Friday, August 23, 2013


     It showed up ay a popular auction site: a genuine GR calibrated knob:
     In the original box (love those fonts!):
      With an "index:"
     Actually, three of them, and that's the part you never see.  Sure, it's just (just?) a line scribed on a piece of metal, the same nickel-plated brass as the calibrated skirt, but it's mounted on a little leaf spring and shaped to ride right on the edge of the calibrations. It beats the usual crude expedients by a long ways.

     There's one fancier replacement, a vernier scale that allows reading the dial to a tenth of a division.  Either one is a nice thing to have when the urge to build some interesting device happens to strike.


  1. Is this a vernier drive one, or "just" a knob that fits on a shaft?

  2. "Just" a knob -- in size and appearance, it's a near match for the Crowe reduction drive unit I bought at the Indy hamfest. GR made a little pinch-disc edge drive for these knobs, which gave a ~5:1 reduction. (National did the same for the similar-looking type O knob with calibrated skirt. Theirs was the "O dial drive," part number ODD!)

  3. Pretty neat. It looks new.

    I had a few of these and a few verniers from helping to clean out an SK's shack. I didn't have a use for them at the time, so I sold them on eBay.

    Still kicking myself over that.....