Grounding Bushing?

[dduffee260]

When do most of you install grounding bushings on conduit or nipples? I have been told if you knock the hole out yourself then it does not need a grounding bushing. Only if the hole has a concentric knockout.
I know alot of contractors use plastic bushings because they are cheaper, then some are so cheap they don't use any bushings at all. When is a grounding bushing required by code?

 

[bphgravity]

Perform a search on this forum. This has been discussed to death here.

In the meantime, review 250.92(B) and 250.96(A) depending on whether you are talking about the supply or load side of a service.