dispelling Myths about medieval Combat

[Timelord]

Threading was around in the medieval period. It was used on some suits of armour for fixing ablative plates and it has cropped up in other mechanical devices. It was not used for securing sword tangs wielded by the same guys in armour in this period.
I am not in disagreement about keyed on pommels or a pommels limited ability in soaking up part of a shockwave or that the tang should be softer or the radiused shoulders. That is all basic stuff. What I am saying is that the screw threads cut into the end of the tang act as stress raisers at the point of the tang that is subject to the most focus of the shockwave. I have seen tangs shear at this point and the pommels then drop off. Why would you cut an angular grove across the focal point of the tang? Maybe in your experience the modern "super steels" counter this flawed construction method fairly well and that is how you (& some modern manufacturers) can get away with it, but it is still building in a potential structural failure and should not be advised as ok across the board.
What steels are you using for these swords? Does the steel work harden like spring steel or a high carbon steel? as that would be more likely to show up the problem.
It is not about whether a hex nut is as secure as a historical peen. It is about the shockwaves entering an artificially introduced flaw in the metal structure and so then overstressing the crystalline structure at this weak point.
Also having a softer tang (as you should) does not really help to absorb the shockwave as you suggest. The purpose of softening the tang is threefold. 1) So that it is not brittle in the area the shockwaves focus into after travelling down the length of the blade. 2) as most historical swords were made out of steels that would "work harden", then the tang started off soft when the sword was new. this does not alleviate reason 1).
3) So that the peen was soft & "peenable". Otherwise if just softening the immediate area of the peen, then the area immediately in front of the peen would be tempered hard & brittle. Therefore the whole mass of the tang down to and just in front of the shoulders had to be softened. This does not alleviate reasons 1) & 2).
Swords that have seen much use or any from a steel that can work harden (many) are advised to be occasionally "dismounted" and the tangs re-annealed - as many modern swords used in martial arts by enthusiastic participants are subjected to far more and frequent use than their historical counterparts. Regards, TL