Part one
1 parts
This kind of parts usually have a shaft, bushing and other parts, in view of expression, just draw a basic view plus appropriate sections and dimensions, you can put its main shape characteristics and local structure express. In order to facilitate the processing of pictures, according to the horizontal projection axis, the best choice for the position of the vertical axis side.
In the labeling of parts size, often with its axis as the radial dimension benchmark. The system shown in Figure 14, with the diameter of 11 (see section A-A). This put the process based on design requirements and processing (the shaft machining in lathe, both ends with thimble to resist center hole axis) unified. And the length of the direction of the reference often choose an important end face, contact surface (axis shoulder) or processing surface, etc..

As shown in the figure of the surface roughness is Ra6.3 of the right shoulder, the main dimension benchmark was chosen as the direction of the length of the 13, 28, 1.5 and outjection 26.5 dimensions; then based on the auxiliary shaft end for the right length, which marked the axis length of 96.
2 cover parts
The basic shape of this kind of parts is disc flat, generally end cover, valve cover, gear and other parts of the main structure, they generally have a revolving body, the local structure often with various shapes, uniform hole and flange rib etc.. In view of the selection, the general selection section view of symmetry or the axis of rotation as the main view, also need to add other appropriate views (such as the left view and right view or view) the shape of the parts and uniform expression structure. As shown in the figure, a left view is added to express the square flange with rounded corners and four evenly distributed through holes.

When the size of the plate cover type part is marked, the axial hole is usually used as the radial dimension datum, and the main dimension datum of the length direction is often used as an important end face.
3 fork parts
These parts generally have a fork, connecting rod, bearings and other parts. Due to their changing processing position, the main consideration of the position and shape of the main view is to choose the main view. For other views of choice, often requires two or more than two basic views, and also with the appropriate part of the local view, numerical control WeChat cncdar section map and other expression methods to express the parts of the local structure. The view selection scheme is concise and clear for the expression of bearing and rib width, the right view is not necessary, and for the T shape rib, the section is suitable.

In marked fork parts size, usually choose symmetry plane of installation or parts as a size standard. See figure method.
4 box parts
Generally speaking, the shape and structure of this kind of parts are more complex than those of the previous three parts, and the change of machining position is more. This kind of parts generally have the body, pump body, reducer and other parts of the body. When selecting the main view, the main consideration of the work position and shape characteristics. The other view, should according to the actual situation of the appropriate section, cross section, local view and oblique view and other auxiliary views, with clear expression of internal and external structure parts.

In the dimension, usually choose the design requirements of the axis, the important installation surface, contact surface (or processing surface), the main structure of the body of a certain structure (width, length), as the size of the benchmark. On the case of the need for machining parts, should be as easy as possible to facilitate processing and inspection requirements to mark the size.
A method for the size of the common structure of 5 parts
Dimensioning of common hole (hole, threaded hole, hole, countersink hole); dimensioning fillet.


The second part
1 introduced the concept of surface roughness and the main evaluation parameters
(1) the concept of surface roughness
The micro geometry of the part surface, which is composed of a small interval of peak and valley, is called the surface roughness. This is mainly in the processing of parts, the surface of the metal knife and cutting tools in left split parts on the surface of the plastic deformation formed. Surface roughness is a technical index and evaluation of the surface quality of the parts, are WeChat cncdar on CNC parts with properties, working precision, wear resistance, corrosion resistance, sealing, appearance etc.. Under the premise of ensuring the performance of the machine, in order to obtain the corresponding parts surface roughness, should be based on the role of parts, select the appropriate processing methods, as far as possible to reduce production costs. Generally speaking, where the parts with the requirements of the relative movement of the surface, the surface roughness parameter values to be small.
(2) code, symbol and mark of surface roughness
131-1993 GB/T provides the surface roughness code and its injection method. The symbol that represents the surface roughness of the part is shown in the following table.

(3) the main evaluation parameters of surface roughness
1) the arithmetical mean deviation of the profile (Ra) - in the sampling length, the absolute value of the contour offset of the arithmetic mean value. Ra value and sample length see table I.
2) the maximum height of the profile (Rz) - in the sampling length, contour lines and contour line peak peak distance.
Ra parameters are preferred when using.

2 marking requirements for surface roughness
(1) examples of surface roughness code label
The surface roughness height Ra, Rz, Ry parameters by numerical code marked in, besides the parameters named Ra can be omitted, the rest of the parameter values before the need to mark the corresponding parameter named Rz or Ry label samples shown in the table below.

surfaceThe direction of numbers and symbols in the roughness of the surface roughness

(2) the method of marking the surface roughness (symbol) on the drawing
(1) surface roughness generation (symbols) are generally in the visible contour line, the size of the line or their extension line, the symbol of the point of the surface must be from the material to the surface.
(2) the direction of numbers and symbols in the surface roughness code must be marked in accordance with the regulations.
3 examples of surface roughness
In the same pattern, each surface is generally marked only once, and as close as possible to the size of the line. When the space is small or inconvenient, it can lead to. When all the spare parts with the same surface roughness requirements, can be marked in the upper right corner of the pattern, WeChat cncdar CNC parts when most of the surface with the same surface roughness, and the most used a generation (Fu), can also note in the upper right corner of the drawing, add the remaining " or " " " all of the word. Where uniform marked surface roughness generation (symbol) and the description of the text, the height should be 1.4 times the size of the design.

The parts on continuous surface, repetitive elements (such as holes, teeth and grooves) surface and connected with a discontinuous surface with thin lines, the surface roughness generation (Fu), only once

The same surface with different surface roughness requirements, application of thin lines to draw its boundaries, and surface roughness and outjection corresponding size.

Gear, thread and other working surface did not draw tooth (teeth) shape, the surface roughness generation (symbol) number note method.

The working surface of the center hole, the working surface, keyway chamfer, fillet surface roughness can simplify annotation.

Need to be part of local heat treatment or partial plating (coating) coatings, application of coarse dashed line draw its range and marking the corresponding size, can also be the requirement to write in the line of surface roughness symbols on the long side.