39.) In order to reduce to a minimum the friction due to the lateral pressure of the plate against the bearings of the slot, the apparatus is sometimes placed upon several parallel steel rods to form a roller base.

A slight initial load is applied to take up the lost motion of the machinery, and the beam balanced.
[Illustration: FIG.

39 .-- Making a shearing test.] _Log of the test_: The load is applied continuously and at a uniform rate until failure, but no deformations are measured.
The points noted are the maximum load and the length of time required to reach it.

Sketches are made of the failure.

If the failure is not pure shear the test is culled.
The shearing strength per square inch is found by dividing the { P } maximum load by the cross-sectional area.