Thomas & Betts Insulated Chase Nipple

A chase nipple joins two enclosures or a box to a fitting through a knockout, male threads through the hole and a locknut on the inside pulling it up tight. The Thomas & Betts insulated version adds a thermoplastic insulating throat so conductors pulled through are not cut on the metal edge, which is what you want where the nipple is in the conductor path rather than just bonding two boxes.

Malleable iron. That is the heavier-duty body you would specify for larger trade sizes and commercial or industrial raceway work, as opposed to a stamped steel or die cast fitting.

If the nipple is only tying two enclosures together and no conductors pass through it, a plain chase nipple is enough. If wires run through the opening, the insulated throat on the Thomas & Betts 1944 series protects the conductor insulation at the bushing edge, which is the usual reason inspectors want the insulated version on a conductor pull.

Each is sold as the nipple itself. A chase nipple is secured with a separate locknut on the inside of the enclosure, so plan on a matching trade size locknut for every nipple you order, 1 inch through 6 inch to suit the size you pick.