🚀 go-pugleaf

In article <Bs5s0s.843@world.std.com> fhapgood@world.std.com (Fred Hapgood) writes:
>I have been reading in a geology text about something called a
>'Moh scale' that quantifies degrees of mineral hardness.  Apparently
>some gentleman by that name placed ten minerals in order of hardness
>and assigned them the digits 1-10.  This seems primitive.  Is there
>a more comprehensive and precise measure of hardness in use?

The Mohs scale is a measure of the scratch hardness.  Minerals are arranged
in order such that a mineral will scratch another mineral with a lower
number.  Another method of measuring scratch hardness is with jeweled
scratching points.  These use either a set load and measure the width of the
scratch or else they are loaded until a given width of the scratch is
obtained and the load is measured.

Another method of measuring the hardness is the Brinell hardness number where
a hardened sphere is forced into the material under a given load and the
diameter of the indentation is measured.  The Brinell number is

BHN=P/(pi*D/2)*(D-sqrt(D^2-d^2))

where P is the load (kg), D is the diameter of the spherical indenter (mm),
and d is the diameter of the impression (mm).

There are other methods such as Rockwell, and Vickers hardness number.  All
of these should be in any Mechanical Engineering Handbook.


reference: Marks' Standard Handbook for Mechanical Engineers; Baumeister,
Avallone, Baumeister; McGraw-Hill Book Company


Philip Peregino