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  • bench centres

    what are bench centres used for?Alistair


    http://www.mitutoyo.co.uk/MitProd/mt...3?Opendocument
    Please excuse my typing as I have a form of parkinsons disease

  • #2
    "Used for fast and precise checks of runout on cylindrical/tapered parts"
    That's what it says in the ad....they could be wrong though

    ------------------
    Hoffman in Warner Robins Ga
    Techno-Anarchist

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    • #3
      Allister, We use them for checking runout and truing motorcycle crankshafts. Off course you remove the crank before smacking it with a big hammer(softface).really, thats the recommended method.Doug.

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      • #4
        It is used in quality control dept to check runout

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        • #5
          could it be adapted to true up sharpening wheels? from a bench grinder I saw a device for truing the wheels which looked similar .Alistair
          Please excuse my typing as I have a form of parkinsons disease

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          • #6
            Alistair, I'm sure one could be adapted for truing sharpening wheels. But grinding wheels/sharpening wheels are best trued while they are on the machine which spins them.

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            • #7
              Doug931 I have a polaris 500 crank I want to rebuild. What method works the best when pressing the fly weights back together?
              I have pressed a few apart but haven't tried to press back together. Do you just eye ball them or is there a special jig to hold them true while pressing together, or do you just press a little true a little.
              Thanks for any info. Stephen

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              • #8
                Stephen

                I dont know what a polaris 500 is but assuming it is a single cylinder pressed assembly crankshaft.
                Press the crankpin into the flywheel web with the shortest shaft first, then fit the rod/bearing/washers which you can either hold in place with your fingers or wrap an elastic band around the pin to stop them sliding off in the next operation, set the other flywheel onto your press bars beneath the ram & position the other assembly roughly by eye, using an old crankpin or piece of suitable steel bar of slightly smaller diameter than the new crankpin place this on top of the new crankpin & slowly fetch the press ram down until it just holds the assembly in place, if the flywheels are machined square you can use a 6" rule to check alignment & adjust by gentle taps with a small copper mallet until everything is square both verticaly & horizontaly, carefully press the pin into the flywheel just enough to hold the assembly together (one millimeter or so) then you can remove the assembly to check that they are square & aligned, if not you can correct with copper mallet, then back under the press & being very carefull to watch for tipping press the assembly up to the correct dimension. Truing up should not take too much effort if you took care to align everything as described.

                I would add that the most common cockup is caused by trying to press the pin into the flywheel when it is not parallel to the bore, this will broach material from the pin bore & render the flywheel useless.

                regards

                Brian

                [This message has been edited by pistonskirt (edited 11-28-2004).]

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                • #9
                  Thanks pistonskirt. Forgot to mention it is a 2 cyl 2 stroke in a snowmobile. Your procedure makes sense.
                  Stephen

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