Dugg writes in -One reader of The Automata / Automaton Blog wrote to me with an interesting question. "I'm looking for a simple mechanism to convert rotational motion to reciprocal motion along the SAME axis as the rotation, not perpendicular."
I decided to investigate potential solutions in one of my favorite books on mechanisms, Five Hundred and Seven Mechanical Movements: Embracing All Those Which Are Most Important in Dynamics, Hydraulics, Hydrostatics, Pneumatics, Steam Engines... (Astragal Press, 1995).
Answers and more here. Looks like a great book!
http://blog.makezine.com/archive/2008/03/five_hundred_and_seven_me.html