1.1 This specification covers heat-treated alloy steel axles for mass transit and commuter cars in electric and locomotive hauled railway service.

1.2 This specification is for solid design roller bearing axles with machined bodies.

1.3 Various axle designs are used for this service including motor and non-motor with either inboard or outboard journals.

1.4 Supplementary requirements including those in the general requirements of Specification A 788/A 788M are provided for use when additional testing or inspection is desired. These shall apply only when specified individually by the purchaser in the order.

1.5 Unless the order specifies the applicable "M" specification designation, the axles shall be furnished to the inch-pound units.

1.6 The values stated in either inch-pound or SI (metric) units are to be regarded separately as standard. Within the text and tables, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.