Got a Leitz Hektor 120mm f2.5 Projection lens a couple weeks ago, and I have thinking of making a lens out of it. By itself, a project lens has no aperture, no focusing mechanism, and therefore not very useful except on a projector. Since I don't know how to make lens parts, the only way I can make a lens is to use a barrel from an existing lens, and plant the projector lens in. This is easier to do than you think, and it's a lot of fun to do.
Tools: You don't even need a lot of tools. A Dramel with cutter attachment to cut the projection lens to to shorten its length. A file to smooth the cut. Small screw drivers to remove the mount of the lens to take out the lens elements inside, and glue. I used Gorilla Glue, but it has one nasty side effect -- it expands.
The projector lens -- Larger Picture.
The Lens Barrel -- This will be the hardest part. You need to find a lens with a 135mm focal length, and an front opening large enough to accommodate the projection lens. The one I found that fits, is the Enna Munchen 135mm f2.8. Unbelievably, this is one of the worse lenses I have seen, and the only one from West Germany. The outer shell is made of plastic, the front element assembly that holds the glass is made of plastic. Because of this, the thread quickly wore out and the front element assembly could no longer be screwed in tightly. One reason to scrap it. Optically, it's also a dog. In a word, a worthless lens. Anyway, it fits the Hektor 120mm f2.5 lens.
Donor body -- Enna Munchen 135mm f2.8 M42 Mount. Larger Picture.
Happy together before operation -- Larger Picture.