Apart from re-doing balsam achromats, this is by far what I spend most of my renovation time with in the summer! 19th Century lenses loose their WHS even more often than their brass flanges. A complete set is very rare.
In general, I am a believer in black card replacements for the needlessly heavy duty brass stops - except for the larger apertures - say, F.4.5 on a F.3 Petzval. The card width is a bit narrow (fragile) in these cases. Of course, blank brass stops do have a sort of "age" - even when then were made yesterday!
Basically, my system is very basic! Keep the brass you are working on as large as possible for as long as possible - to maximise safety control. Cut the sides before doing holes. Form the base curve before holes. Mark with a pencil circle the maximum aperture without stops. Do the usual focal length, known F value, and diameter at maximum aperture measurements. The equation will not go up completely as the real aperture is influenced by the front lens. It is then a simple calculation to work out the necessary hole diameter to achieve, for example F.4.5 etc.
The hole borers I have attempted to use have never been reliable. Poor cutters for brass sheet, perhaps, more likely poor operations from my side! I have reverted to drilling a hole large enough to take the blade of a stick saw and then remove the brass inside the marked circle as close as possible. Final work is with a curved file.
I have never understood why Waterhouse stops traditionally have tabs which stick out of the slot. I have always left quite a section of the stop sticking out which gives plenty of space for lens information. It must also provide a better light seal, especialy when the slot in the barrel is unnecessarily wide as is sometimes the case with early lenses/projection lenses which have been modified for WHS.
I include some examples of this week's effort. Note I have a double stop using the same principle as wheel/rotary stops - not so difficult a geometric calculation, but it saves a bit on brass plate. The observant reader will note that I have given up the system of cutting out a central square out of the bottom of brass stops which fits over focussing track. Cutting this requires precision and I prefer filling up this gap with either electrical tape or black silicon.
Your experiences are also needed.
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