Owen Duffy wrote:


Tom, I don't understand the reference to expensive equipment, the system I
described of placing a short close fitting rod in the first hole and
visually aligning the rod with the drill for each additional hole is very
low cost and adequately accurant.

Owen

Owen

I was refering to another of your posts -

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Wes, I agree, that is entirely practical. As far as bubble technology goes,
senstivity easily exceeds that, IIRC the plate bubble sensitivity on
theodolites is commonly around 20" (seconds) per 2mm run. By reversing such
a bubble and splitting the difference, it should be possible to achieve an
error well under 0.1mm/m slope.

Realistically, most bubbles for engineering workshop use would be more
accurate than the drilling process, so they are a quite adequate means of
registering the work.

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As has been described and documented in the last few months (not here,
but in science journals), emails, and their equivalent, are sometimes
the most misunderstood things in the history of human communication.
The problem is even worse in a newsgroup, because the threads are huge,
and replies sometimes reference posts not in the current sequence, and
people receive items out of time order and often delayed.

tom
K0TAR