Note. Brake discs do not require regrinding as part of normal brake maintenance. Do not regrind brake discs to eliminate the following defects:
- Extraneous noise in the brake mechanisms.
- Uneven and/or increased brake pad wear.
- Superficial or cosmetic corrosion/rust on the working surfaces of the brake disc.
- The wear of the brake disc is greater than the allowable value.
Before regrinding a brake disc, you must first check its thickness to make sure that it is not less than the allowable value. The brake disc is subject to regrinding if its thickness is greater than the maximum allowable and the following conditions occur:
- Increased corrosion/rust and/or pitting.
- Cracks and/or hot spots.
- Iridescent spots from overheating.
- Uneven wear of the brake disc surface.
In addition, regrinding of the brake disc is allowed as part of the process of correcting the axial runout of the brake disc that exceeds the maximum allowable value.
Each time the brake disc is removed from the wheel hub flange, remove rust or foreign matter from the contact surfaces of the disc and flange using cleaning kit CH 42450. Failure to do so may cause increased brake disc runout and brake pulsation.
1. Carefully remove rust from the contact surfaces of the wheel hub and brake disc.
2. Check the contact surfaces of the wheel hub flange and the brake disc to ensure that there are no foreign particles or contaminants.
3. Install the brake disc on the lathe according to the machine manufacturer's instructions, making sure all attachments and adapters are free of debris.
4. Verify that all torsion dampers are in place.
5. With the machine turned on, slowly move the cutting tool until it contacts the working surface of the brake disc.
6. Follow the trace left by the cutting tool. If the track overlaps by at least three-quarters of the circumference of the brake disc, then the disc is installed correctly.
7. If the mark left by the cutting tool overlaps less than three-quarters, reinstall the brake disc in the machine.
8. Following the machine manufacturer's instructions, regrind the brake disc.
9. If, after processing the disc, its thickness is less than the maximum allowable, the brake disc must be replaced with a new one. The thickness of the brake disc must be checked after each boring pass.
10. After regrinding the brake disc, perform the following procedure to obtain the desired non-directional finish:
- Observe the processing speed recommended by the machine manufacturer.
- Use moderate pressure when carrying out final grinding: if the lathe is equipped with a final grinding function, use aluminum oxide sandpaper No. 120; if the lathe is not equipped with a finish grinding function, use #150 aluminum oxide sandpaper.
- After final sanding, clean the working surface of the brake disc with denatured alcohol or an equivalent cleaner.
11. Remove the brake disc from the machine.
12. Measure the amount of axial runout of the installed brake disc. If the value obtained exceeds the specification, regrind or replace the brake disc.
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