April 20, 1990

Subject: Dial or Digital Snap Gage
To: Members and Private Car Owners

TWBL-12
(c-7478)

Gentlemen:

Recognizing that Circular Number D.V. 2156, dated November 20, 1989 approved the mandatory use of dial or digital snap gages for measuring axle journals, the Wheels, Axles, Bearings and Lubrication Committee determined that the use of these types of gages is permissible immediately and mandatory as of January 1, 1991.

Appropriate revisions to Section G-Part II, Rules 1C4 and 1K4 are enclosed.

Sincerely,

Leavitt A. Peterson

Present

Rule 1C4 Journals must be carefully measured each time a roller bearing is removed to determine whether the journal is within prescribed tolerances. Journal diameter measured in critical areas, as shown in Figure 4.10 and located with roller bearing seat location gage in Figure 5.15, shall not vary more than .001 and there shall be no abrupt changes or steps over the length of the journal. Axle journal, journal fillet and dust guard seat must be cleaned (whenever using abrasive cloth for cleaning, only 80 grit or finer is permissible). Indications of fretting checks on the periphery of the journal fillet, within 3/8 of the dust guard seat, need not be removed as long as the fillet is in compliance with Figure 4.11. Fretting corrosion on journal fillets may be removed with abrasive cloth (80 grit or finer). Fillets with excessive U dimension is not reduced below minimum length and checked with the gage shown in Figure 5.21. Any journal with depressions, surface defects, high spots or upset ends should be carefully refinished so as to remove them from the circumference and length of the journal providing the journal diameter is not reduced below minimum and the surface roughness meets specifications. See Figure 4.10 for repairing grooves caused by inboard seal wear rings.

Proposed

Rule 1C4 Journals must be carefully measured each time a roller bearing is removed to determine whether the journal is within prescribed tolerances. Journal diameter measured in critical areas, as shown in Figure 4.10 and located with roller bearing seat location gage in Figure 5.15, shall not vary more than .001 and there shall be no abrupt changes or steps over the length of the journal. Dial or digital snap gage (with 0.0001 scale) must be used to measure journal diameter and must be calibrated using the master disc (at least Class X tolerance) that is the same temperature as the axle being measured unless appropriate compensation is made for the temperature difference between the master disc and the journal being measured. Axle journal, journal fillet and dust guard seat must be cleaned (whenever using abrasive cloth for cleaning, only 80 grit or finer is permissible). Indications of fretting checks on the periphery of the journal fillet, within 3/8 of the dust guard seat, need not be removed as long as the fillet is in compliance with Figure 4.11. Fretting corrosion on journal fillets may be removed with abrasive cloth (80 grit or finer). Fillets with excessive U dimension is not reduced below minimum length and checked with the gage shown in Figure 5.21. Any journal with depressions, surface defects, high spots or upset ends should be carefully refinished so as to remove them from the circumference and length of the journal providing the journal diameter is not reduced below minimum and the surface roughness meets specifications. See Figure 4.10 for repairing grooves caused by inboard seal wear rings.

Present

Rule 1K4 Axle journal, journal fillet and dust guard seat must be cleaned with a wire brush or other suitable means. Journal diameters on new, secondhand or reclaimed axles must be checked for proper size and journal ends for upset condition (Figure 4.10). Check for proper fillet with fillet gage (Figure 4.11) to insure proper seating of backing ring. Excessive galling or fretting of the fillet will require scrapping or reworking the axle, in accordance with established dimensional allowances. Axle ends must be clean and free of dirt and contaminants.

Proposed

Rule 1K4 Axle journal, journal fillet and dust guard seat must be cleaned with a wire brush or other suitable means. Journal diameters on new, secondhand or reclaimed axles must be checked for proper size and journal ends for upset condition (Figure 4.10). Dial or digital snap gage (with 0.0001 scale) must be used to measure journal diameter and must be calibrated using the master disc (at least Class X tolerance) that is the same temperature as the axle being measured unless appropriate compensation is made for the temperature difference between the master disc and the journal being measured. Check for proper fillet with fillet gage (Figure 4.11) to insure proper seating of backing ring. Excessive galling or fretting of the fillet will require scrapping or reworking the axle, in accordance with established dimensional allowances. Axle ends must be clean and free of dirt and contaminants.