Blacksmithing
and Cutlery
by Gérard HEUTTE
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Steel and its use
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No possibility of making cutlery without speaking about steel. This page gives basic concepts
on steel and its use.
Matter
Steel is a Carbon and Iron alloy.
Its qualities are numerous:
- It can be worked cold (machining, abrasion).
- It can be worked hot (forging, stamping).
- Its mechanical properties (hardness, strength) can be modified by heat treating of which
most known is "hardening".
- Reasonable price.
The steels used in cutlery contain between 0.5 and 2% of Carbon.
Below 0.5%, one speaks about mild steel. This type of steel hardens poorly.
Beyond 2%, one speaks about cast iron which is a breakable matter.
Chemical elements can be added to the steel to modify its properties. One speaks then
of steel alloy. Nonallied steels are called "carbon steel". Which is a pleonasm
since all steels contain Carbon. It should be understood like "only Carbon".
Which steel to start?
To start in cutlery, a simple and efficent steel should be used. One of most known is
the XC70. It is a Carbon steel, with 0.70% of Carbon. It is easy to work and enables
to create good blades.
Close nuances as XC65 or XC75 can be used.
When supplied, steel is generally delivered in the annealed state (not hardened).
It is then a bit harder than "scrap iron" and can be easily sawn, drilled or filed.
Where to buy some steel?
Scrap Steel must be avoided. Indeed, except special case, the steel reference is not known... The
temperatures for working and hardening are unknown. In this case, how to work correctly?
The only way is to run a serial of tests to find the best choices. This method is interesting only
if a big quantity is available because it requires many tests. Furthermore, it requires some
experience.
The steel in the DIY stores is not adapted to cutlery: It is construction steel ou soft steel. It
cannot be hardened (not enough carbon)!
The only possible use for these steels is to use it to learn forging, to avoid
wasting "good steel". So, no knife and no heat treating !
The best solution is to buy a steel with a known reference and get (through the supplier or on the web)
the datasheet for this steel. The price is not a real problem. A bar of 1m in 26x3 section costs less
than 10 euros. There is enough steel to make 6 to 8 folder's blades...
Use and work of steel
Making a blade will utilize various operations impossible to circumvent. Here are
the principal ones:
Cutting out: Annealed steel can be
easily cut out with simple tools as the saw, the angle grinder.
Forge: This operation is a
hot deformation of the matter by hammering. As an indication,
this operation is carried out from 750 to 950 °C. The range of adequate temperature
varies according to steel used.
Abrasion: On annealed steel,
abrasion can be done with abrasive paper, files, a grinder, a angle
grinder, backstand... On the hardened steel, it will be better to avoid files. Furthermore,
it is necessary to avoid overheating at the risk of removing the hardening.
Annealing: This heat
treatment consists in heating steel then to let it cool slowing. There
are several types of annealing. Most known is the annealing of
relaxation. It enables to reduce the internal
tensions following the work of steel.
Hardening: This heat treatment
consists in heating the steel until it becomes "red", then cool it
quickly in water or oil. This treatment makes possible to
harden steel, but makes it breakable.
Tempering: This heat treatment
follows hardening. It is necessary to heat the blade towards
200 °C, to maintain it some time and to let it cool. After this operation, steel have
lost a little hardness but enormously gained in strength. One can carry out this operation in
a domestic oven.
Polishing: This operation
improves the surface quality of steel. Polishing can be
manually made with paper, sandpaper, stones or via machines.
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