Understanding Parts and Assembly Drawings: a guide for students

High school Design and Technology students are often required to understand, interpret, and produce assembly drawings. These are technical drawings that show how various parts of a product fit together.

Guidelines for assembly drawings

• Each part is given a number, usually inside a circle with a leader line;
• A parts list is added to identify each component within the drawing with an item number, description, quantity, material and other necessary comments (see below);
• Overall dimensions are usually indicated;
• The drawing should be sectional if internal assemblies are involved;
• Two types:
  • Fitted assembly drawings (shows parts in assembled form);
  • Exploded drawings (show the components pulled apart along an axis).

Parts lists

A parts list is a comprehensive list of all components required to assemble a product. Parts lists are usually positioned in the bottom right corner of the drawing or above the title block, arranged in a clear tabular format. The item numbers should be numbered consecutively starting from 1, and standard or catalog parts (like screws, nuts, or other fixings) are typically listed last. The parts list may be oriented either horizontally or vertically on the drawing sheet, though horizontal orientation is more common for easier reading. Each component should be listed only once, even if it appears multiple times in the assembly, with the quantity column indicating the total number required.

Cutting lists

Assembly drawings sometimes include cutting lists. A cutting list details the raw material requirements for parts that need to be cut to size. This is helpful for projects where raw materials need to be cut to specified sizes before assembly.

Cutting lists provide crucial fabrication information that complements the assembly process. For instance, if you’re building a wooden cabinet, the assembly drawing shows how it goes together, the parts list identifies all components, and the cutting list specifically details the dimensions of wood pieces needed to be cut from stock material.