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measuring the thread /spindle bore of a faceplate

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  • measuring the thread /spindle bore of a faceplate

    How does one measure the thread and spindle bore of a faceplate. I have two old faceplates which are very good condition and I can always measure the spindle easily enough as they are external diameters, but have difficulty getting the exact dimensions of the inside measuremant of the threading of the plate. I have taken a reading of the threads sizes which show up on my gauge as 8g1". What is this in tpi? as the little thread measuring gauge does not tell me this, only 8g1" which is definitely correct, but I would like to know how to measure the spindle bore exactly as well thanks in advance Alistair
    Please excuse my typing as I have a form of parkinsons disease

  • #2
    What the gauge is telling you are two parts of information.
    The 8g1" first off tells you that it's 8 Gauge or 8 tpi what the last part tells you is that because you have a set of old pettern thread gauges these are Whitworth gauges and the standard whitworth bolt equal to 8 gauge is 1" diameter.
    Nothing wrong with these gauges just learn to ignore anything but the gauge size and learn to call gauge pitch or TPI.

    Measuring an inside thread from the bore is never easy as it all depends on the crest radii as to what you are measuring. A standard nut measured from the inside will never give the size given in a set of tables.

    Where faceplates are concerned they are usually in increments of 1/8" so measuring from the start of where one thread disappears into the plate and a guesstimated opposite point will usually give you the size at 1", 1 1/8" or 1 1/4" or whatever.

    John S.

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


    • #3
      Many thanks John that was very helpful I am as usual obliged to you regards Alistair
      Please excuse my typing as I have a form of parkinsons disease