All of my switches are installed in old metal boxes with no threaded ground screw holes. The boxes are wired using old cloth BX with no ground wire(grounded via casing). Some of the BX wire insulation is crumbling near light fixtures, I think due to heat.

As I replace the light fixtures I'd like to replace the BX from light to box with Romex. The BX that supplies the box is in good shape. How do I appropriately ground the new fixtures. There are no threaded holes in the metal boxes. Grounding to the box via the yoke on new switches will work but I don't think this is proper. Can I just tap a new 10-32 hole in the box? Should I tear out all of the old bx or maybe just run new ground wires? Thanks in advance.

  • I think tapping a new hole in the box is far superior to relying on the sometimes wobbly contact between the yoke and the box. – A. I. Breveleri Nov 11 '17 at 17:59
  • Another problem with using the switch yoke as part of the ground path is that whenever you pull the switch out for maintenance or analysis, the light is no longer grounded. This could add confusion to the analysis of a failure by some future DIY electrician. – A. I. Breveleri Nov 11 '17 at 18:03
  • Another method of grounding to a metal box is the spring clip which holds a ground pigtail hard against the box. grainger.com/product/2DCN3?cm_mmc=PPC – Jim Stewart Nov 11 '17 at 18:03
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    @Jim Stewart: If you can find a reference that indicates that the clip is usually acceptable to electrical codes, this should be an answer. – A. I. Breveleri Nov 11 '17 at 18:06
  • I am deleting my comment advocating using the mounting tab to ground a switch because of the answers in this diy.stackexchange.com/questions/103034/…. Evidently using the plain end tab of a switch for grounding is not allowed for flush mounted metal boxes. It is allowed only for surface mounted metal boxes. Devices labelled "self grounding" (with spring loaded contacts) presumably are allowed even on flush mounted metal boxes. – Jim Stewart Nov 11 '17 at 18:29

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