There is one thing to take into consideration when permanently attatching a K to M42 adaptor on a M42 lens.
The genuine Pentax adaptor when mounted on a K body is slightly recessed. This is good if you want a tight mount when screwing a lens into the adaptor when mounted on the body. The generic adaptors mount flush, but the lens will wobble a little when mounted. If the Pentax adaptor is chosen the adaptor/lens combination may not fulley lock into place. A generic adaptor would probably be better suited. I have tried both as setteled on the generic adaptor. Bob
