I framed up a steel stud partition wall on the first floor and used plastic bushings to protect the nm across the studs but the feed comes through the floor from the basement. First I drilled out a 1inch hole in the steel bottom plate then used a half inch bit to drill through the floor so even as the nm comes through the floor, it can't directly touch the metal edges. Is there a special bushing or method for protecting the wiring in this case?