Adjusting blade switch gap--Generally switches should be gapped about 1/16",
but this is not absolute. The gap should be such that when the switch is
fully closed the stationary switch should be perceptively moved. This
ensures pressure on the contacts. The normal action of blade switches
provides a slight sweeping motion between the contacts, which under normal
conditions, will keep the contact points clean.
Note that if you cannot achieve about 1/16" gap and the slight
movement of the stationary switch, you probably have a mechanical binding
problem where something wrong.