AIPD Subcourse No.
0478 ............ Dimensional Measurements
Lesson Objective ..................... Using the learning objectives and
supportive text, you should be able
to state the characteristics check-
ed during the calibration of gage
blocks, the procedure to prepare
gage blocks for calibration and the
equipment used to calibrate gage
blocks. You should also be able
to answer all exercise questions
pertaining to the calibration of
Credit Hours ......................... One
The precision gage blocks now used are of three styles: rectangular,
square with a center hole, and square without a center hole. The blocks are
also classified into grades by the accuracy of measurement attainable with
Three grades you normally come in contact with are AA or
laboratory blocks (primary level); A or laboratory or inspection blocks
(secondary reference); and B or working blocks (secondary transfer).
following characteristics are, checked in the calibration of gage blocks.
Size: how much deviation is there from the size marked on the
Parallelism: how close are the top and bottom to being parallel?
Flatness: how flat are the surfaces used for measuring?
Magnetism: residual magnetism is checked and removed.
Wringability: how free is the block from roughness, scratches,
(1) Clean gage block with gage block cleaner and wipe dry with
lint-free tissue. Use a brush to clean the holes in the square
(2) After blocks are washed in solvent, do not touch them with
your bare hands.
(3) Remove any rust or stains with nonabrasive rust remover.