advice for aperture pin problem

[rbelyell]

hello friends

i have been collecting m42 lenses for my sigma sd14 for about 2 months now and i find i have two lenses that have aperture pins sticking out of the mount side that must be depressed in order to stop down the lens. unfortunately they do not depress when connected to my camera adapter. all other lenses work fine except these two. any suggestions?
thanks
tony

[luisalegria]

Sometimes you need an adapter designed to press the aperture pin. Alex (hk300) had some, I don't know if for Sigma.

Alternately, anything is possible, depending on the case. I have modified lenses to permanently depress the pin, or achieve the same effect in the internal mechanism. I have drilled and tapped the lens mounts for plates to hold down the pin, reversed internal springs, removed or disconnected internal springs, added shims internally, etc. Some people have done this sort of thing with glue.

You could also consider modifying your adapter.

[Poolhall]

Basically the easiest and reversible method is to unscrew the end of the lens and put a sleeve over the pin, use either a cutting from q-tip, or some plastic wire insulation, then screw the lens base back on so that the sleeve stops the pin poking through the hole and keeps it depressed. This turns your len into a preset, i.e the pin is permanently pushed in . If you look on the forum the technique is described with pictures somewhere, try under q-tip method or m42 auto or the like edit I think alex did have sigma adapters like that a while ago

[hinnerker]

The simplest way is to unmount the lens and get rid of the pin. Fix the function inside, mostly this is as easy as your creativity.There is no special hint, the lenses are to different in mechanical realisation. Be creativ! And store the pin in a safe place and enyou the lens.

Its reversible and safe

Cheers
Henry

[rbelyell]

i must say the people in this forum are very nice and helpful! thanks to everyone. i overcame my innate fear of mucking things up and unscrewed the lens back and disabled the spring. it works fine now! my first successful lens operation, mother and optics are doing fine! thanks again for your help.
tony