Home brew focusing helicoid with 55mm & M42 mount. Click to see larger.
I spent the long weekend last week getting my home brew focusing helicoid to become sort of modular. Currently, it has a 55mm thread made out of a filter (without glass, of course), and I also made an M42 mount. Together with the thinner 17-32mm helicoid that I bought, I can now use most of the odd lenses I have. I am very glad that I have a large collection of step-up/step-down adapter rings that I got from the old Outlet Store. They are now finally being utilized, especially the 55<-->52mm, 52mm <--> 49mm. Perhaps I saw this coming :)
To make the lenses focus to infinity, I simply add/remove filter rings. The advantage of this kind of adapters is that I can bring a few spare filter rings and add them on if I need to do some close up.
Next project is to make a focusing helicoid with aperture control, so that I can use the projection lenses and have control over depth of field.