any metal device that is not earthed can accept charge from its environment and be energised unhindered. There are many possible sources of charge, in the worst case it is a live conductor that has become detached and that touches the metal (i.e. weak soldering point in the self-soldered spindle connector) and which exposes the user to serious danger; however, other sources such as electrostatic charging, e.g. from dust extraction, can also be the source of such charges on the metal parts. The electrical bonding and earthing, i.e. the bringing together of all metal parts of a device, prevents such charges from building up and thus prevents electric shocks or sparks.