Hello,

I am somewhere in the middle of putting together a plate harness that is entirely made out of heat-treated and tempered spring steel, but being inexperienced with metallurgy I am now at a cross road regarding appropriate material thickness. I'll try to be as brief as possible..

The next step will be to acquire either a helmet or a breast plate (hopefully both at the same time!) and, looking at what historical sources I can find, the thickness of these components could be upwards of 3mm in certain places (over the crest of the helmet and/or the very center of the chest, for instance), which is quite substantial. Now, given that the main advantage of modern spring steels is their strength/thickness ratio, what would be a suitable thickness for my pieces? I'll add that the stock choices are 1mm, 1,5mm or 2mm. The overall production cost will rise in accordance with the thickness I choose, but I would like to find a good balance between the weight and the protection given so as to get the most out of my decision.

I am not currently involved in any reenactment or sparring so the armour is unlikely to face any damage at this point, but I am operating out of a theoretical "what if"-perspective. A supremely light harness would probably feel and handle like dream, but I would not like to compromise the defensive qualities completely for that. I am aware that the specific attributes of spring steel can vary from sample to sample but, in general, how would a piece of armour made out of hardened spring steel stand up versus thicker untreated steel plate? Say +33-50%?

I hope that this isn't an inept question to ask, seeing as I'm surely missing a lot of details, but I would love to be able to find some knowledgeable advice to help me come to a decision that'll leave me happy.

Thanks for reading, and please let me know if there's an important angle that I've yet to touch on. ;)
//Emil Andersson

I guess that the helmet you're getting are two halves welded together? If so, the crest will be thicker than 3mm. ;)

But I'd suggest going for similar (average) thickness (= weight) rather than similar average strength. The metal used in armour probably varied considerably over time and between individual pieces, and might be close to modern spring steel in strength, or not. I think that near the end of the middle ages, the better armours were made of a version of spring steel.

Anyway, for historical accuracy, I think that weight is the most important characteristic.

For fighting on foot, the stock choices are the most you will ever need. 1.5mm would be fine on the breastplate, 1mm on the limbs. Jousting on horseback, different story. Reinforcing pieces could take care of that, though!

Thanks for your input, guys.

@James, thank you for reminding me of that little detail - I definately intend to use the harness on foot. I tend to forget that when accounts of historical knightly armours are made, being mounted on a horse is often factored into the equation. :)

@Paul, I'm actually not sure how the armourers will go about creating the helmet, but welding two pieces together sounds like a possibility.

I'm currently waiting for a reply on a question I sent them where I asked if they'd be able to create armour plates of varying thickness instead of having it static throughout the entire piece, and how that would affect the price. Asking for a breast plate that's made out of nothing but 2mm thick heat-treated spring steel would cost me something gross, but one of gradual thickness (say, from 2mm down to 1mm on the sides) sounds fanciful. The placing of my order is not due until June anyway, so I've got time to think and ponder. :)

Thanks again,
Emil Andersson

Hello again,

I have a follow-up question that bears some relevance to the original topic, specifically when it comes to fighting on foot - I noticed in the "show your harness!" thread in the historical section that one forumite had purchased a breast plate that was made for use on foot, and it had only a very short fauld that ended just below his midsection. In contrast to this, would a breast plate with a fauld and tassets long enough to help protect the thighs not be as well suited for combat on foot? I suppose that a longer fauld and tassets could be in the way if you were to bend forward too far or if you were trying to crouch, although I don't have any practical experience at all here, really..

For reference, this is the breast plate that I am eyeing for my future order:
http://www.bestarmour.com/breastplate/breastplate_10a.jpg
http://www.bestarmour.com/breastplate/breastplate_10b.jpg
http://www.bestarmour.com/breastplate/breastplate_10c.jpg

The images are watermarked, in case you were wondering about the inconsistent trace image on top of the armour. :)

I have been experimenting with hardened steel for armor for a while and here is what I think of it.

Properly hardened steel is roughly as difficult to dent as mild steel that is twice as thick. However while mild steel can be straightened tens of times, hardened spring steel cannot, it will simply crack. Also to some extent hardened steel bends as easily as unhardened, it simply returns to its original shape while mild steel stays bent. So you would not want to make armor twice as thin as you would make of mild steel.

Overall 1.5 mm should be enough for cuirass. If back plate was made of multiple pieces I wold probably make middle ones of 1mm steel, should be enough unless you expect to be hit in the back with maces and pollaxes. I would leave waist and upper part 1.5 mm because these parts get most stress. However if you have large pauldrons that cover most of the upper back you could order a back plate with only the waist part made of 1.5 mm steel. You could order breastplate made of 2 mm steel, or in case of gothic/milanese style lower piece made of 2 mm steel and upper piece made of 1.5 mm steel. Would be more historically accurate. 2mm hardened steel would protect you from most handguns, by the way ;-)

For fauld I would use 1-1.5 mm (probably 1.5 mm for the whole front or upper couple of lames and 1mm for the rest), same thickness for tassets. Depends on how hard you expect to be hit and how durable you want your harness to be. In real battle I would prefer lighter armor as long as I can make it through the fight alive and without serious injuries. By the way, I fight in cuirass with relatively long fauld and large tassets and it causes no problems with mobility.

While 1.5 mm is enough for helmet, I would order helmet with dome made of 2 mm and the rest made of 1.5 mm. Extra weight saves you brain trauma, and it would still be historically accurate. Also for such "domed" parts as helmets and knee and elbow cops actual thickness depends on the manufacturing technique (dishing, raising, welding multiple pieces together and combination of these methods) and will most certainly be smaller than the stock material, so ordering them thicker is reasonable.

For arms I would use 1mm for everything except pauldron plates that protect shoulder joint (these get hit most often), elbow cops (the "domed" pieces) and knuckle plates on gauntlets (if there are any).

For legs 1mm is enough for greaves, but upper leg and knee get hit very often and hard, so 1.5 mm is a way to go if you want to fight hard. However 1 mm would probably be more historically accurate.

And last, there are different steels and they can be hardened using different technologies. I have seen 0.9 mm hardened steel (bandsaw) which was extremely difficult to bend by hand, let alone to break, so springy it was. And I have seen 1.5 mm steel that could be broken relatively easily. So "hardened spring steel" tells you about as much as "battle ready sword". It can be excellent, but it can be awful as well. You will probably get something in the middle.

Something to think about is whether the armour is to protect just you, or itself as well. Historically armour was simply to protect the wearer, and damage was expected, so the plates were only as thick as needed for that. I have handled a c.1580 full harness for an average sized man which weighed probably 45 pounds and many of the pieces (arms for example) were only about 1mm thick.

The thickest part of my own jousting harness is the breastplate, at 1.6mm thick, and it has no damage from lance hits (I compete in balsa-tip jousting, but still get hit by the body of the lance occassionally). Armour made thick enough to protect itself from dents is heavier than it needs to be for its primary job, which is to protect you from damage. I am tall (1.90 meters or 6'3") and my c.1400 full harness has about 60 pounds of steel in it; it could probably have been lighter if I had been more adventurous with the steel thicknesses.

The type of steel and the heat treatment is what it is all about. Too hard is brittle and will crack rather than deform, too soft and you aren't getting the full benefit of using carbon steel. My own harness is made of 1050; I have heard from an armourer who does spring steel harness, that 1070 is more prone to cracks as it builds up more stress even though its theoretical strength is higher than 1050.

1050 is very forgiving. It can be cold-worked relatively easily, even after quenching it is not super-hard, it is also forgiving during quench yet it gets harder than armor should be so after tempering it gets just correct hardness and toughness. 1070 will not be much tougher because it is also plain carbon steel and carbon content difference is not that big. You can make it harder, but you don't need hardness, you need toughness. Maybe it can be a little tougher, but it is much more difficult to work with, it is prone to cracking when cold-worked and it is less forgiving during quench. So a lot of trouble for little if any gain. Now if you need a real increase of toughness you need an alloy spring steel, something with manganese and/or silicon. However these steels may be a pain in the back to work with and thin sheets made of such steels are very rare.

Thank you for sharing your experiences with me. I think I'll be going with a 1,5mm breastplate, and a helmet where the dome is 2mm and the rest of it 1,5mm. I'm not knowledgeable enough to estimate the quality of BestArmour's tempered spring steel, but the few practical tests I've made with my gauntlets and sabatons (both 1mm thick) have shown that they hold up well to harsh blows, without any visible structural damage.

I'm still very much open to input, though. :)