To: atm{at}shore.net
From: Andy Saulietis 
Reply-To: Andy Saulietis 


Re,



>If the grooves have to be short, as they might for a telescope cage, then
>you'll need to keep tolerances only reasonably good, say 1/8" on position
>on a 10" diameter scope.
>
>One way to think of it is, mentally drop one ball into a groove (all the
>grooves in this example are oriented radially away from the center).  That
>ball is free to slide in that groove.  Now rotate the part with the balls
>in it so a 2nd ball drops in the groove.  The two balls are still free to
>slide in their grooves, though not independently, by rotating and
>translating the part.  If the grooves are infinitely long, you can always
>move things so the 3rd ball drops into its groove.  Real world grooves
>have finite lengths, so it is possible that one or more of the balls runs
>out of groove before it drops in.  This is where you'll need a little
>ordinary precision.
>
>I use this all the time where I work, and it really does get micron
>repeatability for stiff, clean parts.
>
I agree, if one is willing to give up a predetermined linear position for
the kinematic mount. The cone/groove/flat method also locates the xyz
position to a specified location.

The cone is just a convenience..it can also be replaced by 3 flat surfaces
ideally 90 deg apart (corner of a cube), so the two k-mounts are
kinematically similar.


Andy Saulietis
ISS Enterprises
PO Box 19
Mayhill NM 88339


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