Hi all,

A rather simple, and possibly dumb, question... I have read with much interest the "Sword sharp" thread, about how different blades should have different levels of sharpness depending on their purpose.

Now, I'm wondering about hardness. Nearly all the sword blades I see around the 'net seem to be made with a hardness of cca. 52 to 55 HRc. I was wondering about the correct historical (or "modern functional", too) hardness for other types of blades, notably daggers. I was thinking that maybe a short, triangular-sectioned dagger blade designed specifically to pierce armour would ideally be made with a greater hardness. But I could also be completely wrong (maybe that would mean risking the point to break off easily when impacting armour?).

And what about other weapon types, such as axes, or maces, or spears? I get the fact that ideally, an axe is differentially tempered, but was this always the case, and in the case of a uniformally tempered axe, what would be the historical/ideal hardness? I don't recall reading about differential tempering for spears or maces, anyway.

In the end, is cca. 52-55 HRc always the historical/ideal hardness for any type of weapon, or not?

Thanks in advance,

Cheers,

Simon

Simon,
Hopefully you've already checked out Craig Johnson's great article Sword Blade Hardness: A look at the current research. You can see that, of the period swords tested, 52-55 HRc throughout the blade would be unusual. A modern sword would often be harder than a number of the swords tested and much more consistent in hardness and carbon content across the blade than period examples.

I wish you luck in your quest for answers. As you can see from Craig's article, very few period swords have been tested. It's quite possible there are only a handful of other weapons that have been tested the same as these swords. I haven't seen much, if any, data on anything besides some swords and some armour.

There are some related past threads about how sharp an hard a sword should be, with forum member testing of current production Rockwell C scale hardness. Different people prefer different properties. Some like a Rockwell C ~42 to 45 edge that may roll easier, but to a degree can be gently hammered and worked back out by the owner more easily than say a Rockwell C 52 edge. Also, increasing "springiness" and "toughness" basically trade off against decreasing "hardness" and "stiffness" for most heat treated steel alloys. The same compromises apply to historical swords, which is why I bring this up.

Hi Simon

Big question that is tough to answer in a simple post. In the current market its tough to outline what is acceptable as it is so different for each type of weapon and the intended use by the maker and the actual use applied by the user.

No one design point would give you an answer that would satisfy or even match what is done today. Variations in the type and quality of material, the quality and style of heat treatment and several other factors would touch on these specifications. Today we are able to produce a very consistent result from weapon to weapon but all makers are not striving for the same result or with how one should try to get to a result.

In a very general sense swords need to be in the 50 range for most customers to be happy today. Edges on most other things folks would like hardened. In period most impact weapons where not hardened. This includes a lot of pole arms and other items with edges.

In the case of something like a flanged mace these where not hardened. It would actually make it more prone to not working the way it should.

If you have questions on the article or about specific types of weapons I am happy to add some more but it would be tough to even give a general over view of the subject ion the short space of a post.

Best
Craig

What I am going to write is based 1/3 on logic, 1/3 on my experience and 1/3 on knowledge, so take it with a good portion of salt.

The first thing we need to keep in mind is that in middle ages both materials and work were of very different quality. Just like today. Choose the wrong material, and you will get a dagger/sword/whatever that cannot be hardened. Make a mistake in heat treatment and you get a weapon that is either soft or brittle as glass. The latter thing is always bad, but the former one actually is not. Even soft axe/halberd will cut through cloth and will inflict blunt trauma through maille. You probably don't expect to actually pierce steel plate with your dagger, do you? More likely you want to push it between plates, or tear a single maille link. Soft iron is enough for that job.

So, what was that all about? It was about risk and money. Just as today, people's choices were dictated by how much money they had and how much they were willing to risk. Let's say you have 10 men. You have enough money to buy either 10 bills made of soft iron or 3 pollaxes made of good steel. What would you choose? 10 men with bills of substandard quality are still better than 3 men with good pollaxes, so here you go. Another choice: you are making a dagger. You can harden it, but you don't know if hardening will go well. In other words, you think that the blade may crack during heat treatment or may become too brittle. And you have no means of testing it other than actually try to break it. But if you break it, you will have no dagger. But you can leave the blade soft and it will still make a serviceable weapon. Would you dare to risk, or would you take a safe route?

Now a soft dagger probably is a little bit too extreme. After all in middle ages people could produce knife/dagger blades of acceptable quality quite easily. But from the other hand, during viking age there were blades made entirely of iron that cannot be hardened by heat treatment, so go figure why people were doing them.

From my personal experience 28-30 HRC (unhardened modern tool steel) can make a serviceable short blade (like a bauenwehr). In middle ages such hardness would have objects made of steel that does not have enough carbon or that was poorly heat treated.

35 HRC can make a short sword/messer. This will be quite springy, but in case of thin/narrow blade should be used with care. This is also an OK hardness for a dagger blade, though the point will easily roll if armor plate is hit with it.

40-45 HRC is actually a sping. So a tough blade that holds the edge relatively well yet will rather bend than break. A good choice if you are not very confident in the material or technology you use (though in that case you probably cannot be sure of the hardness as well).

48-52 HRC is modern "standard" for blunt reenactment blades. A good compromise between edge retention and toughness. The blade will rather bend than break.

Above 52 HRC things are starting to get risky. 53-54 HRC will give better edge retention, but will also make a blade that is more likely to break. Such blade should be used with greater care. In modern world you can compare it to a gun that is more accurate and/or shoots farther, but is more prone to jamming when dirt gets inside. 56 HRC is probably too much for a sword, but makes a good knife. Anything above that is way too brittle for a weapon.

But actually things are even more complicated. For example I would probably make a dagger blade with 40-45 HRC but leave the point around 50-55 HRC. I would also make sword edges harder than the center/core of the blade. Also I would make sword tip harder than the base of the blade. So I am not actually limited to modern "standard" for swords. I could have a weapon with better edge retention yet just as tough as modern swords. Or I could have a weapon that is way too soft for most modern users but would be perfectly OK for the job it's intended for.

And finally. Many polearms were actually not hardened. Weapons such as spears, halberds and pollaxes seem not to be affected that much by the low hardness. Even if the point gets dull it is still enough to pierce maille and cloth with a good thrust. Hammers/maces can be soft yet will still deliver as much punch, and all kinds of hooks will still hook well even if made of soft metal. And spikes on maces and flails are there to concentrate force in one spot and not to pierce armor, so these spikes can also be dull.

We know very little about how medieval weapons were made. Two similar weapons could have very different hardness yet would still be considered good. One blade can be harder at the edge than at the fuller and/or harder at the tip than at the base of the blade and/or harder on the surface than at the core. There probably were some "standards" of good weapon, but these were probably more utilitarian. Like a blade was considered good if it could be bent that much and would still return to true. A dagger would be considered good it one could hit an iron plate with it and the point would stay reasonably sharp. But these standards most likely varied greatly depending on period, region and social status. Like for kitchen knives today: european-style knives usually have hardness around 52-54 HRC, cheap ones often even less, while their Japanese counterparts often have edge hardness over 60 HRC.

Excellent thread!

I would like to point out that historical swords and most quality tools would not have one uniform hardness throughout the object, but from either a welded high carbon steel edge on iron swords and axes or from entire steel blades being differentially heat treated, they would be springy or even soft in the core and hard in the edge.
This makes them keep shap and hard while not risking breaking like glass. The edge can crack but the blade doesn't snap easily although it may bend or flex depending on how it was made. Then of course there were some better made and some less so, as well as some made puropsely harder in the edge than the norm and some softer for various reasons. But varying hardness from edge and point to core is a vital, even the most central part of skilled forging of weapons and tools, dating back to the Hetites sometime around 1900 BC.

DIfferential heat treatment isn't a modern invention, nor is it difficult to do with simple tools and a forge. Heat and quench a blade, then polish it to a decent shine and place a lump or bar of red hot iron to the center of it. The metal will change color to yellowish, blueish and even black in stages and as the color reaches the edge you remove the hot iron. This anneals the center and makes it into flexible spring steel while keeping the edge highly tempered and there's no need for modern annealing ovens and high tech gadgets.
In the case of a welded steel edge on iron or low carbon that won't take as much or even any tempering, just quench slower and with more care and you may not even need the anneal.

Modern studies of celtic iron age swords show that they all have at least one welded in steel edge on them. What's hitting the enemy is in effect hard steel for good cutting ability but risks chipping if it's too hard tempered, while the soft iron body of the blade still bends to impact.