When reading a blueprint, it is essential that you know which elements to look for, and what those elements mean. Manufacturing blueprints are images designed to help the reader understand how to build a particular component or device, and how it works. A draftsperson or designer creates blueprints by hand or using specialized software. They draw blueprints to a particular scale, meaning that the drawings are at a much smaller or much larger size than the actual completed product.

Lay the manufacturing blueprint on a flat surface under a reading light. Many blueprints have very fine lines and are hard to read in low light. Keep a pen and paper close by in case you want to make notes. Make note of the tolerance allowed for the blueprint. Tolerance refers to the amount of difference that may exist between the scale of the blueprint and the actual manufactured part.

Locate and read the information blocks. These blocks include the title and revision blocks that contain the majority of the identification information for the blueprint. These blocks may be on the front page of the blueprint or could be on the blueprint itself. The information blocks contain all identifiers for the blueprint including the name of the component, its surface texture, its intended use, the blueprint number or part number associated with the component, and the company or engineer that designed the component. They also include the revision number for the blueprint as well as the reference and zone numbers to identify where the part will be used after it is manufactured. Scale may also be included in a scale block beside the other information blocks.

Read the materials list. This list should be located on the front page of the manufacturing blueprint. The materials list details every piece of equipment and every component that will be needed to successfully manufacture the component detailed on the blueprint.

Locate the key. Like the legend on a map, you can find the key to a manufacturing blueprint near the edge of the document. The key will tell you to what scale the blueprints were drawn and will give you any other information pertaining to how the blueprint should be read, including measurements and explanation of any symbols used. It also lists what abbreviations are used in the blueprint along with their meaning. In some cases, the key will be located on the front page of the blueprint with additional information about the drawing.

Look at the blueprints as a whole diagram. Understanding the detail in the blueprints requires knowledge of the component being drawn and constructed. Analyze the larger parts of the diagram first and try to understand how they work together.

Scrutinize the detailed parts of the blueprint. Pay special attention to the smaller and more intricate details of the drawing after you have familiarized yourself with the larger segments of the blueprint. These details will be an integral part of the manufacturing process of the component.

Read the lines. Blueprints are composed primarily of drawn lines. Each kind of line has a meaning. For example, a heavy solid line refers to a visible edge of the completed component. A dotted line refers to an interior edge not visible on the exterior of the completed component. Lines ending in arrows are used to show a particular distance, while thin lines that repeat long and short dashes are used to indicate where the center of parts of the component.