Cast Iron or Granite.
Both hold accuracy. The measurement task decides between them: higher-accuracy work typically calls for granite, and where the two cross over, preference decides.
Cast Iron
Granite
Standard
DIN 876-2
DIN 876-1
Finish
Hand scraped, fine milled or ground
Precision lapped
Largest single piece
10,000 × 3,000 mm
To 10,000 mm in length; width a function of length
Work holding
Ferromagnetic — supports magnetic clamping
Non-magnetic — suits magnetically sensitive inspection
Thermal behaviour
Conducts and equalises temperature quickly
Low conductivity; gradual, even response
Interface features
Machined directly into the casting
Cast iron or stainless steel elements bonded into the granite
Specify cast iron
Heavy fixture-loaded work, workshop floor conditions, and anywhere features are machined directly into the surface.
Specify granite
Temperature-controlled inspection, non-magnetic requirements, and environments involving coolant or solvent.
Many inspection departments hold both, with cast iron on the workshop floor and granite in the standards room.
Deciding between the two?
Material selection is confirmed from the accuracy and environment.