On 30 Nov 2004 02:25:01 -0500, (DoN. Nichols)
wrote:


Your'e unlikely to find them in an optics book -- but a
well-equipped machine shop is more likely to have one.

Based on that,
I'm wondering whether an old microfilm reading machine I fished out of
a dumpster could be adapted for this purpose. It's housing is made of wood,
the optics are in metal and it is intended for strips of microfilm,
but I did manage to look at some crystals with it.

Those tend to have more magnification, and less depth of field
than an optical comparator for machine shop work. Also, the screen
tends to be a bit awkward to get to to add a transparent sheet to draw
on. The one I have apparently came with optional lenses for 10X, 20X,
and 40X, but I only have the 20X lens.

A proper one has a collimated illuminator, a stage on which the
object under test resides (with X and Y motion to move the viewpoint,
plus Z for the focus. Usually, there is a way to measure the X and Y
motion -- either with big micrometer heads to move the stage, or with
dial indicators to measure the motion.

However, there are minimal ones which are handheld, including a
set of reticles to measure various things including small threads, and
angles, an eyepiece, and a tube to join them. eBay auction #3855942073
has a set of reticles, but not the eyepiece and tube. I'm not sure, but
I think that the price there is a bit high.

Reliable tools has a nice looking one up for auction
#3856418973, but it's heavy (300 pounds), and is certain to go higher,
as there are over four days left.

There is another by Nikon which is still within reason, and it
suggests an alternative name "Profile Projector" for the equipment.
(Auction #3856039570).

I don't see any of the lightweight ones like mine -- it *looks*
heavy, but is mostly blown plastic shell and a wood base. The size is
necessary to get enough optical length for good magnification. Note
that it *will* take up a lot of benchtop space.

Try eBay searches for "optical comparator" (with the quote
marks) and one will show up sooner or later. A reasonable price is
somewhere in the $200-$300 price range. Unfortunately, this type is not
there at the moment. Note that the same comparator shows up in the MSC
catalog and in sales flyers for significantly more -- reasonable for a
business, but not for a hobbyist. The brand on mine is "Micro-Vu", and
the one on the MSC offering is Fowler, IIRC.

I have a spare Micro-Vu that Id let go really cheap. Screen is in
excellent condition, but the light source was removed for some reason.
Power transformer is fine as is the staging. Might be a good place to
put on a nice bright LED light source.
No dial indicators, clamp your own on.

Gunner

"I mean, when's the last time you heard of a college where the Young
Republicans staged a "Sit In" to close down the Humanities building?
On the flip side, how many sit in's were staged to close the ROTC building back in the '60's?
Liberals stage protests, do civil disobedience, etc.
Conservatives talk politely and try to work out a solution to problems
through discourse until they believe that talking won't work... they they go home and open the gun cabinets.
Pray things never get to the point where the conservatives decide that
"civil disobedience" is the next step, because that's a very short route to "voting from the rooftops"
Jeffrey Swartz, Misc.Survivalism