If she felt it in her hands then you have a stator connection that is shorted to the chassis ground / body of the drill.
Hold on for some Electrical Engineering explanation
When a magnetic field “collapses” around a coil it creates a VERY high voltage spike. You car coil makes a field off 12volts, but when the points break the connection the field falls and you get a HUGE voltage spike that is sent to the spark plugs... and you sure can feel those.
this same thing is going on as the motor turns the connections to each coil in the motor is engerized until the motor turns and then the field collapse creating that voltage spike.
when it’s shorted via a brush to the chassis somehow... OUCH !!!
Car coils produce around 40k volts at extremely low amps (the amp’s are what kill you, the volts are required to jump surfaces).
Doesn't cordless drills have a dynamic brake? How does it work? Does anyone really know?
