November 30, 1989

Circular Letter
(c-7440)

Subject: Revised Roller Bearing Cap Screw Specification

TO THE MEMBERS AND PRIVATE CAR OWNERS ROLLER BEARING MANUFACTURERS AND RECONDITIONERS

File: GC-1463
TWBL-23A
(c-7440)

Gentlemen:

Pursuant to continuing efforts to improve the performance of roller bearings and related components, the AAR Wheels, Axles, Bearings and Lubrication Committee approved the following revision to Section H, Specification S-703-71, Note 3. This revision to assure an adequate level of critical clamping force on roller bearing assemblies becomes effective March 1, 1990.

Present

Note 3. Specifications:
Material: Steel per SAE specifications J429, Grade 2. *Cap screws for freight car roller bearing units (marked *) must be cold headed and roll threaded. The cap screw blank before thread rolling must have uniform dia. Thru its entire length tangent to the fillet radius under the head. This dia. Is that size required for proper thread rolling and is approx. Equal to pitch dia. Bolts and screws must be clean and free of loose scale. All hot made bolts and screws must be tumbled, shot blasted, or equivalent to remove loose scale.

Proposed

Note 3. Specifications:
Material: Steel per specifications J429, Grade 2, with manufacturer certified minimum proof load of 45,000 P.S.I. *Cap screws for freight car roller bearing units (marked *) must be cold headed and roll threaded. The cap screw blank before thread rolling must have uniform dia. Thru its entire length tangent to the fillet radius under the head. This dia. Is that size required for proper thread rolling and is approx. Equal to pitch dia. Bolts and screws must be clean and free of loose scale. All hot made bolts and screws must be tumbled, shot blasted, or equivalent to remove loose scale.

Sincerely,

Leavitt A. Peterson