From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


I applaud your efforts to make the tester "more accurate". 
However, once you attain a smooth motion of the KE, the only other
improvement that can be made is more accurate measurement of the position
of that KE along the axis of the test.
As a result, wood ends up being  a perfectly nice material to use for the
tester.  The screw threads for the rocking motion and the axial motion both
need to be fairly smooth but neither of them has that much of a need to be
precision as the first is just cutting the light level and you will find,
once you start testing, that the table you put the tester on will flex
enough to make changes in the image of the test.  The second motion of the
tester is read by a dial indicator (for the best results) and that isn't
being really controlled all that much by that particular screw, not to
mention that getting to a .002" position is beyond the range of the
persons eyeball in many cases to read the shadows on the mirror and that is
a fair bit of motion compared to how accurate the thread or the dial are.
In other words, you're making your world more complex than it needs to be.
Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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