The
simplest, most precise
and utterly useless answer is
engineering. A sword has to be properly designed for its intended
use. If that use is simply to hang above the mantle and look
pretty engineering barely matters. If the intended use of that
sword is to replicate or exceed the performance of the originals it is
vitally important. If you are looking for a wall-hanger you don't
need to read this- all you need are eyes and money. Assuming that
you want a sword that can actually be used without it self- destructing
or injuring you in the process, you want a well-engineered sword.
But what exactly does that mean? A lot of factors go into good
engineering in a sword. Here are the things you should consider:
Steel
The start
of any good sword
is the steel. A wide variety of
steels will make a good sword. The basic requirement is for a medium to
high carbon steel. Stainless steels are not ideal for a sword, as
cutlery quality stainless steels do not resist shock well enough.
Stainless steels should only be considered if low maintenance is a
higher priority than long term use-ability. Some steels
that have been used very successfully for European swords are 5160, L6,
CK55, 1065-1095 tool steels. There are some newer high-alloy tool
and cutlery steels that should also work well, but I am much less
familiar with them. Beware of claims of 'magic' steels as
well. Far be it from me to say there's no magic in the world- but
science is provable and pretty reliable.
Pattern
welded steels (that
we currently refer to as 'Damascus' steel)
can be very good for swords -or very bad. Good Damascus is
good steel, but it should be bought for its craft and artistry.
It is unlikely to be superior to modern steels in performance, and
frankly there aren't too many of us that would risk a valuable art
piece in hard-core performance testing. There are too many other
variables to spend the extra for some notion that it will out-perform
modern alloys.
People
marketing swords say
all kinds of things about the steel they
use. There are some things said that you should look out for- not
the least because they don't say enough. There is a company
making swords that specifies only 'High Carbon steel.' What they
don't tell you that the steel has not been hardened and tempered.
There are other companies that say 'spring steel.' This is not
very informative- 4130 is a 'spring steel' that isn't suitable for
swords. The best manufacturers will not only tell you the type of
steel and that it is tempered- they'll tell you the specifications of
the heat treatment. Most custom makers will tell you about it in
great detail should you so desire. This brings up the next
engineering point-
Heat Treating
This is
simply the process
of making the steel hard and
resilient. A sword blade needs to be hard enough to hold its
edge, but resilient and flexible enough that it doesn't shatter in
use. Heat-treating can be broken down into two parts- Hardening
and Tempering.
To harden
steel you have to
heat it up to a critical temperature called
Solution Temperature. For most sword steels this is between 1400
and 1500 degrees Fahrenheit. At this point the crystal structure
of the steel has dissolved, and when cooled quickly (quenched) it
reforms into a structure called Martensite. This structure is
very, very hard and very brittle. A blade in this state dropped
onto a hard surface can actually shatter like glass. Obviously
this won't make a useful sword without Tempering.
To do
this the sword must be
heated again, though only to a temperature
of a few hundred degrees, and be kept at this temperature long enough
for the heat to 'soak' completely through the steel. This causes
a change in the Martensite that makes it softer but less brittle.
Both of
these processes are
subject to nearly endless variations that
produce different results. The hardness of steel for knives and
swords is expressed in terms of Hardness Rockwell C (HRc, HC or
Rc.) Typically modern swords are through-tempered, i.e. the same
hardness all the way through. These swords ideally range between
HRc50 to HRc54. This usually provides good compromise hardness
for edge retention, shock resistance and flexibility.
Some swords are selectively hardened like Japanese swords- these will
be around HRc56-60 at the cutting edge, but the spine of the blade will
be quite soft. This isn't ideal for European style swords, as
they can bend if the blow is a little off when striking a target.
A third method (which I use) is called differential tempering.
The whole blade is brought to a temper that is quite high for a sword
blade (HRc58-60) and then selected areas of the sword, the spine and
tang, are tempered to a lower hardness (HRc45-48) leaving the cutting
edges at the higher hardness. This technique provides excellent
edge retention and flexibility. It is not suitable for all
swords- some swords are too narrow for this technique to be applied.
Some
makers leave the tang
soft with the steel not hardened at all-
this has occasionally resulted in swords bending at the join of the
tang and the blade. I don't recommend it- I prefer that the tang
be hardened and then tempered to HRc45-48. It is interesting to
note that many medieval swords had the tang and first couple of inches
of the base of the blade made out of softer steel or iron and scarf
welbed to the blade- this practice persisted into the Early Modern
Age. If it worked for them it ought to work for us though I am
not sure that any maker of quality modern swords uses this method.
The best
steel and tempering
in the world isn't enough to make a good
sword, however. There are many other considerations, such as:
Balance and
'Harmonic' or ‘Dynamic’ Balance (See Article for more
detailed information)
Balance
is often thought of
as locating the sword's Center of Gravity
(COG) correctly. What determines what is correct can get really
complicated. Medieval swords balance the way they do because they
have to balance that way to work correctly. An improperly
balanced sword will transmit shock into the hilt where you grip the
handle. Not only can this make the sword unpleasant to use; it
can actually split the handle or damage the join of the tang and blade
or tang and pommel. In one extreme case I saw a handle actually
burst apart in the users hand when a heavy blow was struck.
Ideally you should feel no shock where the sword is gripped (under the
index finger and thumb for a one-hand sword, or under the middle and
ring fingers for a hand-and-a-half or two-handed sword) when striking a
target, even if the blow lands wrong. We call this 'Harmonic
Balance' or 'Dynamic Balance.'
The
importance of Dynamic or
Harmonic balance cannot be underestimated-
even if everything else is right, I would be hard pressed to call a
sword 'good' if this quality is absent.
Distal and
Profile taper
Most
antique medieval swords
had some greater or lesser degree of
distal taper- they taper in thickness from the base of the blade
towards the point. The amount of taper can vary from as little as
20% taper to as much as 60% or even more. Some medieval blades
were less than a sixteenth of an inch thick immediately behind the
point. This can be a critical factor in properly balancing the
sword. Also important is profile taper- though the amount of
profile taper varies according the swords intended use. Medieval
swords normal range of thickness at the base of the blade was between
3/16 and 3/8 of an inch, with varying degrees of distal taper.
Tapers aid in balancing the blade by progressively lightening it
towards the point. This means that a smaller pommel can be used,
and helps decrease the overall weight of the sword. It also makes
the blade thinner at the striking point, which means there is less drag
and the sword cuts better. There were swords in various places
and times with little profile or distal taper- to achieve proper
Mechanical or Harmonic balance these blades balance very far down the
blade, and are well suited to heavy slashing blows. These swords
universally have very light hilt assemblies that don't change the
Center of Gravity significantly- blades of this configuration are very
sensitive to small changes in the COG disrupting the Dynamic
Balance. It is worth noting that many 'modern' or 'tactical'
swords with no distal taper and simple handles with bolsters and scales
applied to a full width tang are Harmonically balanced by virtue of the
COG not being significantly shifted by the light hilt assembly.
Generally
swords designed
for slashing or chopping blows will have
little profile taper- some falchions actually get wider towards the
point. Swords designed for cut-and-thrust work will generally
have a fair bit of taper, and swords designed mostly for thrusting (As
Oakeshott's type XV and XVII) will sometimes taper to a needle
point. Some of these swords balance quite close (2-3") to the
guard. An important and often unconsidered effect of profile and
distal tapers is to create a low ‘Polar Moment’ in the sword.
This means that with the greatest percentage of the swords overall mass
concentrated around the center of rotation (the user’s hand) the sword
rotates more easily, making it feel ‘alive’ in the hand.
Hilt Assembly
Medieval
swords were
assembled by passing the tang through the guard,
handle and pommel then peening the top of the tang over the pommel, or
over a bit of metal called a nut, to secure the hilt. This worked
well enough, but in modern times it is difficult to find someone to
tighten it up for you if it loosens and currently other methods are
favored by most makers.
It was
recently and for many
years the practice to thread the tang or
weld threads to the tang and simply screw the pommel on. This was
discovered to be less than ideal, for many reasons.
Asymmetrical pommels like wheel or disc pommels tend to unscrew
themselves due to vibration when the sword is used. Because of
compression or shrinkaghe of the handle material over time it can
become difficult or impossible to have the hilt properly tight and
still have these pommels correctly aligned. These hilts can also
be fragile if threads are cut on too thin a tang, as the whole weight
of the pommel bears entirely on the relatively weak threads. Some
makers have solved this by welding on very thick threads and using
symmetrical pommels like so-called 'scent stopper' shapes. This
works well enough if the welds and fitting are good.
A method
that I used for
years and still occasionally do is to machine
a slot in the pommel for three-quarters or more of the length of the
pommel that provides a tight fit on the tang. I would then drill
through both the pommel and tang, and rivet through from side-to-side
in final assembly. Properly done this provides a tight fit that
will remain tight through years of use. Many makers still use
this method, but it does make it difficult to dismount the hilt should
repairs be needed.
Another
method that works
very well and is used by Angus Trim Swords
and myself is an obscure old method dating to the early 17th
century. Threads are cut on a reduced section of the end of the
tang, usually 1/4-20 for a length of 5/8-3/4 of an inch or so. In
the case of a wheel or other asymmetrical pommel the base is slotted to
prevent the pommel from rotating, then a 1/4-inch hole passes through
the end of the pommel. This hole is countersunk 1/2-5/8 of an
inch to a diameter of 3/8 inch. A 3/8 inch diameter nut
sufficiently long to protrude from the pommel approx. 1/4 inch is then
threaded appropriately and bears on the threads inside the pommel for
1/2-5/8 of an inch. This supports the pommel quite well and has proven
very sturdy in use. Some scent-stopper pommels are drilled round
at the base instead of slotted, as their symmetrical form does not seem
to cause them to rotate and loosen up in use as badly. I drill
the nut through from side-to-side so that a tool such as an ice pick
can be inserted to tighten or loosen the nut. Angus Trim does
not, using instead a hex-keyed nut for use with a 5mm Allen wrench.
Some
things to look out for
in mass produced or custom swords are
welded tangs and rat-tail tangs. There have been problems in the
past with welded tangs breaking due to a poor weld- almost universally
this problem applied to inexpensive imported mass-produced
swords. The rat-tail tang has a very short (3/4 to 2 inches
long) tang with screw thread or rod making up the rest of the length of
the tang. This is a dreadful way of making a tang and is suited
only to wall-hangers, whatever claims the manufacturer might make.
It is a
fairly common
practice to strike the blade of a sword so that
it rings like a bell. It is often used to demonstrate the quality
of the steel, but this is spurious. Any metal blade can produce a
pleasing tone regardless of its quality. What this does
demonstrate is that the hilt is tightly fitted; a European style sword
should ring when struck.
Edge
Geometry
Edge
geometry is important
to cutting ability, whether we are
discussing knives or swords. The angle at which the edges meet to
form the cutting edge is vital to performance. Most swords these
days are a 'Beveled Edge.' This means that the sword’s edge is
flat prior to sharpening, and the edge is then beveled at an angle from
either side to produce the cutting edge. This can work quite well
if the flat is narrow enough. I typically reduce this flat to
4/1000 to 6/1000 of an inch before beveling it to a fully sharp
edge. I find that a thirty-degree bevel works pretty well, being
fairly strong and still very keen.
Another
method is to have
the blades bevels meet directly at the
cutting edge. This can be done by flat grinding the bevels until
the edges meet, or grinding the bevels to a slightly convex cross
section until the edges meet, called a 'Cannel' grind or sometimes an
apple-seed grind or rolled edge. A great many medieval swords
were sharpened in this fashion.
The fully
flat ground edge
offers the best cutting performance as it
offers the least resistance in the cut, but can be fragile. The
'cannel' grind, with the blade bevels being slightly convex offers
excellent cutting power and is less fragile.
Each of
these methods has
advantages and disadvantages. The
beveled edge is strong, but often the flat edge is left too thick
(sometimes up to 3/32 of an inch) before sharpening, resulting in an
edge with too much drag that doesn't cut well. The
flat-ground edge is extremely keen and cuts beautifully, but can
sometimes distort or even chip in heavy cutting. The Cannel grind
is an excellent compromise, but if ground too convex can actually have
more drag then the beveled edge, as well as making the sword too heavy.
Fit
and Finish
This is
placed last because
it's the least important factor. It
is also not exclusively the province of a good sword. I have seen
a number of pieces that wouldn't qualify by this definition as 'good'
swords that had exquisite fit and finish. The point is that a
'good' sword should have all the characteristics listed above and good
fit and finish as well. This basically means that
everything comes together as it should- there are no unsightly gaps or
tool marks and everything is tight. Bear in mind the price of the
item you are buying as well- one should not expect as good a finish
from a production sword sold for $200-$400 as you would expect of a
$1000+ custom sword.