Metallics JBWSS12 Washers 1/2 Belleville SS (Jar 100)

A Belleville, or conical, washer is a spring washer that flattens under bolt load and keeps tension on the joint as it heats, cools, and the conductor relaxes. The JBWSS12 is specified for load bearing tension type applications, which is the classic use on bolted bus, lug, and grounding connections where a flat washer alone would let the bolt lose clamping force over time.

Crown up, against the nut or bolt head, with the dished side facing the joint so the washer can flatten as you torque. The JBWSS12 is a conical spring washer, not a flat washer, so installing it backwards or stacking it against another spring washer defeats the tension it is there to hold.

Stainless steel. That matters for outdoor gear, wet wells, rooftop equipment, and coastal jobs where a plated carbon steel washer would rust and lose its spring set.

100 washers per jar. It ships as a jar pack, which is the practical quantity for an electrician stocking a service truck or an MRO crib standardizing on one 1/2 inch Belleville across a facility.

They do different jobs. A flat washer spreads load, a split lock washer bites the surface, and a Belleville acts as a spring that maintains bolt tension through thermal cycling. On aluminum conductor and bus connections that heat and cool, the Belleville is what the connection detail usually calls for. Many installations use a flat washer under the Belleville to protect the mating surface, so specify both if your detail shows both.