Petrol engines with reciprocating piston and rotating crankshaft and worn gear shows systems executing pure rotary motion. The engine crankshaft performs rotary motion in one direction, while the piston moves linearly up and down in the cylinder. The hand drill performs reversible rotary motion. That is the handle and the drilling but can move clockwise or anti clockwise as may be required. The same thing applies to the worm gear. This is a device which has a threaded shaft (worm) that meshes with a greater wheel (worm wheel). It is used to transfer rotary motion between shafts that are at right angles to one another
