Fellow member pgk and I thought it a good idea to start a separate thread on mounting flanges, when we got some ideas about this topic on the ‘Filthy Flange - possibilities’ thread. Main reason is that apart from ourselves we guess that a lot of fellow members have a pile of mounting flanges that not fit precisely or don’t fit at all the lenses we have in our collection. Further it seems quite frustrating that in order to acquire a matching lens mount one has to have one made, which is quite costly, or – at least that is what I did several times – buy one flange or a pile on *bay - also quite costly - and many times afterwards discovering that it doesn’t fit.
So why this thread: eventually if there is a need, to be able to have an effective/practical – low cost - exchange of lens mounting flanges between fellow members. To do so we would like to agree on:
a. which measurements and additional info should be provided/needed;
b. how to take precise measurements of the flanges;
c. the thread/form to disclose your pile of spare flanges.
Ad. a. I guess at least the following information should be provided:
1. material (brass, aluminium, alloy);
2. outside diameter;
3. inside diameter;
4. thread (pitch v/s lead and coarse v/s fine) ;
5. number of screwholes;
6. number of visible threads.
I guess it would be too hard in many cases to determine the thread form, depth and angle.
Ad. b. Preferably the outside & inside diameter (and if needed the height) should be measured with calipers. Measurements taken with rulers are less accurate (it would therefore help to judge the measurements if info is provided on how measurements are taken).
Measurement of the thread seems less easy. Screw pitch thread gauges could be of help; there are gauges for Imperial, US and European thread pitches – which could be acquired at low cost. Not sure what the British used before they tried to get to a standard (i.e. I believe Whitworth). The Lens Vademacum has a short section on this topic:
“There are some pointers here:
(a) Old English lenses up to about 1880 came in fairly fine threaded flanges but many were in 1.5 or 2.0in flanges which were roughly standardized between Ross, Wray, Dallmeyer and Taylor, Taylor and Hobson lenses as well as some others. Thus there is a fair prospect of a match here.
(b) After 1880, the English makers tended to use 24TPI threads in a rather wide range of sizes so the problem is limited to finding the correct diameter but the thread is probably standard up to quite large sizes.
(c) Compur and Copal shutters use standard threads and flanges are available from the makers, though care would be needed with older shutters and some old sizes here. Some other lenses have used the same mounting threads but this is not very common.
(d) But there are many exceptions and here a new flange will have to be made with the trouble and expense this involves.
(e) There are a wide range of modern fittings used in miniature cameras, where some are easy to match but others are rapidly dropping into obscurity. The makers name on the lens may suggest the mount, but there are pitfalls as with the Canon lens for the Reflecta which fits no other camera satisfactorily.
It is stressed that the fit should be checked. Dealers can be optimistic as to whether threads match and have a tendency to screw lenses into flanges where the fit is surprisingly poor- half a turn and it jams suggests the wrong pitch rather than the right flange! What is needed is a smooth action and several turns till it screws up tight.”
Further pkg pointed me to the site of skgrimes on how to measure the thread pitch precisely: http://skgrimes.com/library/faq/how-to-measure-threads
Ad. c. Where to present our piles of spare flanges? I guess as long as we do not put up our flanges for sale or explicit exchange – it would be no problem to have them listed in this thread with all their specifications – having the possibility to have a discussion about them (like the many threads on lenses). However, when one wants them for a sale or exchange, the mounting flange should be listed in the correct “For Sale/For Trade” section.
If this provides a lot of info, we might take it further to a database on lenses / lensmount specifications.
More input from fellow members on these topics are welcome
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