How to read technical drawings

Understanding how to read part drawings is essential to designing a product. Technical drawings, also called mechanical drawings, mechanical working drawings or manufacturing drawings, provide the details needed to manufacture the product being depicted.To get more news about mechanical cad, you can visit shine news official website.
Manufacturing technical drawings are not replacements for 3D CADs, which are excellent representations of products. But they do not provide the information that technical drawings give you. The technical-drawing definition states that it is a precise and detailed drawing. Below is the drawing for a tapered cap, which protects profiles from damage and debris, moisture and liquid ingress during manufacturing, storage and transportation.

Technical-drawing standards
Let’s start with the technical drawing information box on the right-hand side. This is a technical drawing title block example, and tells you the product designer, which in this case is Essentra Components.
All dimensions measured in mm
The figures in the table at the left of the box are in millimetres.

2. Do not scale
This is standard in engineering diagrams and means that you shouldn’t take measurements from the drawing itself. The stated dimensions give you the information you need.

3. Linear Tolerance
Another standard piece of information. Once manufactured, all parts vary slightly in their actual measurements. Linear tolerance is the amount of error acceptable in the dimensions of the product.

Understand how to read tolerances. In the example above, there are three columns. Each column indicates the tolerance of a dimension, depending on the number of decimal places that the dimension has. So the column headed 0 means a dimension with no decimal places, while 0.0 is a dimension with one decimal place and 0.00, a dimension with two decimal places.

As an example, let’s take the dimensions for d1 in the drawing, which is 11.3 mm. The size puts it in the 10-30 mm range. To discover the tolerance, we go to the column headed 0.0, because 11.3 has just one decimal place. The tolerance is therefore more or less 0.20 mm.

4. Third angle projection
The engineering title block also includes the symbol for third-angle projection, meaning that’s the projection in which the cap is shown. Only the U.S., UK, Japan, Australia and Canada use third-angle projection. All other countries use first-angle projection. As you can see, they are mirror images of each other.Third-angle projection tells an engineer that the top view of the product comes above the front view, and the right-side view is drawn to the right side of the elevation. As a comparison, first-angle projection the top view comes below the front view and the right-side view is drawn to left side of the elevation.

5. Angular tolerance
The angular tolerance of a dimension. Like linear tolerances, this tells you how much error is allowed.

6. Unspecified Radii
When radii of bends or fillets (rounding of a part’s corner) are the same, or if any radius is predominant, it’s standard not to draw the radii dimensions on the image. Instead, it’s noted as unspecified radii in the engineering drawing title box.

7. Draft-Angle
A requirement for injection-molding designs. Calculated in degrees, the draft angle is measured from the vertical axis of the mold to account for shrinkage, which is common with thermoplastics. Note, the material shown in the box is LDPE, a popular thermoplastic.

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