Re: Jig transit, aligning ways

I have no experience with the jig transit with optical micrometer, but what
we used back when before the laser levels, to level a long distance (40
foot surface plate in five sections) was primitive but very accurate.
We took a length of 3" angle iron long enough to span the length of the
table and welded caps on both ends that acted as feet and made a trough
of the angle iron. We had a "U" shaped fixture with a depth micrometer on
it that had what looked like a plumb-bob tip on it, a cone pointing
down. We filled the trough with a light oil and would wait for about 30
minutes to let it quit sloshing back and forth. We then took the inverted
U micrometer and measured the distance to the surface of the oil. As soon
as the point touched the oil, it would blink up on the cone, and you could
measure to an accuracy of about 0.00025". You took measurements at the
joints, along the length of the plate, and then made your adjustments. Let
the oil settle down again and re-measure. It was about a two day job for a
big plate, especially if there was a lot of shop truck traffic near where
your were working as the vibration would cause the oil to move.

Kind of low tech, but very accurate.

Don