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  1. #1
    Join Date
    Aug 2010
    Location
    Near Bendigo, Victoria, AUS
    Age
    72
    Posts
    3,102

    Default Measuring microns and their decimal fractions

    Some of you may have read RayG's descriptions of one of his amazing acquisitions - a late 50s to 70s HP Laser Autocollimator and auto compensated interferometer.
    I've now seen it in use in person and had both my cast iron and granite surface plates 're-certified' - well, at least checked for deviation from flat.
    This is an amazing process - not that easy to get your head around and quite time consuming.
    My surface plates appear to both be within about 5 microns per foot. Maybe one day I'll blue and spot them against each other - if I get bored....
    Here are a couple of pictures of some of the set-ups and equipment:
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  2. #2
    Join Date
    Oct 2012
    Location
    Australia
    Posts
    621

    Default

    ""
    Dr. Egon Spengler: There's something very important I forgot to tell you.
    Dr. Peter Venkman: What?
    Dr. Egon Spengler: Don't cross the streams.
    Dr. Peter Venkman: Why?
    Dr. Egon Spengler: It would be bad.
    Dr. Peter Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad"?
    Dr. Egon Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.
    Dr Ray Stantz: Total protonic reversal.
    Dr. Peter Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon.


    ""

  3. #3
    Join Date
    Jun 2008
    Location
    Victoria, Australia
    Age
    74
    Posts
    5,080

    Default

    Hi Joe,

    When I get some time to get the plotter going and figure out how to run the surface plate calibration software, we can have another go at that and try to produce a proper calibration chart.

    Thinking back on what we did, that cast iron plate that Marco ground is probably every bit as good as the granite, especially the center section which is probably better than 2 microns... I wouldn't scrape the cast iron to match the granite, might be the other way around..

    Regards
    Ray

    PS.. Yep don't cross the beams..

  4. #4
    Join Date
    Oct 2012
    Location
    Australia
    Posts
    621

    Default

    The sensitivity really is amazing.

    A while ago I used it to measure the twist in some plane bodies see this thread here. or if you prefer video here

    With the setup pictured I could place a single M4 nut on one end of the bar and read off how much twist that caused in plane body to two signification figures. The other interesting effect that you could actually see happening is what happened during the application of the load and after removal. In the X10 mode (not in video) it would twist quickly after carefully putting the load on and then twist some more over the space of 30 seconds then slow down and settle. When the load was taken off the the body would spring back to 99.9% of original shape and position and then take about a minute to settle back to 99.9999999%.

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