What is a divided circle on an assembly drawing that shows a part number and indicates the required quantity of that part?

A divided circle on an assembly drawing that shows a part number and indicates the required quantity of that part is referred to as a balloon. Balloons are commonly used in engineering drawings to visually link parts to their corresponding item numbers in the parts list or bill of materials. This method enhances clarity by associating each component with specific data, such as quantity and part identification, which streamlines communication and reduces the risk of errors during assembly.

The use of balloons is particularly effective in complex assemblies, where many components are involved. They create a quick reference that allows anyone reviewing the drawing to easily identify and obtain further details about each part listed. The distinctive shape of a balloon, often reminiscent of a speech bubble, contributes to its utility in providing visual cues in assembly drawings, making it easier for technicians and assemblers to follow the instructions accurately.