a big box of tough things that just graduated top of the tough class...
Now, despite its most prominent characteristic, the steel was (multiple) tempered back to 61 if under 10" long and 59 if over 10".
Now, let's come back to the typical bushcraft knife as we currently know it, Scandi ground in O1, hardened and tempered (often without a stress relieving cryo soak, or without multiple tempering cycles) to 60 - 62
Plain English:
CPM-3V, super tough steel, tempered to 61 by someone who is about the best in the business.
O1, infinitely less tough, tempered to the same range by any one of us lesser mortals who only wish we could come close to Paul Bos's standards.
Frankly, I'm amazed that we don't see and hear of this a lot more often than we do.
Recently I refused to make a knife for someone who requested a D2 blade tempered to Rc63. I told them it would break, but the customer knew better. After several conversations about it I flat refused to make what I was utterly confident would break, given D2's comparative brittleness and the customers intention to baton with it. Another maker friend told me a very similar story around the same time and for all I know we may both have been trying to get the same customer to see some sense. My friend made the knife, and it broke. The only one who seemed surprised was the customer.
Bend testing a knife to breakage is a minefield. If you apply the force rapidly the knife breaks more easily, and quickly, and at a much lower angle. If you apply it slower (as in the Enzo video Martyn linked to) the knife will bend and often separate from its handle slabs, and may bend quite some way before breaking. The same force applied rapidly though, would usually see the knife break at a much lower angle which, to the layman, might suggest a weaker blade.
Again, this is something I tried a long time ago when I was trying to understand what made blades break.
My own take is that a lot of people appear to have slightly unrealistically high expectations of knives when, in fact, the way in which they choose to use them is inviting failure and potential injury.
Building a seriously tough knife is possible, obviously, but not all knives are built tough by definition and a general rule of thumb is anything hard enough to take a hold a great edge is that much more likely to break when subjected to forces it was never meant to withstand.
Most of the Cold Steel knives I have Rockwell tested over the years have rarely been harder than around Rc56 and many have been Rc54. The 'high performance' of their knives mainly centres around their toughness, and the comparatively low hardness (by today's standards) is a large part of that equation.
What people are missing though, is the grind and its effects on the whole picture. Good edge geometry can allow a softer blade to appear to have equal or greater edge holding because the actual edge itself doesn't do a lot of the work, and Cold Steel nailed that a long time ago.
You can't achieve the same thing with a zero Scandi ground O1 blade, period.
I am not trying to an apologist for the maker or suggest that we should all expect our cutting tools to imminently fail, but I feel very strongly on this.
A good file can break if you drop it onto a stone floor and the file is likely to be around or, at most, a couple of points harder than your typical O1 bushcraft blade. Anyone beginning to see where this might be heading yet ?
No, where did I leave my coat this time ?
Some years back I had a bunch of CPM-3V blades heat treated by Paul Bos (the absolute God of heat treating) through a maker friend as part of a batch he was having done.
I wanted to do some serious testing and needed any variables ironed out and for the tests to be as impartial as possible.
Interesting fact of the day - back when I had this done, Paul's default was to temper >10" CPM-3V blades back to Rc59 and <10" to Rc61
Let's run that by everyone again so the significance sinks in.
CPM3V is about as tough as knife steel can get. Far tougher than O1, far tougher than A2 (which itself is way better than O1), and even tougher than the likes of the bladesmiths favourite 5160
So we're talking about a material with native qualities of incredible toughness.
Or as tough as a big box of tough things that just graduated top of the tough class...
Now, despite its most prominent characteristic, the steel was (multiple) tempered back to 61 if under 10" long and 59 if over 10".
Now, let's come back to the typical bushcraft knife as we currently know it, Scandi ground in O1, hardened and tempered (often without a stress relieving cryo soak, or without multiple tempering cycles) to 60 - 62
Plain English:
CPM-3V, super tough steel, tempered to 61 by someone who is about the best in the business.
O1, infinitely less tough, tempered to the same range by any one of us lesser mortals who only wish we could come close to Paul Bos's standards.
Frankly, I'm amazed that we don't see and hear of this a lot more often than we do.
Recently I refused to make a knife for someone who requested a D2 blade tempered to Rc63. I told them it would break, but the customer knew better. After several conversations about it I flat refused to make what I was utterly confident would break, given D2's comparative brittleness and the customers intention to baton with it. Another maker friend told me a very similar story around the same time and for all I know we may both have been trying to get the same customer to see some sense. My friend made the knife, and it broke. The only one who seemed surprised was the customer.
Bend testing a knife to breakage is a minefield. If you apply the force rapidly the knife breaks more easily, and quickly, and at a much lower angle. If you apply it slower (as in the Enzo video Martyn linked to) the knife will bend and often separate from its handle slabs, and may bend quite some way before breaking. The same force applied rapidly though, would usually see the knife break at a much lower angle which, to the layman, might suggest a weaker blade.
Again, this is something I tried a long time ago when I was trying to understand what made blades break.
My own take is that a lot of people appear to have slightly unrealistically high expectations of knives when, in fact, the way in which they choose to use them is inviting failure and potential injury.
Building a seriously tough knife is possible, obviously, but not all knives are built tough by definition and a general rule of thumb is anything hard enough to take a hold a great edge is that much more likely to break when subjected to forces it was never meant to withstand.
Most of the Cold Steel knives I have Rockwell tested over the years have rarely been harder than around Rc56 and many have been Rc54. The 'high performance' of their knives mainly centres around their toughness, and the comparatively low hardness (by today's standards) is a large part of that equation.
What people are missing though, is the grind and its effects on the whole picture. Good edge geometry can allow a softer blade to appear to have equal or greater edge holding because the actual edge itself doesn't do a lot of the work, and Cold Steel nailed that a long time ago.
You can't achieve the same thing with a zero Scandi ground O1 blade, period.
I am not trying to an apologist for the maker or suggest that we should all expect our cutting tools to imminently fail, but I feel very strongly on this.
A good file can break if you drop it onto a stone floor and the file is likely to be around or, at most, a couple of points harder than your typical O1 bushcraft blade. Anyone beginning to see where this might be heading yet ?
No, where did I leave my coat this time ?
Last edited:
Barry, genuine question. With regards to toughness, why are live swords still typically made from carbon steel (or variants of), and never to my knowledge from CPM-3V (or variants of)?
Last edited:
I think you probably know just how big a question that is Martyn, but I'll take a crack at some of the factors anyway
The short and most accurate answer: I don't know, but I suspect economics forms a large part of the problem.
The longer version, based on my own methods/experiences and what little knowledge I have of the mass produced factory stuff in the world:
The simple carbon steels are inexpensive, readily available more or less everywhere in the world except the UK
and they are easy and inexpensive to work. For factory produced blades availability and cost to buy and work are key in profitability.By comparison a lone blademsith will normally adopt a material of personal preference largely based on his or her familiarity with it and how well they can get repeatable results in heat treating.
Think along the lines of Howard Clark's L6 katana's. Take away his heat treating wizardry and the product would never be the same.
Spyderco's rationale for not making the new Bushcrafter in something other than O1 was quoted as cost issues in getting a suitable (and arguably better (subjective)) alternative to the country of manufacture.
I think most folks stick with their own winning combination of what is available combined with what they can effectively work with to produce repeatable results at what they consider to be the right level.
Speaking for myself, quite simply, I just can't source CPM3V in the UK at a price that makes it a viable option, or in sizes that make it particularly attractive. I do have loads of various 10x series, L6 (real L6 and not the 15n20 so-called equivalent) and all kinds of others, and I am happy with the end product (my customers appear to be too).
For a solo bladesmith this present issues of sourcing materials that are costs effective and then ditching what may amount to decades of tinkering with their current preferred steels to start from scratch learning how to get the best from a new (to the smith) alloy. If you are self employed as a bladesmith (either partially or fully) then you have nobody to fund this but yourself, which can be a tough call to make. If you are a hobby maker your pockets have to be deep...
A lot of swords are made from CPM3V and some sword makers are suggesting that CPM3V may be the single best commercially available steel for large blades currently available. That makes absolutely no difference if you just can't get your hands on it for personal use, or if shipping tons of it would drive up the unit cost for your small factory in goodness knows which country for producing runs of swords, or...
Those makers using it say they often have difficulty finding useful/appropriate sizes...
If S30V was as available as O1 and as simple to heat treat we'd all be using it. The popularity of O1 is largely down to the fact thta it is so readily available. Even if it didn't make a good knife folks would still be using it because they can get it. Happily it does make a good knife (all things being equal) but makers can't use what is difficult or particularly costly to get; especially those who recycle coil and leaf springs and what not. We'd all like to be grinding on BurrKing, Wilton or KMG grinders but the cost to get them over here is prohibitive. I've owned BurrKing and Wilton before and I can honestly say I didn't grind any better on one than I do on my home-rolled metal-muncher, but you get my point.
I think most of us have little choice but to draw a line in the sand at our respective "this is the absolute best that I can do" points.
Like I said, I don't know, but I can put a few educated guesses on the table.
EDIT:
My sincere apologies to the TomBartlett, for so thoroughly going off on one in his thread.
My comments were certainly not meant to criticise, inflame or in any way increase his misery.
I hope he finds a resolution or suitable way forward, and I am also a little concerned that this was my 666 post...
Last edited:
Xunil, the whole reason I take part in this website is to try and learn new things, so no need to apologise. My misery is in no way inflamed, but then again, that might just be because I didn't understand a great deal of what was just said
I was googling for similar instances of this failure mode and came across this image of a broken bushcraft knife. Unfortunately there isn't a photo of the end-grain, so we can't compare the crystalline structure, but it's a remarkably similar break. Can anyone shed any light on the forces involved in this failure?
I was googling for similar instances of this failure mode and came across this image of a broken bushcraft knife. Unfortunately there isn't a photo of the end-grain, so we can't compare the crystalline structure, but it's a remarkably similar break. Can anyone shed any light on the forces involved in this failure?
It was accidentally dropped on some rocks and driven over by a small tractor with a lawnmower attachment on the front, pulling a trailer loaded with firewood. A lot of firewood. As in, 8 feet long and 4 wide of heaped high trailer's worth of firewood.
I know this because I made the knife and was there when my uncle drove over it
Basically the tip of the knife was wedged against one rock and the other end against another, and the blade gave under the weight of the ATV/tractor/load.
So you might say the forces involved were excessive...
Here it is on one piece:
I still have the bits in the workshop - they are both a little shorter, from running some tests on the area where the blade broke, and I've often thought about turning the tip section into a broadhead.
The blade was not selectively tempered and was around Rc60 all the way through, triple tempered with a 24 hour liquid nitrogen soak after the first tempering cycle. From memory the steels were 1090 and L6, but I couldn't swear to that (I made it quite a few years ago now).
Here are a couple of images of what remains of it, taken a few minutes ago:
I tried breaking it again and cut some slices off for further testing, so there really isn't very much left now.
It was a great slicer, and very comfortable in the hand, and I keep meaning to make another in that pattern.
Not so good at being run over though
I was inventing profanities on the spot the day it happened Ged.
Uncle was in the bad books for some time after as I recall - he'd aparently left the knife on the front of the mower attachment when doing some cutting chore or other, and as he drove away he heard something rattle and bounce through the machinery. Never thought to stop and take a look...
Uncle was in the bad books for some time after as I recall - he'd aparently left the knife on the front of the mower attachment when doing some cutting chore or other, and as he drove away he heard something rattle and bounce through the machinery. Never thought to stop and take a look...
