No reason at all for a bearing to be electrically isolated from a case. They
utilized that nylon bushing for their convenience.. assembly method, loose
bore dimension tolerances, potential production change in parts source, etc.
Nearly all motor types have bearings mounted in metal frames, there is no
electrical reason to attempt to isolate the rotor from the case.
Most routers (and various power tools) with metal nose pieces have
pressed-in or snug fitting bearings (some with retainers) fitted into a bore
in the housing.
There are no perfect insulators (nor conductors), so all insulation types
have a minute amount of leakage current. This miniscule leakage level won't
be harmful to the operator or the bearings.
The high rate of fan-blown airflow over a high speed rotor would generate
static (Van Der Graff type effect) likely moreso on a plastic housing.
There is a potential for bearing damage when elevated currents pass thru
bearings in some applications such as a turntable used for welding.
"Bob La Londe" < email@example.com> wrote in message
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