What is a group of Washers called?

A group of washers is commonly called a Knob.

A collective noun for washers is a "cluster" or a "pile". These terms describe a group or gathering of washers, denoting them in a compact and organized manner. A cluster of washers brings to mind their counterparts neatly arranged, ready for use or storage. Similarly, the word pile signifies a grouping of washers, perhaps positioned haphazardly or stacked together. Both terms capture the essence of washers existing in unity, indicating their common purpose of serving in various tasks requiring secure fastening or reinforcement.