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Aaron Justice
Location: Southern California Joined: 21 Aug 2003
Posts: 183
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 Posted: Sat 12 Jun, 2004 11:06 pm Post subject: Bent blade straightening |
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http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem...eName=WDVW
I might consider bidding on this sword James Aldrich is selling, but because of the bend in the blade I am holding off.
Does anyone know if setting the blade in a vice for a while could straighten it? Of if there is a better way of doing it?
How can there be a perfect sword when PEOPLE come in all shapes and sizes too?
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Scott Byler
Location: New Mexico Joined: 20 Aug 2003
Posts: 209
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| Posted: Sat 12 Jun, 2004 11:22 pm Post subject: |
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Don't know about just using a vise on it... I just usually bend the blade back carefully opposite the bend direction until straight... Whether you'd want to do much of that I can't say (though I expect every time a bend is made the life of the blade is lessened a little...)
There are a couple of blade straightening jigs illustrated on Don Fogg's site. While those would have to be built, I've been doing a 'jig' in a vise simply by taking 3 round dowels, 2 on one side and one on the other, to straighten some stuff with. How it will work on a hardened, and tempered blade, I don't know. Mostly I use it on annealed things. Just put 2 on one side of the vise, put one of the other, and find the center of your bend and tighten down. Let off to see if you've got a straightened blade, and repeat as necessary. And, last but not least.... don't hold me liable if you try this and a blade breaks off or something.... 
The knee makes a good straightening device, too, if used judiciously... 
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Peter Johnsson
Industry Professional
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| Posted: Sun 13 Jun, 2004 7:19 am Post subject: |
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When you need to straighten a blade it is best to use mild heat.
I would advice against cold straightening as it actually means you "beat the blade into submission" untill it is straight. By doing this you could shorten the working life of the blade.
(Note: this applies only to blades with european style heat treat (through-hardened). A Japanese style heat treat (Hard edge-soft body) means the blade can be straightened cold.)
When the blade is heated to a mild heat, it will take a set much more willingly. You will not have to use much force and can ease it slowly into the right shape.Using heat means you need to be very careful not to overheat, especially the edge. But as long as you stay within yellow/yellow-brown tempering color, there should be no problem.
Use a propane burner with a medium/small burner.
Apply the heat like you would paint with a very soft brush: never keep the flame still in one place. Move the flame slowly back and forth over the area you want to straighten. Use the tip of the flame and be careful to avoid "touching" the edges. Lean the flame along the blade or keep it at right angles. Always heat the middle of the blade: the midrib or the fuller. Let the heat soak into the thinner parts from the thicker.
At first nothing seems to happen (and this lasts for a little while) and then all of a sudden heat seems to rise rapidly. Be patient and let time have effect. Slow is best.
!!! Note: As soon as you think you see a slight turning towards yellow it is time to be extra careful !!!
Whenyou reached a yellow/yellow-brown heat (200-230 degrees Celsius) wear a pair of heat resistant welders gloves and use a set of wooden dowels. Slowly ease the blade into shape.
You can rest the flat of the point against a surface and lift the hilt away at an angle while you press down with a dowel at the part you want to straighten.
(Remember that wood will scorch at this tempereature, so do not use your kitchen tabel as support if you mind swordshaped burns in its surface.)
If the bend is S-curved you will have to straighten one curve first and then the other.
If the blade becomes too cold it will not willingly straighten so you will have to reheat after a minute or so (depends on blade thickness). Do not be tempted to overheat. You just have to touch up the heat slightly.
If there are problems in the blade like coarse structure or micro fractures, this is the time when they will present themselves. If this is the case you will likely be the proud owner of a square ended short-sword and an unhilted dagger....Not all that fun. 
But then the blade would have snapped sooner or later anyways and perhaps in a more dangerous situation.
!!! Important: Before you start heating the blade make sure the surface is perfeclty clean and free from fat and fingerprints!!!
Any residues on the surface of the steel will throw the colors and you will risk over heating.
Using heat when straightening is not difficult. (I just use many words here... ) You just have to be careful, not rush the task and think about what you are doing.
It might be a good idea to have a tub or tube of water beside you to be able to make a quick quench if heat should rise above preffered level.
After the blade is straight you can also quickly cool the blade in the water if you like. (you donŽt have to) To my experience it is better to dip the blade in a tub rather than cooling it under running water. You want to cool the blade evenly on both sides, just in case.
Being able to make mild strightening like this is a good skill to learn as it might be considered part of blade maintenance.
Even if a blade is used often in cutting practise, there is hardly any risk it will ever take a set, but should the problem arise, it is good to know how to fix it.
It is like knowing how to polish out minor scratches and restoring the edge: If you use your sword, it is a good idea to know how to take care of it.
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Geoff Wood
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| Posted: Sun 13 Jun, 2004 7:35 am Post subject: |
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Peter
Thanks for the interesting post. Just a couple of questions:
When you are heating the blade, do you do so on the inside of the curve, the outside of the curve or keep flipping it over and do it from both sides?
Do the same rules apply to straightening tangs?
Regards
Geoff
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Peter Johnsson
Industry Professional
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| Posted: Sun 13 Jun, 2004 12:35 pm Post subject: |
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| Geoff Wood wrote: | Peter
Thanks for the interesting post. Just a couple of questions:
When you are heating the blade, do you do so on the inside of the curve, the outside of the curve or keep flipping it over and do it from both sides?
Do the same rules apply to straightening tangs?
Regards
Geoff |
Heat will transfer right through the blade: it is so thin and you heat it up slowly. There should really not be any need to heat both sides. Personally, I still turn it over to make sure I apply the heat evenly, just from habit. I find it is easier ot read the colors this way. You can heat any side you like: inside or outside will make no difference.
The only effect youŽll notice is that the steel might collect condenced water as it heats up to water boiling temperature. This can create a thin (very thin) layer of rust on the side you touch with the flame (if you are using propane). If this happens it will affect tempering color on the side with the oxide. The tempreing colors and the thin oxide is no problem to remove afterwards. You can clean it with vinegar and/or steel wool (or steel wool/fine scotch-brite and oil).
Tangs are usually not hardened, so they will straighten pretty easily. (it is actually easy to overdo the bending; if so, just bend it back)
If the tang is two part construction with a welded on round rod of mild steel making up the part towards the pommel, you have to work with some care. This is a construction that might be fragile and the mild steel rod bends very easily.
If the (base of) the tang *is* hardened, you will have to use heat (and more so than when straightening the blade).
As the tang is short, you might have to use a vice and three iron rods as straightening jig.
This is a simple jig to make: take three lengths of mild steel rod and drill holes through one end. Through the holes put lengths of welding rod. Let the bars hang in the jaws of a vice, two on one side and one on the other. When you close these on each side of the blade/tang you will create powerful pressure causing a localized bend. This is sometimes very handy.
If using this method to straighten a blade you can leave the blade in the vice untill it has cooled down. Do *not* pour water over the blade as it sits in the vice. I have broken a blade once this way. Just let it cool slowly by itself.
If the bend is mild you might be better of just using hand pressure.
The tang and base of the blade is much less sensitive for overheating than is the rest of the blade, of course.
In some cases it might be a good idea to cover the blade base with a wet towel if you plan to do heavy heating of the tang.
If you plan to do heating to glowing heat (for some reason, you do not need this kind of heat for mild straightening) be careful not to overheat the steel as this will cause grain growth, making the steel brittle. Stay within brown-red (very dull red)
I see no reson to apply this kind of heat for mild straightening. More serious straightening should already been done by the maker.
If you do hot peening of the tang rivet, also take care not to overheat (and make sure to stress relieve afterwards) so that the steel does not harden or become brittle.
(note that you may easily scorch the grip if you hot peen without removing the grip first.)
With simple carbon steels (10xx-series) it is also a good idea to stay away from blue heat (higher than yellow/brown: around 300 degrees celsius and above). In the blue range there could be an effect called blue-brittleness. The steel has a good toughness for bending when tempered in this temperature range, but might become somewhat brittle for impact stress. ...We do not want that.
To be safe, it is a good idea to keep tempering to plum-brown/purple or below.
The case of blue-brittleness is a question of some controversy among blade makers. Not all will agree this is a potential problem.
I take the route of "better safe than sorry" and avoid the blue range when tempering.
(Heating untempered/unhardened steel to this temperature have no ill effect. It is just something you might want to avoid with hardened steel)
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Geoff Wood
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| Posted: Sun 13 Jun, 2004 12:50 pm Post subject: |
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Thanks Peter
With that sort of detail even I might have the courage to try it.
Regards
Geoff
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Nathan Robinson
myArmoury Admin
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Patrick Fitzmartin
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| Posted: Sun 13 Jun, 2004 3:39 pm Post subject: |
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Greetings Aaron Justice, I have a Del Tin blade with curve to it. I guess its in the steel. I do not believe you are going to straighten cold. I tried with mine. I am amazed I did not set bend it or break it. It made me see how tough DT blades are. I was not brave enough to play with heat.
Greetings Peter Johnson, Thank you for the detailed input on this. One day I might try this. Sincerely, Patrick Fitzmartin
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Aaron Justice
Location: Southern California Joined: 21 Aug 2003
Posts: 183
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| Posted: Sun 13 Jun, 2004 4:16 pm Post subject: |
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Yeah, great detailed post there Pete. I might be bidding on the blade, but someone on another post says they have an MRL/Del-Tin they might want to sell, and I have owned plenty of viking swords.
Plenty... but there is no such thing as too many...
How can there be a perfect sword when PEOPLE come in all shapes and sizes too?
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This is a standard topic