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SMC Pentax M 50mm lens fix (page 3)


11 Now the time consuming part. You have to install the focus ring and adjust correct focus at infinity. If at step 3 you have figured a way to mark this position before removing the focus ring, reinstall using that mark. I didn't so had to do the following.
Infinity is with the lens element unit adjusted nearly all the way back, when it is so placed install the focus ring, hold it in place and turn it to the 2 extremes. It should hit the stops so that it can't go beyond infinity or the minimum focus distance. If it doesn't stop the silver ring is too far forward (see my comments in step 7). In this case, disassemble it all and make the necessary adjustment. If the stops work ok, replace the 3 screws to hold the focus ring in place, mount the lens on a camera, adjust to infinity and see if far away is in focus. If not you have to loosen or remove the 3 screws and move the focus ring relative to the silver ring until focus at infinity coincides with the focus ring being up against the infinity stop. Good luck! I spent 2 hours on this and am not yet sure if it is right.

12 Finish up by replacing the filter ring with its 3 screws and the front ring. On mine the focus ring and filter ring are so out of round that they bind, so until I can fix that I will be using it without the filter ring (like in the picture beside step 1), should work...
(update: after squeezing the filter ring in the vise I was able to reinstall it and the decorative ring, there is a bit of friction while focusing, but it is usable)

13 Go take some pictures.