FED-STD-791D
Instead, proceed from step (8) of the sequence for preparation (6.2), and continue
through the complete test sequence (6.3)).
6.3.4 Emergency stop.
Push emergency stop button.
1.
2.
Push instruments button "OFF".
Turn off main electric switch to test cell.
3.
4.
Turn off main water valve to test cell.
Investigate and take appropriate action.
5.
6.4 Inspection and rating.
6.4.1 Scuffed area. The scuffed area of a gear tooth is that area from which the
axial grinding marks have been removed by scratching, scoring, abrasion, and wear. As
shown in Figure 10, areas A and B are scuffed; area C is not scuffed. Note that only the
actual working portion (areas A plus B plus C) of the tooth surface is considered in the
definition of areas.
6.4.2 Percent of tooth area scuffed. The percent of tooth area scuffed is that
portion of the working surface of a gear tooth that has been scuffed. Referring to Figure
10,
scuffed area * 100
A+ B
Percent tooth area scuffed =
=
* 100
working area
A+ B +C
The percent of tooth area scuffed is estimated visually as accurately as possible, but at
least to the nearest 5%, for each individual tooth, with the aid of a net reticule mounted in
the eyepiece of the inspection microscope.
6.4.3 Average percent of tooth area scuffed. The average percent of tooth area
scuffed is the algebraic average of the percent of scuffed area of all 28 teeth of the narrow
test gear. Calculate this value to the nearest 1%.
6.4.4 Effective tooth width. The effective tooth width is the actual width of the
narrow gear tooth that is in contact with the tooth of the wide gear. To determine the
effective tooth width, measure the gross tooth width by means of a micrometer, and
estimate the ratio of effective tooth width to gross tooth width by visual examination or
with the aid of a suitable scale, referring to Figure 10, and 7.1.
6.4.5 Load carrying ability. The load-carrying ability, or the scuff limited load,
of a lubricant is defined as the gear tooth load at which the average per-cent of tooth area
scuffed is 22.5% for the narrow test gear as deter-mined by the method outlined herein.
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