Mechanical Drafting Primer


Sample machined fixture for mounting an optical assembly. Scroll down to see a drawing of this part.

Although modern mechanical engineering relies extensively on 3D CAD programs for design, engineering drawings still rule the day for manufacturing and documentation control. Even when a 3D file is used directly by a manufacturer, the drawing is still used to relay important information such as material types, part markings, tolerances, and more.

Everything begins with the 3D model that represents the part we need to produce. We do not typically create a drawing for the part until there is a need. In most cases its because we need to have the part manufactured.

Mechanical Drafting Services

Here at Zalaco, we can provide drawings for any type of part that you need to have produced. Whether its re-creating legacy drawings from old documents, reverse engineering existing components, detailing a partially complete design, or starting from a blank piece of paper – we can help.

Detailed Fabrication Drawings

This is the core of mechanical drafting. The goal is to clearly communicate what we need to a potential supplier. Good engineering drawings help you get quotes back faster. They also ensure that your supplier understands exactly what you need and no one gets a surprise down the road. These drawings include all of the information necessary to manufacture the part – dimensions, tolerances, materials, finishes, and any other appropriate information.

This includes drawing for machined parts, molded parts, sheet metal parts, formed parts, and castings.

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Reduced Information Drawings

Reduced information drawings (“build to model”) rely on the 3D CAD file to minimize the information a drawing needs to contain. Imagine a complex molded part that would take multiple drawing sheets and many views to fully detail. Instead of identifying every dimension, we add a drawing note calling out the 3D model and giving a general tolerance for the entire part. This reduces the drafting expenses up front and generally makes the supplier’s life easier as well.

In almost all cases, you are much better off with a simple one-sheet drawing to go with any 3D CAD file. It lets us specify other information that’s important to the part, give the overall dimensions, and have the drawing in a format (PDF) that anyone can review.

Assembly Drawings

In mechanical drafting, assembly drawings show us how two or more parts are put together. They typically contain a BOM (bill of material) that shows all of the component part numbers that make up the assembly. It’s common that they show one or several exploded views, depicting how the parts go together. Notes with screw torque values or other assembly specific instructions may be included as well.

What Does an Engineering Drawing Look Like?

Here is a simple fabrication drawing of aluminum mount. Actual drawings out output to PDF. Click the picture of the drawing below to download a PDF version, or just click here.

Drawing sample of machined part

Mechanical drafting drawing sample

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