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    Re: first mirror artifical horizon test
    From: Richard M Pisko
    Date: 2011 Mar 27, 22:03 -0700

    On Sun, 27 Mar 2011 18:49:39 -0700, Bill Morris 
    > This is an interesting application of the differential screw principle,
    > sometimes used in machine tools like surface grinders to make fine
    > adjustments. It has also been used in a micrometer head, though not as
    > far as I know as a commercial proposition.
    I'm very glad you understood my description, and I was actually using the
    device as a micrometer head to adjust a front face mirror at the end of
    another piece of lath.  I still have the spread sheet with my readings and
    various distances to about 500 yards.  I called one turn 0.005 inches, and
    had five longitudinal lines drawn on the masking tape.  I could estimate
    to approximately 0.0001 that way.
    > There are "quick and dirty" ways of tightening a nut around a screw. The
    > nut can be split longitudinally and closed up a little in a vice, or it
    > can be split tranversely across the full diameter of the thread while
    > leaving part of the wall intact and closed up a little in a vice.
    That was the effect of the shrinkage of the outer tube on the two ground
    off nuts, an axial compression.  I wish I had thought of that *before* it
    happened, though.
    > A more refined way of closing this latter is to drill and tap for a
    > small diameter screw.
    Ahh . . . .  My skill is not to that level, but I think I may tighten the
    plate-nut by your second method, one or two transverse cuts and judicial
    use of a vise, then lap the threads for a smooth fit.  The project has
    been abandoned, but I may as well make this improvement for use in a third
    Thank you.
    Richard . . .
    Using Opera since the"Dog" died

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