In article ,
Cigi wrote:

[ ... ]

Agreed. For comparison use it doesn't matter.
I try to avoid taking readings from the DTI face if at all possible.
Work to zero and take the reading from the height gauge/machine
readout. If you must read from the dial keep the stylus arm as
straight to the indicator body as you can to avoid cosine error.
More angle=more error.

Note that some makers design so the proper reading is given at a
specific angle -- not necessarily 90 or 0 degrees to the work surface.
An angle of 30 degrees will give a 2:1 motion modification -- and will
hold the pivot point clear of the work surface (if you are dealing with
a large radius), so some makers design for it to be correct at such an
angle. All the more reason for you to chase up an old Lufkin catalog
and find out both what length and what angle you need to use.

Or you could set it up on a stable surface, then slide a piece
of shim stock under it to deflect it a known amount. This will show you
how many marks it goes for say 0.001" of pointer motion -- and you can
try different angles to find one which works well. (You could probably
even find a combination of angles and pointer length to give your
readings i Metric units, should you so desire.

Good Luck,
DoN.

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