9.2 Application of Compressive Force—Assemble the
specimens in the compression device, using extreme care to
place them exactly in the center between the plates to avoid
tilting. If the calibrated spring device (see Fig. 1) is used, apply
the compressive force by tightening the screw until the
deflection as read from the scale is equivalent to that shown on
the calibration curve for the spring corresponding to a force of
1.8 kN (400 lbf). With the external loading device (see Fig. 2),
apply this force to the assembly in the compression machine or
by adding required masses, but in the latter case, take care to
add the mass gradually without shock. Tighten the nuts and
bolts just sufficiently to hold the initial deflections of the
specimen and spring. It is imperative that no additional force
be applied in tightening the bolts