American Optical Stereo Zoom; Accessory Thread
Close
Login to Your Account
Results 1 to 17 of 17
  1. #1
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default American Optical Stereo Zoom; Accessory Thread

    I recently purchased a well used Model 570 StereoStar Zoom. As it turned out, this unit had been dropped, cracking the housings containing the erecting mirror boxes (one per eye). I purchased on eBay a for-parts-only model 570 body to get those housings, and was able to assemble a perfectly good model 570, plus a spare set of optical components. Missing are some knobs and screws.

    By the way, one cleans the optics with 91% Isopropyl Alcohol from the drugstore, using cotton balls and/or Q-tips. Do not use any kind of paper, or anything sold for eyeglass lenses. Old 100% cotton tee-shirts, washed and dried (use no antistatic stuff), are also used. And note that the mirrors are coated with pure aluminum on the front surface - very easily scratched. Remove fog, but particles here and there are harmless.

    It is very useful to be able to attach things to the Accessory Port (the ~ 1-7/8" diameter threaded port in the nose of the body), but plain adapters (no lens) et al never come up, so I decided to make one. It´s just a thread, and with the right kind of lathe, one can make any thread, standard or not.

    Now, I never found any details on this thread - AO Proprietary, and they´re not talking, or still exist.

    So, time to measure. Long story, but it turns out to be a mashup of then-standard American threads. (Metric - what´s that?) The purpose of this posting is to publish the details of this thread, so others can also make or have made screw-in accessories.

    The thread form is a standard American Unified 60-degree V shape. It is _not_ 55-degree Whitworth (widely used for microscope objectives.)

    There are 36 threads per inch (tpi), regardless of diameter. It is _not_ the Metric 0.75mm pitch used for optical filters et al; this is equivalent to 33.87 tpi threads, and so closely resembles 36 tpi threads, but they will not mate. Nor can one tell them apart by eyeball, unless one has a thread gage.

    The nominal diameter (max diameter, not pitch diameter) is 1.875" (47.625 mm), not 48 millimeters.

    The above emphasis on the non-metric thread details is because the modern stereo microscope accessory thread is M48x0.75. This is often wrongly called "two inch", which is close (to this and a few other kinds), but a M48x0.75 external thread will not screw into an AO Stereo Microscope accessory port.

    The thread length is 0.125" and there must be a shoulder (where the diameter increases abruptly from 1.875 to 2" in diameter) against which the adapter will bottom, to prevent screwing the adapter in too far and damaging or interfering with the optics within.

    I have machined such an adapter from 6061 tube, and the threads mate perfectly. In the newer, cleaner body, the adapter turns freely but is a snug fit. On the older body, the fit is slightly loose, but is still secure.

    For the record, I measured the Pitch Diameter (PD) of the newly machined adapter thread using the three-wire method. The computed PD is 1.845".

    This adapter is now used to mount a 56-LED ring light, which works better than the original oblique illuminator: AmScope WR63HWR on Amazon, $26 or so. Don´t buy the 144-LED unit - there is a negative review that tells
    why.

    Joe Gwinn

  2. #2
    Join Date
    May 2010
    Country
    DENMARK
    Posts
    3,279
    Post Thanks / Like
    Likes (Given)
    4017
    Likes (Received)
    12716

    Default

    Something seems wrong.

    If the thread is 1.875-36 UNS 2A (1 7/8") then the pitch diameter should be between 1.8558 and 1.8518. Your 1.845 is below minimum. It will of course "fit" but too loose to be correct.

    The external (major) diameter (nominal 1.875) should be between 1.8738 and 1.8683.


    uns.36.jpg
    Attached Thumbnails Attached Thumbnails 001.jpg  

  3. #3
    Join Date
    Jun 2012
    Location
    Tennessee USA
    Posts
    688
    Post Thanks / Like
    Likes (Given)
    333
    Likes (Received)
    403

    Default

    Can't help with the thread form/pitch but a lifetime ago I worked for American Optical as a field/bench tech. Cotton balls and Sparkle glass cleaner was what we used, wouldn't risk using an old t-shirt or anything else but new cotton balls. Light physical pressure should be used when cleaning, especially if there's a coating, reticle, or scale on the lens surface. The mirror surfaces were considered fragile and could be washed but age of the unit made one reluctant to even use a cotton ball on it unless it really required it. That was the advice from the well seasoned tech I learned from and found out the hard way that he was right while calibrating at the crime labs for the state (uh-oh). Not knowing your unit due to advancing CRS my experience from 1979 may not apply but thought I'd pass this along. Hope you get the unit sorted out.

  4. Likes Screwmachine, Colt45 liked this post
  5. #4
    Join Date
    Mar 2001
    Location
    Switzerland
    Posts
    2,527
    Post Thanks / Like
    Likes (Given)
    2272
    Likes (Received)
    1087

    Default

    Quote Originally Posted by AD Design View Post
    The mirror surfaces were considered fragile and could be washed but age of the unit made one reluctant to even use a cotton ball on it unless it really required it. That was the advice from the well seasoned tech I learned from and found out the hard way that he was right while calibrating at the crime labs for the state (uh-oh). Not knowing your unit due to advancing CRS my experience from 1979 may not apply but thought I'd pass this along. Hope you get the unit sorted out.
    I made the mistake of cleaning the mirror in a little Hauser bench top profile projector, I knew they were fragile, just laid cotton balls on wet and picked them off and there went the silvering. Ugh.

  6. #5
    Join Date
    Jun 2012
    Location
    Tennessee USA
    Posts
    688
    Post Thanks / Like
    Likes (Given)
    333
    Likes (Received)
    403

    Default

    Quote Originally Posted by Screwmachine View Post
    I made the mistake of cleaning the mirror in a little Hauser bench top profile projector, I knew they were fragile, just laid cotton balls on wet and picked them off and there went the silvering. Ugh.
    -The seasoned tech that was breaking me in told me what might happen beforehand but said "You need to find out for yourself" and we had a replacement mirror. It amazed me how little it took to ruin the mirror, even a successful cleaning would leave a slight degrading of the surface. Sometimes the surface remains intact and sometimes it doesn't. Sorry to hear we have shared the same lesson. My apologies to the OP for the OT thread hijack.

  7. #6
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default

    Quote Originally Posted by Gordon B. Clarke View Post
    Something seems wrong.

    If the thread is 1.875-36 UNS 2A (1 7/8") then the pitch diameter should be between 1.8558 and 1.8518. Your 1.845 is below minimum. It will of course "fit" but too loose to be correct.

    The external (major) diameter (nominal 1.875) should be between 1.8738 and 1.8683.


    uns.36.jpg
    Thanks for the information. I don't know that AO was using this exact thread, but it's my guess based on measuring two examples. I do know that if the PD was 1.8558", the test piece would not screw into one of the housings.

    I'll try to fit my data to the constraints given in the 1.875-36 UNS 2A specification you provided. And verify the measurements.

    I've been using Machinery's Handbook, 27th edition, as my reference book.

  8. #7
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default

    Quote Originally Posted by AD Design View Post
    Can't help with the thread form/pitch but a lifetime ago I worked for American Optical as a field/bench tech. Cotton balls and Sparkle glass cleaner was what we used, wouldn't risk using an old t-shirt or anything else but new cotton balls. Light physical pressure should be used when cleaning, especially if there's a coating, reticle, or scale on the lens surface. The mirror surfaces were considered fragile and could be washed but age of the unit made one reluctant to even use a cotton ball on it unless it really required it. That was the advice from the well seasoned tech I learned from and found out the hard way that he was right while calibrating at the crime labs for the state (uh-oh). Not knowing your unit due to advancing CRS my experience from 1979 may not apply but thought I'd pass this along. Hope you get the unit sorted out.
    I did manage to clean the optical systems without damaging anything. It's very useful to know that Sparkle glass cleaner works.

    My first approach to the mirror box was with Q-tips dipped in alcohol. This worked, but was awkward and I was worried that I'd damage the mirror surface because I was coming in from the side. I bet that AO had coated the aluminum surface with Aluminum Oxide or the like, because pure aluminum would not have survived.

    Later, as I thought about it, I realized that AO cannot have been doing it this way, and the mirror assembly is held in place with three machine screws. I bet they just wash the mirror box assembly in alcohol and shake it dry. This worked very well, but shaking didn't remove all the fluid. But gentle application of compressed air did. So the recipe became: Remove mirror box from unit. Put box assembly in a small plastic bag. Pour a few ounces of alcohol into the bag with the assembly. Pinch bag closed and shake vigorously. Pour first alcohol bath out and pour new alcohol into bag. Shake again. Remove mirror box assembly from bag and blow the assembly dry. Re-install the assembly into the microscope.

    The various glass lenses were accessible to Q-tips, and a cotton ball held by a hemostat clamp would work.

  9. Likes AD Design liked this post
  10. #8
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default

    Quote Originally Posted by AD Design View Post
    Can't help with the thread form/pitch but a lifetime ago I worked for American Optical as a field/bench tech. Cotton balls and Sparkle glass cleaner was what we used, wouldn't risk using an old t-shirt or anything else but new cotton balls. Light physical pressure should be used when cleaning, especially if there's a coating, reticle, or scale on the lens surface.
    Old T-shirt material does work, but it must be both old (new has too much junk and lint), and *clean*, having just been laundered and dried.

  11. #9
    Join Date
    May 2009
    Location
    Canandaigua, NY, USA
    Posts
    2,851
    Post Thanks / Like
    Likes (Given)
    138
    Likes (Received)
    1257

    Default

    I used to clean very soft scientific coatings on interferometers and the first rule was not to clean unless absolutely positively necessary. We used a technique called drag wiping. This only works on flats. We bought 8x10 (or 8.5x11?) soft lens tissue by the ream, like the stuff Kodak used to sell. You'd tear off a strip a bit wider than the optic to be cleaned and maybe 4" long and lay it on the surface. With an eye dropper you'd drop about 2-3 drops of solvent on the center of the optic, floating the tissue just a bit. Then you'd slowly pull the tissue parallel to the surface. If the amount of solvent was right, it would evaporate on the trailing edge of the tissue, leaving the optic perfectly clean. If the optic was wet behind the tissue it meant too much solvent. Solvent was usually acetone, methanol, toluol or others, depending on the coating and what had worked in the past. Anything water based would have wrecked most of them completely. These were thousand dollar coatings on five thousand dollar pairs of flats with a combined flatness of lambda/200.

    edit- I remember we avoided alcohol because it could leave damaging water droplets.
    Last edited by Conrad Hoffman; 08-20-2019 at 01:42 PM.

  12. #10
    Join Date
    Feb 2004
    Location
    peekskill, NY
    Posts
    24,325
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    4456

    Default

    Standard cleaning solvent for optics was 100 percent methanol, bottled *in*glass* only. Any solvents packaged in polymer
    containers would pick up monomer from the container which would contaminate the optics. +1 on the drag with kodak
    lens tissue. This is an art in itself as conrad mentioned.

    Another handy trick when rebuilding microscopes is the optics lube tends to dry out and chunk up a bit. Clean the
    mechanisms well and relubricate with Krytox pump oil, the kind used for oxygen service. Extremely low vapor pressure.
    Just a tiny bit on the end of a toothpick.

  13. #11
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default

    Quote Originally Posted by jim rozen View Post
    Standard cleaning solvent for optics was 100 percent methanol, bottled *in*glass* only. Any solvents packaged in polymer containers would pick up monomer from the container which would contaminate the optics. +1 on the drag with kodak lens tissue. This is an art in itself as Conrad mentioned.
    Why methanol, versus ethanol or isopropyl alcohol?

    The 91% isopropyl alcohol I used came in a polyethylene bottle (that I had had for at least ten years), but did not leave a film that I could see.

    The bottled-in-glass part would also slow the absorption of water from the air. Avoiding water droplets left after the alcohol evaporates is why I prefer to use compressed air to blow the mirrors dry.

    Another handy trick when rebuilding microscopes is the optics lube tends to dry out and chunk up a bit. Clean the mechanisms well and relubricate with Krytox pump oil, the kind used for oxygen service. Extremely low vapor pressure. Just a tiny bit on the end of a toothpick.
    The grease on the optical zoom assembly cams is light amber in color, very stiff, and not at all dirty or degraded. The cams are aluminum, with steel pins sliding in the milled cam tracks. Nor is there any sign of oil creepage. I wonder what the grease is, but am not tempted to replace it.

    I was looking at Krytox damping grease for optical systems, and Krytox pump oil makes sense for the threads. And helicoid threads in focusing mechanisms.

    The fog on the optical surfaces seems to have come from the various lubricants. There is no trace of films from tobacco smoke or rosin fumes from soldering.


  14. #12
    Join Date
    May 2009
    Location
    Canandaigua, NY, USA
    Posts
    2,851
    Post Thanks / Like
    Likes (Given)
    138
    Likes (Received)
    1257

    Default

    I believe methanol is the best alcohol for removing fingerprints. IMO, alcohol in general isn't very good for oils and greases. One of the more annoying things I clean is the gunky film that comes from plastic boxes, like the ones filter typically get stored in.

  15. #13
    Join Date
    Feb 2004
    Location
    peekskill, NY
    Posts
    24,325
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    4456

    Default

    The story from the optics gurus I worked with was that the process used to distill methanol gave the purest solvent.

  16. #14
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default

    Quote Originally Posted by jim rozen View Post
    The story from the optics gurus I worked with was that the process used to distill methanol gave the purest solvent.
    That sounds plausible. What year was this? Hmm. What grade of methanol was used? That could be the key.

  17. #15
    Join Date
    May 2005
    Location
    AZ
    Posts
    2,332
    Post Thanks / Like
    Likes (Given)
    213
    Likes (Received)
    789

    Default

    I have always used HPLC grade methanol as first choice for cleaning optics in my professional settings. Similar purity acetone is handy as well. For casual work at home, 91% IPA can be made to work with some patience. The biggest problem with any of these solvents is indeed the presence of water, absorbed as humidity from the the air, after opening the containers and dispensing on multiple occasions. Even in Arizona, the land of 7% relative humidity, it's a problem over time for larger containers.

  18. #16
    Join Date
    Feb 2004
    Location
    peekskill, NY
    Posts
    24,325
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    4456

    Default

    Quote Originally Posted by Joe Gwinn View Post
    That sounds plausible. What year was this? Hmm. What grade of methanol was used? That could be the key.
    Oh, long ago. Probably 30 years ago I worked cryogenics in an optics lab. I suspect it was standard reagent grade menthanol, but I do
    recall it had to be bottled in glass.

  19. #17
    Join Date
    Nov 2009
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    310
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    97

    Default Follow-up Report

    I made a prototype adapter to allow one to mount a LED Ringlight to the AO Microscope. While a bit crude, it works perfectly well. A few notes:

    The female thread in the microscope body appears to have been cut with a worn tap - the thread is tapered a bit, a few thousandths in 0.125". Both microscope bodies are like this, but one is cut slightly deeper than the other.

    The recipe for machining the male thread is to turn the outer cylinder to 1.874", and then cut the threads about 0.043" deep into that cylinder. Have not yet measured the achieved pitch diameter.

    The hard part is cutting the thread close enough to the shoulder because a groove is needed. It's far too hard to thread with carriage moving towards the headstock, especially because a high cutting speed is required to cut clean smooth threads. So, I'm using a small HSS cutter with about 13 degrees of back-rake held upside down, and the spindle turning in reverse. (Spindle will not unscrew - L00.) One locates the V tip in the groove, turns the lathe on and adjust to about 900 rpm, and engages the half-nut. It cuts the thread fast and clean. Lubricated with brushed MobilMet.

    It's necessary to verify that the lathe is set correctly by means of a trial run cutting air. I forgot to reverse the leadscrew once, and the lathe carriage took off in the wrong direction when the half-nut was engaged. Nothing broke, saved because the upward force from trying to cut a very deep thread into the shoulder forcibly unseated the Aloris BXA holder. If I had been running forward, something would have broken (unless the mechanical fuse driving the leadscrew sheared in time).

  20. Likes sfriedberg liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •