Tuftriding is a process used for steel crankshafts. Since the steel crankshaft is much softer than cast iron, tuftriding was used to harden the
crankshaft journals. Porsche used this process in most of thier engines.
Nitriding and heat treating was also used with steel crankshafts.
Since the Zetec crankshaft is cast iron, it already has sufficiently hard journals.

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