Hardness

[burg]

I think there should be a conversion between hardness scales. Rockwell, Vickers, Brinell, Knoop

[bronchole]

I'll second this request.

Probably be a good adea to give it a scale relitive to houshold things also. Like McMaster Carr does on their Rockwell scale:

[kan123]

This is a challenging request. Many of the relationships are only approximate because different methods are used to make the measurements.