Lens not being 'upright' on the camera


The inner ring of our M42 adapters do rotate as to allow the lenses from various manufacturers (not all of them 'stop' at the same point) to sit 'upright' when mounted on the adapter, the ring is normally clamped down using 3 set screws around the outer ring (3 tiny holes, see attached image).

 

Over time these set screws work their way loose during numerous lenses being mounted and unmounted, they just need to be tightened back up every so often. If you know your lenses always stop at the same 'upright' point, you can use a thread locking fluid on the set screws to help prevent them from getting loose in the future.