Tolerance and Cooperation Plan 2

Labeling of tolerances and fit

Tagging Method on part drawings

The dimensional tolerances on a part drawing can be marked in the following three forms:

1) Add the public difference band code to the right of the basic size. For details, see.

2) the maximum deviation is injected to the right of the basic size. For details, see B.

3) on the right side of the basic size, the difference band code and the corresponding limit deviation are injected. But the limit deviation should be enclosed in parentheses, see c.

When the limit deviation is indicated, the decimal points of the upper and lower deviations must be aligned, and the digits after the decimal points must be the same; when the deviation or lower deviation is "zero", use the number "0" to mark (without plus positive or negative signs) and align with the single digit before the upper or lower deviation; when the difference band is symmetric with the basic size, that is, the two absolute values of the deviation are the same, only one note is required for the deviation, and the symbol "Shi" should be injected between the deviation and the basic size ", the height of the two numbers is the same.

Annotation Method on assembly drawing

When there are coordination requirements for the two combined parts on the assembly drawing, the corresponding coordination code should be injected on the right side of the basic size. The injection form is one of the three forms.

 

 

 

 

 

 

 

 

 

 

Shape and location tolerances

Basic concepts of shape and location tolerances

After the parts are processed, there will be not only dimensional errors, but also errors in geometric shapes and locations. As shown in, even when the size of the cylinder is qualified, one end may be large, the other end is small, or the middle thin ends are thick, and the cross section may be not circular, this is a shape error;

As shown in the following figure, the step axis may be different from the axis of each axis segment after processing, which is a location error.

Therefore, shape tolerances refer to the allowable variation of the actual shape on the ideal shape. Location tolerances are the allowable changes to the ideal location for the actual location. The two are short for form-bit tolerances.

Name and symbol of tolerance items

 

 

 

 

 

 

 

 

Tolerance code

1. Code Composition

See for the tolerance code. It consists of the following content:

 

2. Code Description

The tolerance frame is drawn with solid lines and divided into two or multiple grids as needed. The height of the numbers and letters in the frame should be the same as that of the size number in the drawing, the line between the guide line and the reference symbol is drawn with a fine solid line, and the reference symbol is expressed with a short line (2b). The frame length can be determined as needed. See.

 

Dimension of tolerance

(1) connection method between the guide line in the Code and the tested element when the tested element is a line or surface, the arrow of the guide line shall refer to the contour line or its extension line of the element, and shall be clearly staggered with the dimension line, see.

(2) When the element to be tested is an axis or central plane, the arrow of the guide line should be aligned with the dimension line of the element. See figure B on the right.

C \ when the elements to be tested are the public axis and public center plane of each element, the front of the guide line can be directly indicated on the axis or central line. See Figure c on the right.

 

 

 

 

 

(2) For the location tolerances, you also need to use the benchmark symbol and line to indicate the benchmark elements of the tested elements.
Method for connecting benchmark elements:

When the reference element is a prime line and a surface, the reference symbol should be marked by the contour line near the element or its guide line, and should be obviously staggered with the dimension line, see.

When the datum element is an axis or central plane, the datum symbol should be aligned with the dimension line, see B.

When the reference element is the public axis and public center plane of each element, the reference symbol can be directly located near the public axis or the central line. See section C.

(3) When the benchmark symbol is not directly connected to the frame, the benchmark code is used for marking. The method for marking the benchmark symbol is basically the same as that for using the benchmark symbol, in this case, the frame type must be 3 or multiple, and the letter of the reference code is entered. See.

 

(4) When the two elements of the positional tolerances, the tested elements and the benchmark elements can be exchanged, that is, the baseline symbol is no longer drawn when the benchmark elements are selected, and the two sides are represented by arrows. See.

 

 

 

(5) When the same element to be tested has multiple Tolerance requirements and the labeling method is the same, you can draw these boxes together and share a guide arrow. See.

 

 

(6) If multiple tested elements have the same location tolerances (individual or multiple, you can draw multiple arrows on the guide line derived from the box and connect them to the tested elements, as shown in.

 

(7) If the tolerances of any length (or range) of the tested elements are to be given, the labeling method is shown in Figure. For example, the tolerance value of the length (or range) of the element to be tested must be given, and the tolerance value within the full length (or entire element) of the element to be tested must be given. For the labeling method, see B.