Looking for info on the L42 L1A1 scope turrets

[Peter Laidler]

Valid point of course re curvature gauge that I mentioned but I was trying to keep it simple.

I would have to admit that the quality of work on some of the L1A1's that I have seen simply beggars belief. Nt so much the optical side but just the assembly afterwards with the over use of silicon sealant that.... anyway. Poor out inspection I say....

Information

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[Warren]

Totally agree on matched lens sets.
Nothing like a 42 or 53 with GOOD matched lenses to replace the lens set in a buggered No.32
When you have the lenses to match up, as happened when the scopes were manufactured it is nice.
The big problem nowadays is finding a decent 42 or 53.
It appears that many ocular lenses and OG lenses in the crop of 32 and 53's out there have had the lenses cleaned with 40 grit sand paper and the crown glass is pooched.
Lenses in a No. 32 are achromatic lenses and consist of two glass lenses glued together by either Canadian balsam or nowadays an epoxy. Not sure when the Brits started to use epoxy.
One lens is crown glass and the other is flint glass. Many couplets are starting to separate or have separated after 70 years and need splitting apart and re-gluing.
I still prefer the balsam glue. Not as easy to use but if you make a mistake you can fix it. Many use the epoxy but if you miss centre they are a bugger to get apart and take another stab at it.
That is why you will see V's cut into the edge of a lens to make sure they to in the correct orientation as well as the lens centre lines up. If you have a focimeter it no problem but few do. I use one on occasion just to check the lenses before gluing them back together.
My old mentor was a advocate for separating lenses in a the frying pan with heat but I still can wait for a few days and use MEK or methylene chloride. I do not have the lenses that were available in the forces.
He was also a master of using spider web for some applications and that is an art within itself.
The glue for spider web was lacquer or ear wax....No ****..ear wax. I wonder what the stock number on that was :-)##
Minor scratches on the crown glass you can polish out with cerium oxide but if you can feel the scratch with a fingernail the lenses are toast.
Glass is not as hard as you would believe and grinding a shirt tail around it to clean the lens is death to it.
I had new glass lenses made and they are no cheap venture. I had them checked out by an optical engineer and the duplication to the original was amazing, plus or minus tolerance. Again: REL and British different.
Most of the time the problems with scratched lenses is the crown glass on the ocular couplet. Trying to match up a set is difficult, but sometimes you get lucky.
There you have a bit of what is involved with the replacement of lenses and when you have a donor scope with good lenses you are in the pink.
Get a bad ocular lens in the donor and the fun begins.
Hope this is of help to some here regarding the replacement of No.32 scope lenses.
You could write volumes on scope repair and the practical end of it . You could fill volumes, but I hope you get the idea.
If you have the basic equipment and some knowledge of optics it is not a bad job.
And, as the manual says: assemble in reverse order....and pray.