AAR Circular Letter C-8665

November 21, 1996

CIRCULAR LETTER

(c-8665)

Subject:   Implementation of Manual of Standards and Practices, Section H, Part II, Rule 6.25

TO MEMBERS AND PRIVATE CAR OWNERS

File Number: TWBL – 24.2.1

In Circular Letter c-8590, dated July 10, 1996, the AAR published the addition of Rule 6.25 to Manual of Standards and Recommended Practices, Section H, Part II. This rule was further revised by the Wheels, Axles, Bearings, and Lubrication Committee based on comments received when the rule was initially published. The Committee has updated the rule as shown on the reverse of this letter. The changes made are shown in bold on the revision.

This is your authority to update your Specifications accordingly. These changes become effective upon this publication to the railroad industry and will be incorporated in Section H, Part II upon its revision.

Sincerely,

Thomas J. Stahura

Director – Equipment Performance

RULE 6.25 REFINISHING REQUIREMENTS FOR INNER RINGS WITH BACKFACE WEAR

For the purpose of this rule, refinishing includes grinding, machining or other AAR approved methods.

Inner rings with backface wear exceeding AAR limits may be salvaged by refinishing the entire width of the inner ring backface in accordance with the following guidelines:

1. The amount of stock removal to eliminate backface wear will be limited to the existing wear groove depth of 0.0100 inches, whichever is less.
2. An inner ring backface may be ground or machined only one time.
3. After grinding or machining, sufficient original marking must remain to identify the manufacturer and date. The original equipment manufacturer may restore name and date using laser marking, pantograph grinding, dot matrix stamping, or other AAR approved methods. Freehand grinding of manufacturer’s marks is not permitted.
4. Reground or remachined inner ring faces are to be identified with a capital "G", date and shop code.
5. Any "circle R" mark, "circle P" mark, shop marks, and repaired spall marks, as well as any additional pre-existing markings, shall be transferred to the reground inner ring face.
6. The machined surface shall be 125 RMS or less and free from tool marks, chatter waves, grinding scratches, pits, rust, discoloration, or any other visible surface imperfections.
7. All parts must be precleaned per Rule 1.10 before grinding or machining. If cages are left in place, parts must be cleaned per Paragraphs 3.9 and/or 3.10 after machining. If cages are removed, all parts must be inspected per Rule 3.29 before reassembly. All parts must have all matter removed and be thoroughly cleaned prior to reuse and must meet all finish requirements specified in this manual.
8. Sharp edges are not permitted. A radius on the finished surface must be maintained so as not to interfere with the application of the roller bearing.
9. The front and back face of the inner ring must be parallel within .001 inches after refacing.
10. Refinishing inner rings is the responsibility of a bearing manufacturer or a shop certified by the AAR, per Appendix A, Paragraph 6.0.