Surface plate accessories
Granite Surface Plates are manufactured in three grades
◆ Grade AA - Laboratory Grade
This is typically specified for precision operations in constant
temperature gaging rooms and metrology departments.
◆ Grade A – Inspection Grade
This is typically specified for general work in quality control.
◆ Grade B – Toolroom Grade
This is typically specified for production checking work
throughout the shop.
Unilateral Flatness Tolerance
Overall flatness tolerance is based on unilateral measurement.
All points on the work surface shall be contained between two
parallel planes separated at a distance no greater than the
amount specified for each particular grade and size as shown
in our listings.
Repeat Reading Tolerance
Repeat reading tolerance is easily checked with Repeat Reading
Gage. This gage detects local areas, not overall flatness
In addition to the overall flatness tolerance referred to above,
Fortune Machinery provides repeat reading tolerances as follows:
Before shipment, each surface plate must pass a critical final
inspection to prove that its entire surface is within the specified
tolerance. The final inspection is done with an autocollimator in
a controlled atmosphere.
All shipments of precision granite products include a Certificate of Inspection.
Every surface plate in use should be frequently inspected,
especially under shop conditions where abrasion is common. An
effective inspection program should include regular checks with an
autocollimator. If tolerance variations are excessive, the plate can
be transferred to work involving less accuracy or it can be
resurfaced to restore its original level of accuracy.