Ulophot
2-Sep-2019, 19:36
As one whose knowledge of practical machining would fit on the point-end of fine needle, I am asking an idle question. What would it take to measure and create a quality custom adapter filter ring in black at around 39mm? Cost and time. Could a qualified home machinist make, say 20 or 50 and offer at a reasonable cost (i.e., modest profit margin on a competitively-priced item)?
My curiosity was recently peaked by acquisition of a limited-production Leitz lens (made for the Leica CL but fitting the M line), the 90mm f/4 Elmar-C. The filter ring was made with an evidently unique, or at least very esoteric, diameter and/or thread-pitch, so that a special adapter is needed, which, for similarly bizarre-seeming reasons, holds unthreaded Series 5.5 filters. (Why not just adapt to hold 39 or 40.5 mm filters?)
After much back and forth over on the RangeFinder Forum and reviewing alternatives for this oddity, I chose to take the path of an experienced user who has used a 39mm filter for years with no ill effects. The filter threads in about a quarter turn, just enough to keep it in place (burden-free) and not push the mismatched threading into trouble. Works for me.
In any case, having read one post by someone years ago who made his own adapter to a common threaded size, I wonder if one (meaning home machininst) buys a length (say, two feet?) of aluminum tubing that's close enough not to require thinning on a lathe, then slices individual rings from, then cuts the internal and external threads, and finishes them, or something like that.
My curiosity was recently peaked by acquisition of a limited-production Leitz lens (made for the Leica CL but fitting the M line), the 90mm f/4 Elmar-C. The filter ring was made with an evidently unique, or at least very esoteric, diameter and/or thread-pitch, so that a special adapter is needed, which, for similarly bizarre-seeming reasons, holds unthreaded Series 5.5 filters. (Why not just adapt to hold 39 or 40.5 mm filters?)
After much back and forth over on the RangeFinder Forum and reviewing alternatives for this oddity, I chose to take the path of an experienced user who has used a 39mm filter for years with no ill effects. The filter threads in about a quarter turn, just enough to keep it in place (burden-free) and not push the mismatched threading into trouble. Works for me.
In any case, having read one post by someone years ago who made his own adapter to a common threaded size, I wonder if one (meaning home machininst) buys a length (say, two feet?) of aluminum tubing that's close enough not to require thinning on a lathe, then slices individual rings from, then cuts the internal and external threads, and finishes them, or something like that.