Brake rotors that lack a smooth, non-directional finish make more noise and wear out more quickly. The metal finishes that have replaced asbestos linings are noisier, however, and customer complaints about squeaky brakes can be heard at many car repair shops. But unless the final finish is perfectly smooth, brake noise will occur. In fact, any surface irregularities on drum brakes can cause an irritating squealing, humming or slapping sound. Disk brakes make nuisance noises caused by harmonic vibrations, too.Although some automotive suppliers and repair shops use sanding disks, others choose ball-style flexible hones for rotors. These honing tools are recognizable by their abrasive globules, sometimes called “dingle berries”, which are mounted to nylon filaments. Ball-style flex hones have been used to de-burr bored metal, but can also remove tiny metal shards and fragments. These same finishing tools can be used on flywheels to remove cut, folded, and torn metal fragments.
When brake rotors are made, machining introduces slight flaws and resulting noises. By polishing off the slight lead-in groove or score, however, flexible honing can create a super-smooth surface that is also non-directional. The result, as Miller Industrial Products learned, are quieter brakes that last longer.
Based in Jackson, Michigan, Miller Industrial Products makes brake drums for Cadillac stretch limousines. These luxurious passenger cars are equipped with bulletproof glass and doors, as well as a heavy-duty undercarriage with weight axles. The braking system for such stretch limos requires brake drums big enough to fit a truck, but Cadillac customers demand and smooth and silent ride – not slapping sounds.
To eliminate brake noise completely, company president Bill Miller chose ball-style flexible hones and developed a “special process” to machine the brake drums and hone them until they were silent। “And it worked so well,” Miller adds, “that the engineers at Cadillac were amazed.”
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