This is the Upper Armature Assembly for Eaton Cutler-Hammer Size 4 and 5 starters and contactors. If your starter is chattering this is one of the parts needed for the repair.

Chattering Cutler Hammer Repair.

Parts Needed to Repair a Chattering Starter:
Contact Kit: 6-26-2, 6-36-2, 6-36-4, or 6-45-2
Coil: 9-1891-1 (120v), 9-1891-2 (240v), or 9-1891-3 (480v)
Lower Armature Assembly: 48-1030-2
Upper Armature Assembly: 48-1029-4

Replacing these parts will resolve most chattering issues with these starters. Specifically the lower armature assembly wears out and seems to be the worst culprit. We stock all of these parts and even offer a discount when buying them as a kit.