Originally posted by Lowell Goudge Some (many?) M42 thread mount lenses do not make contact with the data pins on the cvamera body causing the focus indication to not function.
This is not the case. The focus indicator in the viewfinder still functions, no matter whether the data pins are shorted.
What needs the data pins to be shorted to work is the "focus trap" feature.
This is how the "focus trap" feature works: with camera body in AF-S mode, you hold down the shutter release and change the focus, either by rotating the focus ring on the lens, or by moving the camera back and forth. When the image is in focus, the shutter will be released. This is very helpful in macro photography.
Some of the M42 lenses touch the contacts on the camera body's lens mount, but the flange of the lens is painted, so the contacts do not short. In this case, you can use a piece of aluminum foil between the lens and the body to short the contacts, or you can scrape off the paint from the lens flange.
I happen to have the K10D with me now, but I don't have an M42 lens here to test. So I "simulated" and verified the above with a piece of Scotch tape covering the contacts on the lens mount.