How much sword warping is acceptable from PACMET heat treat?

savagesword

savagesword

Joined
Aug 30, 2012
Messages
101
Hello all,

I just received my first batch of swords back from PACMET (Pacific Metalurgical) tempered to 54/56 HRC. There was a little warping ...about 1/8" - 1/4" bow in them.

Is this common with sword blades (36 " length... 5160 steel)?

They said that they clamp them to minimize warping, and do plenty of sword work with local craftsmen.

I'm just curious if this is normal...and I should expect it? Or if there is something I can do to prevent it , etc...?

I thought I would ask the experts here to help understand what to expect?

Thanks for your comments and education!

Here's some profile pics:

heat1.jpg

heat2.jpg
 
With all the stress of milling and grinding - metal warps, long metal warps more. Most HT guys straighten it. Ask them if they normally do such.
 
I just got off the phone with them, and they don't necessarily straighten them (the guy told me that they are just 'processors'..they don't make anything).

He said that the swords will bow during the quench...and then they clamp them for them tempering stage (annealing).. He said they have to compromise the annealing stage to keep the hardening at the proper spec. They don't want to soften it too much and risk the hardening spec. Makes perfect sense.

I am making these swords for collectors that like to know the swords are fully hardened/tempered.. but they're really art pieces for display.

I had these hardened to 54/56 HRC. Is this a reasonable spec for this type of blade?

I'm going to call back at the end of the week to talk with their expert and get more advice on how to keep the blades as straight as possible.
 
Whilst it may not look particularly good from an aesthetic point of view, it is very useful to have a downward bend in the blade for thrusting. All sport fencing blades (Including Sabre) have this downward bend, mainly for safety, but there's also accuracy and resistance to the thrust to consider. Bullfighters blades also have this downward curve. From a safety point of view, if you do get a blade breakage, the broken stump of the blade left in your hand is more likely to go over the opponents shoulder, than bury itself in his guts. From a resistance against thrust POV a blade that bends upwards is more likely to injure your wrist, get pulled from your grip if it sticks in something hard like bone. It's also more difficult to hit a target. Also as the blade loses resistance and penetrates the obstruction, a downward curve creates an aprupt change in force at the wrist, whereas the downward bend allows you to maintain penetrative force without cocking the wrist or changing direction of the thrust.

Striaghtening a blade with the kind of warpage shown on the edge up blades is relatively simple (watch how fencers do it). However, the warpage shown on the left hand blade in the first pic is not easily fixable and shouldn't have got through quality control unless you were after a Keris type blade.
 
A blade of this length will almost always be subject to some amount of warpage, but there are things you can do to minimize it. Leaving the edges around .10 thick and as consistent in thickness as possible over the entire length will help.
IIRC, Tinker Pearce has used PacMet for many years and usually just sends a profiled blank, leaving most of the grinding until after HT. This obviously makes the grinding more difficult and time consuming but my guess is that he does this to minimize warpage and to leave more room to correct it when it does occur.
 
Ahhh.... this is some great advice and comments! Thanks so much.

I thought that this would be pretty normal. I'm learning some good techniques on how to prevent this or fix it after it happens. Thanks a lot!
 
I can't say if it is normal or not for PacMet, but it is an issue with a blade of this length regardless, and it has to be addressed as a foreseeable event rather than a fluke. With 5160 and an out-sourced HT the easiest way to deal with it is probably to leave more meat on the blade before HT to minimize differential cooling rates (thus reducing the chances for warpage), and grind the excess of after HT. With 5160 at 54-56 hrc this isn't as onerous as it sounds, at least in comparison with high alloy steels at higher hardness.
 
You should easily be able to straigten the blades. Search "straighten - warped - knife - blade".
 
I agree with you Stacy. I've done some research and ordered some round-stock to make a vise-based straightening jig. Thanks for all your help! It's always an education!
 
The blade on the far left is designed to be a bit asymmetrical. It is supposed to be an exact replica of the Dungeons and Dragons logo. I enlarged the logo to full size and kept all of the 'asymetric anomalies' intact. So, even though it doesn't look perfect... it really is (to me, anyway):

dndlogo.jpg
 
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