AAR Circular Letter C-8422

October 20, 1995

CIRCULAR LETTER

(c-8422)

Subject:   Implementation of Modification of Section H II, Rule 3, Inner Ring Placement

TO MEMBERS AND PRIVATE CAR OWNERS

File Number: TWBL – 24.2

In Circular Letters c-8389, dated August 10, 1995 and c-8400, dated August 31, 1995, comments were solicited concerning a proposed modification of Section H II, Rule 3, Inner Ring Placement and Rule 6.10, Selection Criteria. Comments received were positive and the following modifications were approved. The effective date is January 1, 1996 to allow shops time to modify their procedures to implement the modifications.

Modify Rule 3.21 Inner Ring as follows:

Inner rings must be inspected for bearing damage per Rule 1.15 and by methods described in Figure 3.7 and 3.8 or by any suitable method that will indicate condition of inner race. The inside diameters must be checked with dial bore gage (Figure 3.6) or other gages that will enable the accurate measurement of cone bore diameter. Cone bore or gaging must be rotated at least 180 degrees to determine maximum and minimum cone bore diameter. Average cone bore diameter for cone assembly must not exceed tolerance listed in Rule 3.30.b. Cone face wear depth shall not exceed limits as established in Figure 3.6.a.

Add Rule 3.30.b as follows:

The average cone bore diameter for cone assemblies applied to the inboard and outboard bearing location must not exceed the tolerances as indicated below.

 

Inner Ring Bore Size Range

Bearing Class Inboard Location Outboard Location

B 4.0000 – 4.0010 4.0000 – 4.0015

C 4.6875 – 4.6885 4.6875 – 4.6890

D 5.1870 – 5.1880 5.1870 – 5.1885

E 5.6870 – 5.6880 5.6870 – 5.6885

F 6.1870 – 6.1880 6.1870 – 6.1185

G 6.9995 – 7.0005 6.9995 – 7.0010

Reletter present paragraphs b, c, d of Rule 3.30 to c, d, e.

A companion modification of Rule 6.10 also needs to be made as follows:

PRESENT

Rule 6.10 Selection Criteria

The selection criteria are as follows:

1. If the bores are in excess of 0.002" beyond the manufacturer’s condemning limit (see manufacturer’s specification), or are 0.003" or more out-of-round, the inner ring must not be selected for remanufacturing.
2. Inner rings that are scored as a result of having turned on the axle journal cannot be remanufactured.
3. Inner rings that have condemnable defects other than oversized bores must not be selected for remanufacturing by stress relief or stress relief plating.

PROPOSED

Rule 6.10 Selection Criteria

The selection criteria are as follows:

1. Inner rings with bores in excess of 0.0025" beyond manufacturer’s condemning limit (see manufacturer’s specification) cannot be remanufactured.
2. Inner rings that are more than 0.003" out-of-round cannot be remanufactured.
3. Inner rings that are scored as a result of having turned on the axle journal cannot be remanufactured.
4. Inner rings that have condemnable defects other than oversized bores must not be selected for remanufacturing by stress relief or stress relief plating.

These modifications are being progressed to permit salvage of those cones that would otherwise be scrapped due to excessive cone bore growth. This is your authority to modify Section H II accordingly.

Sincerely,

Thomas J. Stahura