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Bauch & Lomb 7×35 Binocular Repair

Click on this image gallery to follow along with the exciting repair saga. I bought these old binoculars for $12 years ago. One of the eyepiece double lenses had become impossible to see through. It was held together with Canada Balsam that had yellowed, and I took it apart by placing it in boiling water for a few minutes then sliding the two pieces apart. I almost gave up and threw the binoculars away, but then on a whim I bought a bottle of Norland optical adhesive #63 from Edmund optics for like $35 to glue the two halves of the lens back together. With that much money invested, I now felt like I HAD to get these things working again. Everything went smoothly, except losing some of the tiny set screws, and forgetting which side of the lenses was front and back (found out yes this does matter). Put it back together and everything looked terrible, very distorted. Switched all the lenses front to back and reassembled and viola! Now the image looked good. Note to future self, keep track of lens orientation and don’t drop the little set screws!

This is what I started with. I wasn’t sure I was going to remember how it went back together.
First step, clean the prisims.
A screwdriver that fit better would have helped. The slot was very narrow, and made of soft brass metal. I broke at least one screw.
Noticed one of the prisims had a chip missing, but the chip was still held in place by the mount.
Decided to try gluing the chip back on with my Norland Optical Adhesive #63 and curing with UV.
Not too bad.
Before cleaning the prisims.
After cleaning.
Now to this lens. I put dry erase marker on the surfaces to check the fit (they only fit one way)
Then I put a big gob of Norland #63 and pressed them together, wiping the excess off.
Apply the UV light to let it cure!
Put the prisims back in (they have little positioning posts that stick down)
Screw the tube in.
Retaining screw goes in first…
Then this focus wheel…
Lastly the moving eyepiece holders.
Eyepiece goes together. Ignore the lens, it is backwards and the other eyepiece lens isn’t shown.
And front lenses.
Doesn’t look too good. Very distorted.
Some random diagram from the internet. Let me try orienting the lenses as it shows. The eyepiece needs to have the more curved faces pointing inward, and the object lens has the more curved face pointing to the target.
Ahh, much better.
Done! I lost two tiny set screws, so I left all them out. Just means eyepieces can come unscrewed.