heat have the same number stamped on them. One important reason for recording the heat number is that
whenever any axle is found to have a manufacturing defect attributed to improper heating and forging, all axles
with the same number can be inspected for the same defect or removed from service. The manufacturer keeps a
record of all axle heat numbers and the consumer who purchased them.
f. Mounting date--Note 8. The date that the wheels are mounted on the axle is given by month and year on
the opposite end of the axle from the date of manufacturer.
g. Point of mounting--Note 9. The place where the wheels are mounted upon the axles is stamped on the
end opposite the place of manufacture. However, both manufacture and mounting may be done at the same
place, and the manufacturer's name or brand may appear on both ends of the axle.
h. Serial number--Note 10. If from any one heat, numerous axles are made, and if the customer specifies it,
each axle is given a serial number. This number is on the opposite end of the axle from the heat number.
2.16. NEW DIMENSIONS
The AAR Wheel and Axle Manual provides the dimensions for axles including standard dimensions for
new axles. The new dimensions for each of the three types of axles are explained in separate subparagraphs.
a. Standard freight car axle (solid-friction bearing). Although most new freight cars being built for
commercial railroads in the United States have axles designed for use with roller bearings, the majority of the
axles used on U.S. military railroads and in foreign countries are the black collar solid axles designed for use
with friction bearings. These axles do not last as long as those designed for roller bearings because the journals
wear more quickly. However, they require less maintenance skill and less exacting inspections. Table II shows
a labeled diagram of this axle along with the new dimensions for it. Notice that the curved surfaces on the
exterior and interior ends of the dust guard collar and the black collar are marked as 1" R or 3/4" R. These
markings establish the curvature of these surfaces by defining the radius of the curve they would make if the
complete circumference was drawn. For example, the interior curved surface of the black collar is marked 1" R.
If that curved surface or arc was continued for a full 360, the radius of the circle then established would be 1
inch. The diameter would be 2 inches.