Power drill caused lights to flicker
This could be a &quot;floating neutral,&quot; which is a serious electrical problem. See this other question here on stackexchange. In my case I resolved the problem by calling the power company. They asked &quot;Do your lights flicker?&quot; They replaced a nearby power pole within a few hours.
You could also have a poor/ineffective electrical ground. Does the drill have a three-pronged plug?