Drawings and parts sketches
Rules for drawing parts drawings
Part drawing. Under the drawing, details are understood as a design document containing the part image and other data necessary for its manufacture and control. Along with the images of the shape of all parts of the part and their dimensions, the working drawing in general also contains the following data:
limiting deviations in the dimensions, shape and arrangement of surfaces, the rules of instructions of which are established in GOST 2.307-2011 and 2.308-79;
designations of surface roughness, established by GOST 2.309-73;
designation of coatings, thermal and other types of processing, established by GOST 2.310-68;
a text part consisting of technical requirements and technical characteristics, inscriptions and tables with dimensions and other parameters, technical requirements, control complexes, symbols, the rules of application of which are established in GOST 2.316-2008.
The specified data on the drawing of parts is applied after studying the courses of machine parts and devices, the fundamentals of interchangeability, technical measurements and standardization, the fundamentals of technology. Therefore, in the course of engineering graphics, the rules for making drawings of parts relating to the image of their shape in the drawing and the application of nominal dimensions are studied mainly.
Let's consider some rules for the implementation of drawings of parts, set by GOST 2.109-73, taking into account the specifics of the learning process.
Working drawings are developed for every detail. It is allowed not to issue drawings for parts manufactured from a shaped or profiled material by a cut at a right angle and from sheet material by cutting along the circumference or along the perimeter of a rectangle without further processing, and also in some other cases established by the standard.
Flexible parts. If the image of a part produced by a flexible one does not give an idea of the actual shape and dimensions of its individual elements, then a partial or full scan is placed on the drawing (see Figure 13.1) . The sweep image only applies dimensions that can not be specified in the image of the finished part.
It is allowed, without violating the clarity of the drawing, to combine the image of the part of the scan with the view of the part. In this case, the sweep is represented as a dash-dot dotted line with two dots with fine lines and the sweep sign is not placed (Figure 15.1).
Details of the spring type. Two kinds of shapes are distinguished for such details: the shape of the part in the free (unstressed) state and the shape of the part in the deformed (stressed) state in the finished product or in the forming tool. The details of these states of the part are taken into account when they are shown in the drawings.
If the dimensions of individual elements in the stressed state are important for the part according to the conditions of assembly of the product or the conditions of the location of the part in the product, and in this state they are measured, then in the drawing a detail is shown in two states (Figure 15.2): in the free state
continuous solid lines and dash-dotted lines with two points after the change of the initial state. The dimensions of the elements that are measured after changing the original shape of the part are applied to an image made with dash-dotted, thin lines with two dots.
If a part in the free state acquires an arbitrary shape (Fig. 15.3, b), which is not installed by the drawing, then this part is represented (Figure 15.3, a) only with the dimensions indicated for the measurement. In this case, the specifications in the drawing field record The dimensions are indicated for the measurement.
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