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Has Facing a Brake Rotor Been Discussed?

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  • #46
    Originally posted by RichR View Post
    I think it may also discourage the disk from ringing because it's pinched between the 2 cutters.
    Sometimes you need to cut one side at a time on the brake lathe to keep it quiet. Other times I've stacked a heavy weight on the tool holder to tame a chatter. I addition to all sorts of weighted and unweighted bands you can wrap around the rotor. Some rotors will sing like crazy no matter what you do, for those ones I've been known to babysit the machine while holding a wooden dowel against the face of the rotor to kill the vibration. A fresh insert also helps a lot. Sometimes I'll take a roughing pass with a beat insert just to scrape the garbage off the surface and then a finish pass with a brand new insert.

    We've had an Accuturn brake lathe at the shop for the past 26 years, it only has one feed rate so you have to make due. We don't turn many rotors anymore though, with the price of the more common newer rotors you're ahead of the game to just throw new ones on and out the door, and on to the next job.

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    • #47
      Put a rubber band around the perimeter for chatter control

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      • #48
        Contrary to popular belief. it is not necessary to machine both sides of a rotor at the same time. As mentioned in this thread, it is done to provide faster cycle times. Doing both sides at once does not actually guarantee minimum runout or DTV ( disc thickness variation) due to internal stresses being released and some brake lathe manufacturers recommend taking another very light cut after cleaning up all the wear but this increases the time spent per rotor and most operators don't do it.

        This is the procedure that I use on a standard lathe. using a special toolholder that I made, to allow machining both sides (individually) and this allows me to produce a rotor with around .0002" DTV and runout less than .002":-

        1. Machine one side just to clean up any wear or scoring.
        2. Machine the other side to clean up using the opposite hand tool, without moving the rotor.
        3. Repeat 1 and 2 taking .001" per side.
        4. Measure DTV - should be minimal.

        A couple of short videos to show the process.

        https://youtu.be/riDgelmyGTY

        https://youtu.be/YNuiLIxxdXw

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        • #49
          I have cut many a rotor on my lathe with completely acceptable results. Careful attention to set up and dialed in properly and I have/had no issues whatsoever.

          Just $.02
          Last edited by jbacc; 07-02-2018, 10:20 PM.

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          • #50
            One way other than vacuum dust removal is to position a strong magnet or two as close as possible to the cutting tool, removing the build up after every pass. It helped when I have turned chuck backing plates, I have only ever skimmed a small motorcycle brake drum, never a disc.

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