Originally posted by panoguy If you're thinking of making your own mount, you must be handy...
So why not just hack off the FD mount behind the aperture ring and screw a K-mount flanged adapter onto it.
It's been done before! You'd need to use a spring to hold the aperture-lock levers so it would actually stop-down to the desired aperture when you turn the ring, and then your only worry would be
adding enough distance to get back to the Pentax registry distance.
I was thinking more along the lines of mating two adapters together with perhaps a very thin flange in the middle, or even something like flatting the back of some sort or fd adapter and then braze or solder an infinity focusing m42-pk adapter to the back. Tearing the mount off an fd mount camera for parts also crossed my mind but it seems they are less common (cheap anyway).
I have already converted canon, minolta, olympus and nikon mount lenses with infinity focus but I prefer to remove the mount entirely, screwing on a new mount (off a donor lens or a pk-macro adapter). The thing is, this lens could be worth couple of hundred dollars as is so I'm a lot more reluctant to go hacking it. The cheapest I have seen one go for searching was 140$ on ebay for fd mount like mine without the adapter, from a seller that claimed to know nothing about cameras and didn't know if it worked. The cheapest completed listing right now is170$ with the macro adapter but the lens has haze and scratches and the macro adapter had fungus. The next cheapest was 230$ for m42 mount with the macro adapter (defanatly worth more than mine) so its value falls somewhere in the middle I would think. Mine is in very nice condition.