Testing Machine, either the hydraulic or the screw
type, with sufficient opening between the upper bearing surface
and the lower bearing surface of the machine for the use of
verifying apparatus. The load applied to the test specimen shall
be indicated with an accuracy of 61.0 %. The load indicating
device shall have a means of indicating maximum load. The
upper bearing shall be a spherically seated, hardened metal
block firmly attached at the center of the upper head of the
machine. The center of the sphere shall lie at the center of the
surface of the block in contact with the specimen. The block
shall be free to tilt in any direction. A hardened metal bearing
block shall be used beneath the specimen to minimize wear of
the lower platen of the machine. The lower bearing block shall
have concentric circles at 1⁄4-in. intervals centered on the block
to facilitate accurate centering of the test specimen. The
bearing block surfaces intended for contact with the specimen
shall have a Rockwell hardness number not less than 60 HRC.
These surfaces shall not depart from plane surfaces by more
than 0.0005 in. (0.013 mm) when the blocks are new and 0.001
in. (0.025 mm) after use.