Due to its unique properties, black granite has in recent years been used extensively in the field of measuring instruments, both for traditional ones (surface plates, rules, set squares, etc…), as well as modern ones: three-dimensional measuring machines, physico-chemical process machine tools. Suitably lapped black granite surfaces are not only extremely precise but also ideal for use in conjunction with air bearings. The reasons for the choice of black granite in constructing of precision instruments are the following:
DIMENSIONAL STABILITY:
black granite is a natural aged material formed over millions of years and therefore displays great internal stability.
THERMAL STABILITY:
the coefficient of linear expansion is much lower than for steel or cast iron.
HARDNESS:
comparable to good-quality tempered steel.
DURABILITY: instrument last longer.
ACCURACY:
the regularity of the surfaces is superior to that obtained with traditional materials.
RESISTANCE TO OXIDATION: no corrosion, no maintenance.
COST: with state-of-the-art technology prices are lower.
RECONDITION: Eventual servicing can be carried out quickly and cheaply.
NON-ADHERENCE TO ACIDS, NON-MAGNETIC, ELECTRICAL INSULATOR.
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