On Tue, 05 Feb 2013 15:20:56 -0800, Searcher7 wrote:
I haven't gotten all of the particulars worked out yet, but I am
working on designing a camera stand and trying to decide on the best
material to make most of it out of.

I'm not trying to reinvent the wheel, but a special project makes it
necessary to be able to take a series of as many as 180 equally spaced
photos across a 45° swing and be be able to do the same again without
any perceptable deviation.

In other words if I take a picture at 12-1/4° and then continue turning
the camera all the way to the end, when I return the camera to the same
spot I took the photo I will need to be able to stop and lock the camera
so that the photo next photo I take there is *exactly the same as the
previous one I took.

This is not plausible with conventional camera stands. So I'm trying to
decide on the best metal to make the moving parts out of. A metal that
will best retain it's dimensions under changing temperature conditions.

To start. Would cast Iron be a plausible candidate?

You probably *are* trying to reinvent the wheel. A rotary table or
an index set probably would work with little modification or
adaptation needed. See for example items in ebay Rotary Tables --
http://www.ebay.com/sch/Rotary-Tables-/41943/i.html -- in
particular,
http://www.ebay.com/itm/Shop-Fox-M10...-with-Divider-
Plates-New-in-Box-/150985935956?
pt=BI_Tool_Work_Holding&hash=item2327768c54,
http://www.ebay.com/itm/Dividing-pla...and-12-rotary-
tables-/180856888044?pt=BI_Tool_Work_Holding&hash=item2a1b e91aec,
http://www.ebay.com/itm/NEW-PRECISIO...-TABLE-3-75MM-
HORIZONTAL-VERTICAL-/170983650642?
pt=BI_Tool_Work_Holding&hash=item27cf6b7552.

The first of those is most likely to work conveniently and
reliably as-is, but costs $259.00 shipped. The table itself has
a 1:72 ratio, and the indexing plates appear to have 18 different
counts, which should cover all but about a dozen of the counts-per-
rotation up to several hundred CPR. The second item, at $80.90
shipped, is just two index plates, with 22 different counts (5
and 6 tracks on top and bottom of each of two plates) and to use
the plates you would need to make a chuck (ie a camera carrier),
an index pin, and a sector arm. The third item, at $60.00 shipped,
is just a small cheap rotary table with a 1:36 drive ratio and 15'
(1/4 degree) graduations on the hand wheel. It would be accurate
enough to repeat well (as long as you approach each position from
the same direction, ie if you compensate for backlash) but much
more tedious to use than an index set. Also see wikipedia's
Indexing Head article: http://en.wikipedia.org/wiki/Indexing_head
--
jiw