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AAR Circular Letter C-7643 |
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AAR Circular Letter C-7643 |
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April 10, 1991
Circular Letter
(c-7643)
Subject: Revisions to Secondhand Axle Journal Diameter Tolerances
TO THE MEMBERS AND PRIVATE CAR OWNERS
GC-WABL
TWBL-23A
(c-7643)
Pursuant to the advent of mandated use of improved measuring devices, the Wheels, Axles, Bearings and Lubrication Committee found that there was a need to make allowances for secondhand roller bearing axles that are now being discovered to be oversized by a very slight amount. Consequently, the Committee advanced revisions to Section G - Part II, Figure 4.10 (copy on reverse side).
After a special study confirmed that the changes proposed are not detrimental, the General Committee adopted the provisions to permit secondhand axle journals to be 0.0005-inch oversize of current specifications -- which heretofore required that secondhand roller bearing axles must have the same journal diameter dimensions as new roller bearing axles.
These revisions are effective immediately and should be inserted in Section G - Part II of the Manual of Standards and Recommended Practices.
Sincerely,
Leavitt A. Peterson
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Bearing Seat Areas Measurement must be taken at three equidistant points around journal at bearing seat locations. The three measurements at each individual bearing seat may be averaged to obtain the average size. Acceptable journals must be within the tolerances in bearing seat areas. There shall be no abrupt changes or steps over the length of the journal, including tapered end. |
| JOURNAL CLASS | MAXIMUM | MINIMUM | A | B | C | D |
| Freight Car Axles | ||||||
| B (4¼ x 8) | 4.0045" | 4.003" | 2-17/32 | 4-31/64 | 4-21/32 | 6-31/32 |
| C (5 x 9) | 4.6920" | 4.6905" | 2-5/8 | 4-57/64 | 5-5/8 | 8-9/32 |
| D (5½ x 10) | 5.1920" | 5.1905" | 2-5/8 | 4-57/64 | 6 | 8-21/32 |
| E (6 x 11) | 5.6920" | 5.6905" | 2-7/8 | 5-13/64 | 6-9/16 | 9-5/16 |
| F (6½ x 12) | 6.1920" | 6.1905" | 2-15/16 | 5-45/64 | 7-1/16 | 10-3/8 |
| G (7 x 12) | 7.0045" | 7.003" | 2-3/8 | 5-15/16 | 6-½ | 9-13/16 |
| Amtrak Axles | ||||||
| D (5½ x 10) | 5.504" | 5.503" | 1-½ | 4-9/16 | 5-1/8 | 8-9/16 |
| E (6 x 11) | 6.004" | 6.003" | 2 | 5-1/16 | 5-5/8 | 9-1/16 |
| F (6½ x 12) | 6.504" | 6.503" | 2-3/8 | 5-5/16 | 6-½ | 9-13/16 |
| Journal Grooving From Inboard Seal Wear Ring | Measuring For Upset Journal Ends |
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| Groove in axle not over .002" deep canbe repaired by polishing with abrasive cloth (80 grit or finer). No abrupt changes or sharp edges are permissible. | Measurement must be taken at three equidistant points around journal, preferably near end of journal. Journal must never exceed 0.003" above maximum diameter in this cross hatched area but may be below the minimum in this area. Upset ends over 0.003" may be corrected per Rule 1A5. |
Figure 4.10
Method of Measuring Roller Bearing Journals
(For Gage, See Figure 5.15)
G-II-40