Originally posted by newarts I recently converted an OM mount lens to a K mount. It was easy.
I removed the OM mount flange & replaced it with an m42->pentax K adapter (
the kind with the flange).
I just drilled holes in the adapter to match the screw locations on the lens. Infinity focus is ok.
I think, that you must missed something in your description, because this way the aperture will be always open. Or you have another design of lens than I have.
Yesterday, i have finally done my conversion of ZUIKO 50mm 1.8 MC AUTO-S. It was my favorite lens from my Olympus age and I've always regretted that I can not use it on my Pentax bodies. But now, I can!
I have done it exactly same way as you. Removed top plate from mount, remove some parts from inside, drill holes in cheapo m42/PK adapter - but here is a catch. I need to secure some levers in positions to retain aperture close. I used black hard paper for it. It retain one lever in position and protect part around back lens part (and reduce reflection).
Now, I've done some testing, and I'm very pleased. This lens beat up DA 50 1.8. And from f5.6 is on par with my DA*50-135 in terms of sharpness (color rendition has better the star lens). And has really nice bokeh.
So, big thanks to all in this thread, because this has led me to using my beloved fifty again