Power Feed to Make Threads (English or metric threads) Curiosity

[Christianstark]

“So after all of these years, if I still have that right, a rotation of that wheel by one full turn would have moved the lens in less than 180 microns. At 40 microns per 0.001" that meant that it moved 0.0045" per turn ... which is 222TPI! Maybe my memory of the numbers is off by a factor of 2, but even if so, this is some pretty fined threads in that brass barrel! More a kin to what Bi11 was talking about.”

This was likely accomplished with a differential screw, rather than threading so fine.

 

[B2]

Maybe, It has been a long time ago. However, there was only one shaft (the brass that mounted the lens) and one outside barrel that was fixed to the handle. I could turn it fairly long distances, like a centimeter, and I do not recall any intermediate barrel or nut. I never took it apart as I was afraid I would never get it back together. There was a substantial mount of grease which I assume was to take up the spacing of errors and to make it stiff to turn. A way of mounting one piece relative to the air-bearing so that it would move longitudinally along the center axis. I do not recall. Don't for get that the whole thing had to be hollow to allow the light beam to pass to through the handle, the barrels and finally the lens. The OD of these high power lenses are less than 1cm and you cannot block any of it without giving up some numerical aperture and hence the minimum size spot that can be made. The lens barrel was the original from the microscope objective but had been turned down to just a shell to allow for the threading etc. The OD of the outside barrel was not very large either. But all of this is just a distant memory now. So.... Later I had several other interactions with the Tech. He was really good!