Swordmaking Taboo: Blade Straightness / Temper / Flex Tests
Aug 22, 2014 23:39:30 GMT
Post by Brendan Olszowy on Aug 22, 2014 23:39:30 GMT
Hi Folks
I want to bring something up. I feel the public have been misled. And it's a misunderstanding propagated by certain 'authorities' on swords, certainly the free online media, and propped up by some misguided advertising on the part of certain manufacturers. It's another 'fad' in the sword communities upon which I, via my experiences over the last 8 years, stand in disagreement.
And I want to bring it out of the proverbial darkness of sensationalism and hype and layman’s gospel into the light of the reality in which I live.
I'd like to hear other swordmakers, like Jeffrey, Lukas, Seth et al. come out with their supportive or non-supportive experiences too. And comments by the ommunity are welcome.
Let me pre-qualify this by saying that there are obviously people here that know this stuff, perhaps experientially by their own foibles or folly. But the myth is on encountered or misunderstood by most noobs, and its an unhealthily pervasive untruth, or half truth. Some these videos by manufacturers show extreme flex 'testing' without showing the after effects being a sadly bent blade, thought surviving from breakage, which was the intention all along, not the the result be a perfectly straight blade, but these aims not necessarily made clear beyond the spectacle of the bending of the blade.
So after seeing some shocking manufacturer you tube recently, and reading some awful newby naivety on SBG Facebook, I felt compelled to write this...
The Falacy: in a nutshell.... It has been misrepresented to the public that a well hardened and tempered blade wants to be straight, and will withstand strong flexes and return to true.
Whats worse, you've been encouraged that this is a tool available to the general public that you can use to 'test' the temper of your sword.
I disagree, conditionally...
Nota Bene (NB): Before we start, the reader is assumed to have an understanding of heat treatment and it's correct terminology.
*The processes in sum are referred to as Heat Treatment, or HT for short.
*Hardening refers to the quench, a blade at 840 - 890C is rapidly cooled by submersion into a coolant. (Initial temp variance for allow type - low alloy > lower heat, high alloy > higher heats)
*Tempering refers to the release of stressed in a quenched blade via heating to lower temperatures of 200 to 400C depending on the aim of the maker. This can be performed in all manner of methods.
Thats all I want to discuss on that topic.
The Reality:
Ok sword buying public; please understand this is what really goes on. It starts at the quench… nay, it really starts at the foundry… Yep, even foundry steel comes to the maker with a pre-set memory. It’s not visible until one tries to work with the steel. Even cutting blade blanks from flat bar can reveal that the flat bar actually ‘wants’ to sabre. Once I made a cut where one side closed down into the other side so hard that it grabbed my angle grinder fiercely, launching it out of my grip, cutting into my hands I almost lost a finger, but for the joy of plastic surgery and Australia’s great public healthcare system.
Ok, so we’re fighting the memory in the steel to begin with….
Then we sword makers of esteemed patience and craftsmanship make a sword form which is crafted to perfection in every plane. Awesome straightness smoothness and geometry. It's great, we pour out our talent and patience through magical hands, forging, grinding, drawfiling this steel into an ostensibly perfect blade form. But then, sadly, we have to turn our fine creation over to the elements, by heating it into a plastic, semi liquid state, and then snap freeze this long and complex shape, causing all sorts of variety of stresses inside the blade at a mollecular level.
Now, providing we’re in luck we have good molecule structure transformation (i.e. hardening) and our sword is not a pretzel and didn’t crack. I’ve never had a blade crack in quenching, but they almost without exception will take a variety of sets. Blades set, sabre, and crack because the process of molecule transformation is not uniform over the length nor breadth of the blade. Expensive and elaborate technologies have been developed to try to eliminate variables and try to make for the most uniform transformations possible. But this high tech equipment is beyond the access of all but a few swordmakers. These may include the use of salt baths, rather than forges, furnaces, or kilns for heating. There are even vacuum chambers used where oxidisation is eliminated. Yet even still, sets are commonplace.
A set in the blade can be over either plane: as seen down the edge, or as seen down the flat. We can check for hardness with a file, to ‘feel’ the steel.
If it has sabred notably (bends viewed down the flat, veering toward one edge, like a sabre): then we have a couple of choices,
(a)we can keep the blade as such, and correct sabring by regrinding the blade profile and bevels to make it symmetrical again. If we decide to work with it this way we proceed to temper the blade.
Or b) we can discard our hardness and heat the sabred area to critical heat (where it’s semi liquid)and straighten it hot. The start the normalisation and quench processes all over again. Chances are it will do it again. I’ve had to quench some blades up to 7 times pursuing a straight quench.
Ok, so Sabring sucks frankly, you can understand. Our precious baby got busted up.
Then there’s the less hair pulling type of bend, a simple ‘set’, or four, as viewed down the edge of the blade. We’re not going to sacrifice our hardness by requenching (and risk sabring) over a few sets in this plane.
To fix these, we proceed to temper, and after an hour at one’s favoured tempering heat we whisk the blade out and straighten these sets at 250C odd. At this temp sets come out easier, but not always easy.
Often I won’t get all the sets out after one tempering if it has multiple sets, I’ll put it back in the kiln for it’s second cycle of one hour. Then hopefully I can get the rest out on the second try.
Swordmaker flex testing – After the first temper I’ll flex the blade to around 25 degrees or so to check that the blade isn’t soft. If it’s soft it will show. I’ll feel it. After straightening and the second temper I’ll cool the blade and flex test it again to 25 degrees or so each way. The blade will return to straight now. Provided it has no soft untempered areas (which may send me back to the start). Ok so my controlled flex tests will show if a blade is hardened, and where the sets may be remembered in the steel.
Some sets, especially in the strong of the blade (the thicker area nearer the shoulder)can be super hard to get out. For these I’m not strong enough to do it by hand, and may use a vice or press to crank in massive counter-flexes of up to 90 degrees, at 250C, to try to convince the set to come out, and the blade to sit straight. Sometimes the set still says no and I’ll have to get tough with it. I’ll heat that area again with a torch to purple/ blue heat (270C) and then crank it to 90 degrees maybe splash it with some cold water to shock freeze it, maybe leave it in the vice to cool and get a new ‘memory’ overnight. That’s for one set. Often we need to deal with several. And with a well tempered blade, those sets don’t want to come out. We need to fight them into submission and get them to stay there.
Ok, finally through a bunch of tempering heats and elbow clicking we have our blade straight at last. Even then they don’t want to stay on the straight and narrow. I mean what in nature does. It takes strict discipline to keep your kids, dogs, etc. ship shape – they want to do whatever the hell their whimsy feels. Trees don’t grow straight. Water, wind and fire sure aint staying in line for anyone.
Yep our black and crusty blade will take set again - even the repeated rubbing of the molecules and low heat generated in hand sanding with paper on a cork block (let alone a belt sander) can set the blade off again. Just the process of taking off that forge blackening and making it look like steel again, our esteemed swordmakers are back to pushing semprini up hill.
We can’t heat the blade again we’ll lose our satin sheen. I’ll often set the bend(s) by laying it down over two blocks of wood, set apart with the set suspended between, and then standing, nay, bouncing down onto the set point. These things are strong, and I’m not featherweight – me bouncing down and pushing down on a supporting wall at the same time, onto a set, I’m probably applying around 300kg of force. They’re very bloody well heat treated, but being straight as a pin for a metre is just NOT a natural condition for a metre long piece of thin leaf spring.
Ok so I’m building a picture. Blades naturally come out of the quench bent. We straighten them. The Client gets a straight blade which has excellent heat treatment. But that doesn’t mean the blade wants to be straight. It’s straight because we put it there.
I will condition this story by saying once in a while there will be an inherently straight blade emerge from quenching. I’ve encountered a handful or two. But they are almost without exception under 32” in blade length. The shorter the blade the more common it occurs. And they are the exception, not the rule.
If a blade only had one set or curvature in it from quenching: In most cases I can flex it hard as hell in one direction and it will return no further than straight. But a purposeful flex in the opposite direction will ‘remind’ it that it likes setting that way. That in no way reflects the quality of the steel structure or heat treatment. And in normal use it’d be happy to stay straight. It’s just that the steel has a memory which can be set off when flexing beyond the normal parameters of an everyday cut. Luckily a single set blade can just be flexed hard in the opposite direction to set it straight. I’ll usually isolate the fine/ thin tip area by holding it flat on a bench with a gloved hand, while pushing up at the forte with another. Using the palm heel of my flat hand to put extra pressure in the location of any set.
If a blade has several sets in it from quenching, left right left etc. Then the flex test will set a selection of those off, and each needs to be isolated to correct them. So unless the client wants to be clicking their elbows or bouncing on the set suspended on two chunks of wood, then they’d best avoid their flex tests and just use the blade as a blade.
Ok, so that’s the nuts and bolts of what’s happening under the hood. The frozen collection of various molecules in steel has a ‘memory’. They will stay straight until heat or force sets them off. So please just treat your blade well, and use it as intended, and it will love you long time.
What happens when a user ‘flex tests’ their blade:
Firstly they lack the feel and control developed by their sword maker to know what they are looking, nay, feeling for. They even may blindly try to imitate extreme (sensational) tests they’ve seen online, in mockingbird fashion. This is when Johnny has a bad day.
And so I conclude that flex testing by most users as presented in the mainstream sword media is BUNKUM… pervasively misunderstood, unneeded, and misapplied,
BUT it may have a small place at the hands of an experienced, discerning, and mature collector. And flex testing certainly has a place in the hands of your friendly neighbourhood sword smith.
To the general swordbuying who want to better know their blade I say: ”‘Feel’ various steels (mild steel, tools teels, drill bits, stainless knife blades, wallhangers etc), with delicate hands, using a smooth file. Build up your understanding of the different feels and you’ll soon be able to detect a blade’s hardness and easily sand out any marring. Or using good form and edge alignment, test your sword, and yourself, by doing what it’s meant to do; Cut Stuff Up!”
Respectfully
Brendan Olszowy
I want to bring something up. I feel the public have been misled. And it's a misunderstanding propagated by certain 'authorities' on swords, certainly the free online media, and propped up by some misguided advertising on the part of certain manufacturers. It's another 'fad' in the sword communities upon which I, via my experiences over the last 8 years, stand in disagreement.
And I want to bring it out of the proverbial darkness of sensationalism and hype and layman’s gospel into the light of the reality in which I live.
I'd like to hear other swordmakers, like Jeffrey, Lukas, Seth et al. come out with their supportive or non-supportive experiences too. And comments by the ommunity are welcome.
Let me pre-qualify this by saying that there are obviously people here that know this stuff, perhaps experientially by their own foibles or folly. But the myth is on encountered or misunderstood by most noobs, and its an unhealthily pervasive untruth, or half truth. Some these videos by manufacturers show extreme flex 'testing' without showing the after effects being a sadly bent blade, thought surviving from breakage, which was the intention all along, not the the result be a perfectly straight blade, but these aims not necessarily made clear beyond the spectacle of the bending of the blade.
So after seeing some shocking manufacturer you tube recently, and reading some awful newby naivety on SBG Facebook, I felt compelled to write this...
The Falacy: in a nutshell.... It has been misrepresented to the public that a well hardened and tempered blade wants to be straight, and will withstand strong flexes and return to true.
Whats worse, you've been encouraged that this is a tool available to the general public that you can use to 'test' the temper of your sword.
I disagree, conditionally...
Nota Bene (NB): Before we start, the reader is assumed to have an understanding of heat treatment and it's correct terminology.
*The processes in sum are referred to as Heat Treatment, or HT for short.
*Hardening refers to the quench, a blade at 840 - 890C is rapidly cooled by submersion into a coolant. (Initial temp variance for allow type - low alloy > lower heat, high alloy > higher heats)
*Tempering refers to the release of stressed in a quenched blade via heating to lower temperatures of 200 to 400C depending on the aim of the maker. This can be performed in all manner of methods.
Thats all I want to discuss on that topic.
The Reality:
Ok sword buying public; please understand this is what really goes on. It starts at the quench… nay, it really starts at the foundry… Yep, even foundry steel comes to the maker with a pre-set memory. It’s not visible until one tries to work with the steel. Even cutting blade blanks from flat bar can reveal that the flat bar actually ‘wants’ to sabre. Once I made a cut where one side closed down into the other side so hard that it grabbed my angle grinder fiercely, launching it out of my grip, cutting into my hands I almost lost a finger, but for the joy of plastic surgery and Australia’s great public healthcare system.
Ok, so we’re fighting the memory in the steel to begin with….
Then we sword makers of esteemed patience and craftsmanship make a sword form which is crafted to perfection in every plane. Awesome straightness smoothness and geometry. It's great, we pour out our talent and patience through magical hands, forging, grinding, drawfiling this steel into an ostensibly perfect blade form. But then, sadly, we have to turn our fine creation over to the elements, by heating it into a plastic, semi liquid state, and then snap freeze this long and complex shape, causing all sorts of variety of stresses inside the blade at a mollecular level.
Now, providing we’re in luck we have good molecule structure transformation (i.e. hardening) and our sword is not a pretzel and didn’t crack. I’ve never had a blade crack in quenching, but they almost without exception will take a variety of sets. Blades set, sabre, and crack because the process of molecule transformation is not uniform over the length nor breadth of the blade. Expensive and elaborate technologies have been developed to try to eliminate variables and try to make for the most uniform transformations possible. But this high tech equipment is beyond the access of all but a few swordmakers. These may include the use of salt baths, rather than forges, furnaces, or kilns for heating. There are even vacuum chambers used where oxidisation is eliminated. Yet even still, sets are commonplace.
A set in the blade can be over either plane: as seen down the edge, or as seen down the flat. We can check for hardness with a file, to ‘feel’ the steel.
If it has sabred notably (bends viewed down the flat, veering toward one edge, like a sabre): then we have a couple of choices,
(a)we can keep the blade as such, and correct sabring by regrinding the blade profile and bevels to make it symmetrical again. If we decide to work with it this way we proceed to temper the blade.
Or b) we can discard our hardness and heat the sabred area to critical heat (where it’s semi liquid)and straighten it hot. The start the normalisation and quench processes all over again. Chances are it will do it again. I’ve had to quench some blades up to 7 times pursuing a straight quench.
Ok, so Sabring sucks frankly, you can understand. Our precious baby got busted up.
Then there’s the less hair pulling type of bend, a simple ‘set’, or four, as viewed down the edge of the blade. We’re not going to sacrifice our hardness by requenching (and risk sabring) over a few sets in this plane.
To fix these, we proceed to temper, and after an hour at one’s favoured tempering heat we whisk the blade out and straighten these sets at 250C odd. At this temp sets come out easier, but not always easy.
Often I won’t get all the sets out after one tempering if it has multiple sets, I’ll put it back in the kiln for it’s second cycle of one hour. Then hopefully I can get the rest out on the second try.
Swordmaker flex testing – After the first temper I’ll flex the blade to around 25 degrees or so to check that the blade isn’t soft. If it’s soft it will show. I’ll feel it. After straightening and the second temper I’ll cool the blade and flex test it again to 25 degrees or so each way. The blade will return to straight now. Provided it has no soft untempered areas (which may send me back to the start). Ok so my controlled flex tests will show if a blade is hardened, and where the sets may be remembered in the steel.
Some sets, especially in the strong of the blade (the thicker area nearer the shoulder)can be super hard to get out. For these I’m not strong enough to do it by hand, and may use a vice or press to crank in massive counter-flexes of up to 90 degrees, at 250C, to try to convince the set to come out, and the blade to sit straight. Sometimes the set still says no and I’ll have to get tough with it. I’ll heat that area again with a torch to purple/ blue heat (270C) and then crank it to 90 degrees maybe splash it with some cold water to shock freeze it, maybe leave it in the vice to cool and get a new ‘memory’ overnight. That’s for one set. Often we need to deal with several. And with a well tempered blade, those sets don’t want to come out. We need to fight them into submission and get them to stay there.
Ok, finally through a bunch of tempering heats and elbow clicking we have our blade straight at last. Even then they don’t want to stay on the straight and narrow. I mean what in nature does. It takes strict discipline to keep your kids, dogs, etc. ship shape – they want to do whatever the hell their whimsy feels. Trees don’t grow straight. Water, wind and fire sure aint staying in line for anyone.
Yep our black and crusty blade will take set again - even the repeated rubbing of the molecules and low heat generated in hand sanding with paper on a cork block (let alone a belt sander) can set the blade off again. Just the process of taking off that forge blackening and making it look like steel again, our esteemed swordmakers are back to pushing semprini up hill.
We can’t heat the blade again we’ll lose our satin sheen. I’ll often set the bend(s) by laying it down over two blocks of wood, set apart with the set suspended between, and then standing, nay, bouncing down onto the set point. These things are strong, and I’m not featherweight – me bouncing down and pushing down on a supporting wall at the same time, onto a set, I’m probably applying around 300kg of force. They’re very bloody well heat treated, but being straight as a pin for a metre is just NOT a natural condition for a metre long piece of thin leaf spring.
Ok so I’m building a picture. Blades naturally come out of the quench bent. We straighten them. The Client gets a straight blade which has excellent heat treatment. But that doesn’t mean the blade wants to be straight. It’s straight because we put it there.
I will condition this story by saying once in a while there will be an inherently straight blade emerge from quenching. I’ve encountered a handful or two. But they are almost without exception under 32” in blade length. The shorter the blade the more common it occurs. And they are the exception, not the rule.
If a blade only had one set or curvature in it from quenching: In most cases I can flex it hard as hell in one direction and it will return no further than straight. But a purposeful flex in the opposite direction will ‘remind’ it that it likes setting that way. That in no way reflects the quality of the steel structure or heat treatment. And in normal use it’d be happy to stay straight. It’s just that the steel has a memory which can be set off when flexing beyond the normal parameters of an everyday cut. Luckily a single set blade can just be flexed hard in the opposite direction to set it straight. I’ll usually isolate the fine/ thin tip area by holding it flat on a bench with a gloved hand, while pushing up at the forte with another. Using the palm heel of my flat hand to put extra pressure in the location of any set.
If a blade has several sets in it from quenching, left right left etc. Then the flex test will set a selection of those off, and each needs to be isolated to correct them. So unless the client wants to be clicking their elbows or bouncing on the set suspended on two chunks of wood, then they’d best avoid their flex tests and just use the blade as a blade.
Ok, so that’s the nuts and bolts of what’s happening under the hood. The frozen collection of various molecules in steel has a ‘memory’. They will stay straight until heat or force sets them off. So please just treat your blade well, and use it as intended, and it will love you long time.
What happens when a user ‘flex tests’ their blade:
Firstly they lack the feel and control developed by their sword maker to know what they are looking, nay, feeling for. They even may blindly try to imitate extreme (sensational) tests they’ve seen online, in mockingbird fashion. This is when Johnny has a bad day.
And so I conclude that flex testing by most users as presented in the mainstream sword media is BUNKUM… pervasively misunderstood, unneeded, and misapplied,
BUT it may have a small place at the hands of an experienced, discerning, and mature collector. And flex testing certainly has a place in the hands of your friendly neighbourhood sword smith.
To the general swordbuying who want to better know their blade I say: ”‘Feel’ various steels (mild steel, tools teels, drill bits, stainless knife blades, wallhangers etc), with delicate hands, using a smooth file. Build up your understanding of the different feels and you’ll soon be able to detect a blade’s hardness and easily sand out any marring. Or using good form and edge alignment, test your sword, and yourself, by doing what it’s meant to do; Cut Stuff Up!”
Respectfully
Brendan Olszowy