ported--Load Wear Index (formerly Hertz Mean
Load) and Weld Point. Load Wear Index (LWI)
is a measure of the ability of a lubricant to
prevent wear at applied loads. Weld Point is the
lowest applied Ioacl in Kilograms at which either
the rotating ball seizes and then welds to the
three stationary balls, or at which extreme scor-
ing of the three stationary balls results. It
indicates the point at which the extreme pres-
sure limit of the lubricant is exceeded.
Load) and Weld Point. Load Wear Index (LWI)
is a measure of the ability of a lubricant to
prevent wear at applied loads. Weld Point is the
lowest applied Ioacl in Kilograms at which either
the rotating ball seizes and then welds to the
three stationary balls, or at which extreme scor-
ing of the three stationary balls results. It
indicates the point at which the extreme pres-
sure limit of the lubricant is exceeded.
Apparatus and Materials: The 4-Ball Wear
Tester and the 4-Ball EP Tester are special de-
vices available from laboratory supply houses.
The four steel balls (1/2-inch diameter) in both
tests are of ball-bearing SAE 52100 chrome
alloy steel. For cleaning and preparation of each
apparatus, an Stoddard solvent conforming to
the ASTM D 485 specification, and hexane
conforming to ASTM D 1836 are used.
Tester and the 4-Ball EP Tester are special de-
vices available from laboratory supply houses.
The four steel balls (1/2-inch diameter) in both
tests are of ball-bearing SAE 52100 chrome
alloy steel. For cleaning and preparation of each
apparatus, an Stoddard solvent conforming to
the ASTM D 485 specification, and hexane
conforming to ASTM D 1836 are used.
Modifications of the ASTM Wear Test procedure
have also been introduced, in which bronze balls
have been substituted for the 3 stationary steel
balls, Discs of other materials, held by a special
stationary clamp, have also been used. Wear
measurements of steel-on-bronze, aluminum,
nylon, etc. can thus be determined. These
modifications are not included in the ASTM
method.
have also been introduced, in which bronze balls
have been substituted for the 3 stationary steel
balls, Discs of other materials, held by a special
stationary clamp, have also been used. Wear
measurements of steel-on-bronze, aluminum,
nylon, etc. can thus be determined. These
modifications are not included in the ASTM
method.
A microscope, preferably binocular with mi-
crometer eyepiece, Is required in each test for
measuring scar diameter.
crometer eyepiece, Is required in each test for
measuring scar diameter.
Wear Test Procedure: The steel test balls and
surfaces of the 4-Ball Wear Tester are thor-
oughly cleaned, first with Stoddard solvent, then
with hexane.
surfaces of the 4-Ball Wear Tester are thor-
oughly cleaned, first with Stoddard solvent, then
with hexane.
One of the steel balls is then placed in the chuck
of the Wear Tester. A small amount of the
lubricant is placed in the ball pot of the tester,
and the three remaining balls are placed in the
pot. The balls are locked into position and the
pot is filled with lubricant. The 4-Ball Wear Tes-
ter is then set for operation under the specified
conditions. ASTM suggests 1200 rpm, a 40-kg
load, temperature of 167° F, for a duration of 60
of the Wear Tester. A small amount of the
lubricant is placed in the ball pot of the tester,
and the three remaining balls are placed in the
pot. The balls are locked into position and the
pot is filled with lubricant. The 4-Ball Wear Tes-
ter is then set for operation under the specified
conditions. ASTM suggests 1200 rpm, a 40-kg
load, temperature of 167° F, for a duration of 60
minutes, although tests are often run under
different conditions. Heat Is applied by an ele-
ment within the tester, and then the specified
operating temperature has been reached, the
motor is turned on and rotation begins. At the
end of the test period, the motor is turned off
and the ball pot is removed.
different conditions. Heat Is applied by an ele-
ment within the tester, and then the specified
operating temperature has been reached, the
motor is turned on and rotation begins. At the
end of the test period, the motor is turned off
and the ball pot is removed.
The three stationary balls are washed with
Stoddard solvent and hexane to remove the oil
or grease. Using the microscope, the diameter
of the wear scar on each ball is measured to the
nearest 0.01 mm. Another set of measurements
across each scar, 90 degrees from the first, is
then made. The test conditions, rpm, load, tem-
perature, and time, must also be reported.
Stoddard solvent and hexane to remove the oil
or grease. Using the microscope, the diameter
of the wear scar on each ball is measured to the
nearest 0.01 mm. Another set of measurements
across each scar, 90 degrees from the first, is
then made. The test conditions, rpm, load, tem-
perature, and time, must also be reported.
EP Teat Procedure: Preparation for the 4-Ball
EP Test is similar to that for the Wear test. The
lubricant is first brought to room temperature (80
± 15° F). At a speed of 1770 - 60 rpm, and
under a specified load, the first run begins.
EP Test is similar to that for the Wear test. The
lubricant is first brought to room temperature (80
± 15° F). At a speed of 1770 - 60 rpm, and
under a specified load, the first run begins.
The determination of Load Wear Index in the EP
Test requires 11 runs: 10 of 10 seconds duration
prior to welding, and one run at which welding
occurs. A progressively heavier load is applied
on each run and the scars on the 3 fixed balls
are measured, as above, each time, In testing a
lubricant of unknown EP properties, choice of
the first load is by chance. Therefore, it is
probable that the balls will seize and weld before
10 runs have been completed. Consequently,
after this weld point is reached and recorded,
additional runs at successive loadings below the
weld point are made until 10 sets of scar
measurements without welding have been
obtained.
Test requires 11 runs: 10 of 10 seconds duration
prior to welding, and one run at which welding
occurs. A progressively heavier load is applied
on each run and the scars on the 3 fixed balls
are measured, as above, each time, In testing a
lubricant of unknown EP properties, choice of
the first load is by chance. Therefore, it is
probable that the balls will seize and weld before
10 runs have been completed. Consequently,
after this weld point is reached and recorded,
additional runs at successive loadings below the
weld point are made until 10 sets of scar
measurements without welding have been
obtained.
For each run, the applied weight, multiplied by
the lever arm, is divided by the average of the 6
scar measurements. The resulting quotient is
corrected for the elastic deformation of the ball
surfaces due to static loading. This yields the
"corrected load."
the lever arm, is divided by the average of the 6
scar measurements. The resulting quotient is
corrected for the elastic deformation of the ball
surfaces due to static loading. This yields the
"corrected load."
The Load Wear Index and Weld Point,
described above, are recorded and reported.
described above, are recorded and reported.
A-7 (FIST 2-4 11/90)