Repair Of Standard Stick B-Plate Cracks Caterpillar

Repair Of Standard Stick B-Plate Cracks

Usage:

461B (8SG, 8ZK);
426B (5YJ, 6KL);
428B (7EJ);
436B (6MJ,7FL);
438B (3KK) BACKHOE LOADERS

Problem:

The U-shaped plate which forms the stick cylinder boss may crack.

Solution:

If the U-shaped plate which forms the stick cylinder boss is cracked and the crack has grown out into the side-plate(s) of the stick, the cracked stick should be replaced.

If U-shaped plate is cracked, but "HAS NOT" progressed out into the side plate(s) of the stick, repair the stick with the following procedure.

Inspection/Repair Procedure:

NOTE: The following procedure is to be used only if the U-shaped plate is cracked, but "has not" progressed into the side plate(s) of the stick. 1.

1. If the crack is only present in the top binocular plate, the repair can be made on the machine. (Be sure to inspect the underside of this radius area. If cracks exist in the underside, the stick will have to be removed from the machine.)

2. If the stick can be repaired on the machine, skip to step 4.

3. If the stick is "NOT" repairable on the machine (as defined above), follow the procedure defined in the service manual for removing the stick.

4. On previously inspected sticks with cracks, it has been noted that an excessive fit-up gap exists between the top and bottom plates and the U-shaped plate. Use an air carbon arc torch or similiar tool to remove material from the crack in the plate(s) and form a bevel on the plate which can be welded. If the crack extends into the top or bottom plate material away from the weld, repair this area as well. Refer to illustrations 1 and 2.

5. Reweld procedure for the U-plate (see illustration 3): Use Shielded Metal Arc Welding with AWS E7018 or AWS E7028 electrodes for this welding procedure.

First pass (10mm bevel groove weld) needs to be directed into the root of the intersection of the U-plate and top/bottom plate.

Second pass is a V-groove weld directed at the intersection of the first weld and the top/bottom plate to finish filling the groove.

Third pass is an (8mm) fillet between the U-plate and the top/bottom plate.

6. Reweld any grooves (cracks) out into the parent plate. These welds should be filled and ground flush (see illustration 4).

7. Clean up repaired surface and paint. 8.

8. Assemble as per service manual.