How is mild steel hardened for tools?

By case hardening with a carbon pack.

Why is mild steel used for hand cut files?

As a substitute for wrought iron.

Carburisation through case hardening.

Using a propane torch or ceramic pot.

The use of mild steel as a substitute for wrought iron in creating hand cut files for the Antikythera Mechanism necessitates case hardening to enhance the file surfaces' hardness.
Leather can be converted into charcoal to serve as a carbon source for case hardening mild steel, using a carbon pack consisting of charcoal powder, salt, flour, and water to transform the metal into high carbon steel through carburisation, enabling the production of durable cutting tools like files.

How is mild steel hardened for tools?
By case hardening with a carbon pack.
What is the carbon source for case hardening?
Charcoal from leather.
Why is mild steel used for hand cut files?
As a substitute for wrought iron.
What process creates high carbon steel from mild steel?
Carburisation through case hardening.
How is leather converted into charcoal for case hardening?
Using a propane torch or ceramic pot.

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Mild steel is used as a substitute for wrought iron in making hand cut files for investigating the Antikythera Mechanism.
Case hardening is employed to harden the file surfaces due to mild steel's insufficient carbon content for quench hardening.
Leather is turned into charcoal using a propane torch or a simple ceramic pot in a fireplace for the carbon source.
A carbon pack made of charcoal powder, salt, flour, and water is applied around the file surfaces for case hardening.
Heating the carbon pack in an airtight environment at a red heat transforms the metal into high carbon steel through carburisation, creating a hard layer suitable for cutting tools like files.