机械专业英语阅读教程

Engineering drawing is not only the province of the draftsperson. It is the language of the engineer. It is their means of developing and recording their ideas, and conveying them to others. Every engineer will be using and referring to some form of drawings almost every day. They will often be producing or directing the preparation of drawings. Usually, they make the preliminary sketches and design drawings in accordance with principles of engineering drawing, because this is the most unambiguous way to convey and record information. It is also likely that every engineer at sometime will be checking the work of designers and drafters and approving drawings before they are sent to manufacturing. When engineers sign off the final approval of a drawing, they take responsibility for it. An overlooked error in the drawing could be costly. So a drawing must be true and complete statement of the figure, dimension and technical requirements, expressing the way that the part is to be manufactured. Mechanical drawing is a process which relies heavily upon research in the principles of representation, interpretation and related technical standards. Typical drawings in machine manufacturing are classified as part drawings and assembly drawings. Detailed introducing is as followed

(1)Part drawings

Part drawings are frequently used as instruction fo manufacture and inspection of the parts. An integrated part drawing should include a set of drawings, overall

dimensions, necessary technical requirements and full contents of title block.

A set of drawings: some representation can be given to properly show the internal and external shape of the part.

Overall dimensions: specifying the requirements for manufacture and inspection of the part integrity .

Necessary technical requirements: codes, symbols and notes are used to describe the essential technical requirements in the process of manufacture, inspection and assembly, such as surface roughness, tolerance, heat treatment,case treatment and the like.

Full contents of title block: including the part name, materials, drawing number, scale and signature of responsible individual.

Assembly drawings are used in explaining machines or components. In mechanical design, part drawings are usually related to the assembly drawing which indicates the working principle and structure of a machine or component. In the process of machine manufacturing, the drawinings are to allow machining of the metal based on the part drawing and assembling to create a unit or a machine in due course as well as in operation and maintenance. 2. Representation of machine elements Mechanical drawings in national standards are restricted to those which specify the view, sectional view and broken sectional view to represent the structures and shapes.

Views are projection drawings of the object. Typical views include basic views, directional views, partial views and oblique views. Basic views include upward view, front iew, vertical view, right view, left view and back view, as shown in Fig. 1-2-1. The number of views is always six, four and three, four is the typical views.

Fig 1-2-1Basic views

Sectional views are used to show the internal structure of the object with a dash line. When parts have complex internal geometries, knowing the interior is as important as knowing the exterior, you can use sectioning technique to cut sections' across the object to show internal details.We divide sectional views into full sectional views, half sectional views and partial