I use lenses modified this way on a Canon EOS 5 film SLR, attached in this manner they're fully manual for both aperture and focus as the camera can't talk to them, and it's your own eyes that will be doing the focus confirmation - just as it always used to be.
My camera is perfectly happy with this and will figure out it's own shutter-speed to suit whatever aperture you manually set, or alternatively you can switch to full manual and figure the shutter-speed out for yourself for more control.
The same basic principles will apply to any other type of lens you can get a suitable adapter for, but couldn't normally use on a full-frame camera because of stuff sticking out of the back.
Please be gentle with me - this is my first Indestructable. :-)
Step 1: What you'll need:
A K-mount lens
A tiny cross-head screwdriver
A lens-cap or similar container for the tiny screws
A mouse-mat or similar to stop things sliding around
Some cutters that can cut both metal and hard plastic - I used a pair of pincers
Step 2: Dismantling the lens
Place the lens on the mousemat with the end that normally goes to the camera facing upwards
You'll see a few tiny crosshead screws, remove those and keep them safe - try not to drop them on the floor or you're going to curse trying to find them. Don't ask how I discovered this...
Once the screws are all removed, the plate with the bayonet fitting should be able to lift clear - be careful as some lenses may have spring-loaded parts hiding to poke holes in the eyes of the unwary... mine didn't so all was ok.