Callum Hart-Woodcock, of Redcliffs School, asks :-

Is a screwdriver a machine or not?

Barrie Lord, an engineer at Massey University's department of Production Technology, responded.

In order to consider the question as to whether a 'screwdriver is a machine', we must first define what is understood by a machine. The dictionary defines a machine as an assembly of interconnected components arranged to transmit or modify force in order to perform useful work, or a device for altering the magnitude or direction of a force.

Clearly the screwdriver does not fall into the first category, however at a first glance the second definition could describe a screwdriver, as it is a device for concentrating a torque (twisting) force supplied by hand and wrist over a small area of the screw slot face. It could thus be called a simple machine (a one element device). However, simple machines such as the leaver, screw, ramp etc. all produce a change in force (a mechanical advantage) by virtue of a change in force displacement (the velocity ratio) or vice versa. The screwdriver, a device for transmitting torque is not designed with these changes in mind ie., the torque in, and the torque out, are the same, as is the angular displacement.

The screwdriver should thus best be defined as a hand tool,ie a device or instrument, especially one held in the hand for performing or facilitating mechanical operations.