Quote Originally Posted by rendoman View Post
At first sight it seems a piston that acts like an hammer. Looking the spring I would think that it works in depression. I remember this tool has a power unit with air flow control. It would be nice to try one!
I think your appraisal is correct. A miniaturized pneumatic hammer. I think a piston could be induced to reciprocate like a two cycle engine - where one port is covered alternately. Light spring operated poppets might work too, opened by piston impact, returning to a starting position triggering that poppet.