Engineering drawing

An engineering drawing is a type of technical drawing used to share clear information about an object. It helps people understand how something should be built or made. One common use is to show the exact shape and size needed to create a part. This is called a detail drawing. Many drawings are often needed to fully describe even a simple part. These drawings are connected by a "master drawing," known as an assembly drawing. This main drawing lists the numbers of the smaller parts, how many of each are needed, and what they are made from.

Engineering drawings often include several different views of a part, like front, side, and top views. They use special abbreviations and symbols to save space and may also have extra text to explain important details. Only the necessary information is included, such as the exact dimensions of the part. The drawings also show tolerances, which are small allowed differences in size, so the part can be made and still work correctly. Sometimes, more detailed production drawings are made from these engineering drawings to guide the actual building of the part. Every drawing has a special box called a title block. This tells who made the drawing, who checked it, what units were used, and the name and number of the drawing.

History

Technical drawing has helped people share ideas for thousands of years. Ancient groups like the Egyptians and Mesopotamians used drawings to plan buildings and water systems. In ancient Greece and ancient Rome, engineers drew plans for bridges and aqueducts.

During the Renaissance, artists and inventors used better drawing methods. The Industrial Revolution brought new rules to make drawings clearer. Tools like T-squares and protractors helped create exact plans for big projects. Today, computers and computer-aided design (CAD) software make drawing faster, but old ideas are still used.

Standardization and disambiguation

Engineering drawings can be complicated, so standards help everyone understand them the same way. These rules help people from different countries, even if they speak different languages, read and use drawings correctly.

One important set of standards is ASME Y14.5, used a lot in the United States. Another key standard is ISO 8015 (Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules), which is important all over the world. These standards make sure that engineering drawings are clear and the same for everyone to use.

Media

For many years, people made engineering drawings by hand using pencils, pens, and rulers on paper. Now, most drawings are made with computer-aided design, or CAD. Some people still use pencil and paper.

Hand tools for drawing include pencils, pens, straightedges, T-squares, and rulers. There are also special tools like French curves, protractors, and dividers. In the past, people used slide rules for math, but now they use calculators. The phrase "go back to the drawing board" means to start over to fix problems. Today, most engineering drawings are made with CAD, but copies are still often called "blueprints" even though they are usually printed in black ink.

Systems of dimensioning and tolerancing

Engineering drawings show the shape of an object and its sizes. They also show how much the sizes can change. There are different ways to write down these sizes and changes.

The simplest way is to write down distances, like how long or wide something is. These distances have rules about how much they can change.

One method is called coordinate dimensioning. It uses points and lines to describe an object from a starting point, like on a map. Another method is called geometric dimensioning and tolerancing. This helps describe shapes and sizes in a more flexible way.

Common features

Drawings help us learn about objects. They show the shape of an object from different angles, such as the front, top, and side. They also tell us the size of the object using units and what the object is made of.

There are different kinds of lines in drawings. Some lines show edges we can see, while others show hidden edges or special parts like circles. Each kind of line has a different look, like solid lines or dashed lines, to help us understand the drawing.

Conventional parts (areas)

Every engineering drawing has a special area called a title block. This block has important information. It includes the drawing’s title, number, and the name of the company that made it. It also shows the measurement units and any legal notices.

Other important parts of a drawing include a revisions block. This block lists changes made to the drawing. There is also a notes list with extra instructions. The main area of the drawing is called the field. It shows the actual design. Sometimes, there is a list of materials or parts used. This list can be near the title block or in a separate document.

Abbreviations and symbols

Engineering drawings use short names and symbols to make designs easy to read. For example, cold rolled steel is often called CRS, and diameter might be written as DIA, D, or ⌀. These drawings work well in any language because most words are only in the title block, and symbols are used instead of words elsewhere.

With computers now making many drawings, some older symbols are not used as much. This can make it hard to read very old hand-drawn plans, especially from times like World War II, because the meanings of some symbols are hard to find today.

Example

This is an example of an engineering drawing. It shows different line types, each with its own color to make things clear.

• Black lines show the object and its texture.
• Red lines show hidden parts.
• Blue lines show the center of a piece or opening.
• Magenta lines show special lines or cutting planes.

Sectional views are shown by arrows pointing in the direction of the view.

Legal instruments

An engineering drawing is like a legal document. It tells people exactly what to build or make. With a purchase order and other papers, the drawing becomes part of a contract. If the product has problems, the worker or maker is safe if they followed the drawing right. If the drawing has mistakes, the engineer is responsible. This is important because making things can cost a lot of money.

Relationship to model-based definition (MBD/DPD)

For a long time, engineering drawings were the main way to share design details for making products. Now, a new method called model-based definition (MBD) or digital product definition (DPD) is used more often. In MBD, design information is put into special computer programs and used to make products, sometimes without needing a traditional drawing.

Even with MBD, people still use drawings to help make and check products. These drawings come from the design data and are marked as reference only. This means the main design information comes from the computer data, not the drawing.