To the initiated, it sounds obvious enough that a hammer is designed to deliver an impact force to a workpiece with minimal deformation to itself - such as driving a nail into a wooden beam to secure two halves of wooden beam or into a wall as a means to hang a photo frame. As the wood is softer than the nail, it would often time comply and the nail, being a softer metal, would typically deform before the hammer face.

An example of a woodworking hammer can be seen in this Rewin RYJ3570, which usually come with a curved claw to facilitate the removal of nails from wood. In metal fabrication, fabricators would typically use a ball-peen hammer with a hemispherical head to shape metals.

 

A mallet, such as this Rewin WA025 plastic mallet, on the other hand is also designed to deliver an impact force through soft impact blows - without marring or damaging the workpiece such as to fit two pieces of wooden work pieces together or to gentle nudge an aluminium engine case cover (that is only held down by the adhesive nature of the gasket) off the engine block once all the bolts have been removed.

While the rubber mallet, such as the Rewin WJC001, can be used for either woodworking of engine work however the smaller face of a plastic tends to fit into tighter spaces more readily. If a hammer had been used, it would either dent, deform or crack the brittle aluminium engine case covers.

Mallets are typically made from either wood, hardened plastics or hardened rubber. As the face of the plastic mallet is softer than the workpiece, the faces, are also user replaceable should the need occur. Apart from not deforming the end of a chisel, wooden mallets also give better control by reducing the driving force when used to chisel wooden workpieces.

Another variant of the plastic mallet is the dead blow hammer which is hollow and typically filled steel shots which distributes the strike force over a longer period and thus reducing the rebound energy.

The trick to using a mallet on an engine case is to lightly tap and listen to the change in sound from a solid to a hollow sound - which indicates that the sealant or gaskets have separated.