Originally posted by mabelsound The problem isn't the lens coming unscrewed from the adapter--that is generally more than secure enough, as secure as any screwmount lens on a screwmount camera. It's that the adapted lens does not lock in place the way a K-mount lens does--you don't need to press the release button to unmount it. If the focus is stiff, the lens can come loose from the camera while you're shooting. "Threadlock" doesn't address this problem--but as bobpur says, perhaps it's less a problem than I think.
100% Agree!
The thread lock should keep the adapter on the lens w/o modifying lens or adapter but doesn't address the issue of lens/adapter actually locking into place. I use the Original Pentax Brand m42 adapters and never have problems removing from camera body. I've got a couple of heavier m42's and I think w/o the locking mech in place I would accidentally unmount theses lenses while zooming or focusing, and you know might happen next...