There exists threads on the topic of separating and re-cementing lens elements already. But I've seen references touching of the miking of the original cement job with a micrometer so that the repair job will end up identical. So this leads me to speculate that the thickness glue film itself comes into play. So this leads me to a question which is the point of this post. And my question is: is it really all THAT important? If it is then I believe I have devised a method that ordinary people can do with the use of a drill press. Many ordinary people have at least a tabletop drill press, or access to one. Once a trustworthy person answers my question I am prepared to go into my idea. I can see the point of marking the edge of the lens stack before disassembly to make sure each is turned by the clock for reassembly, but once again my question is, would it not be enough to squish out the excess glue between the fingers and take whatever finished thickness you end up with? Or are these lenses ground and engineered so that the finished thickness be exact? And to what tolerance? Thanks.