Sanitary Valve Introduction to blanks

The code for the dimensional tolerance of sanitary valve blank castings is CT, and the tolerance grades are divided into 16 grades. The tolerance values ​​of each grade are listed in Table 1. 4.2 The wall thickness dimensional tolerance can generally be selected by reducing one grade. That is, if the general dimensional tolerance on the drawing is CT10, the wall thickness tolerance is CT11. 4.3 Position of tolerance zone

The tolerance zone should be set symmetrically with the basic size of the sanitary valve blank casting as the zero line. That is, half of the tolerance value shown in Table 1 is the upper deviation, and the other half is the negative value as the lower deviation (see Figure 2). For example: when the dimensional tolerance of the sanitary valve blank casting is selected as CT9, the tolerance of the basic size 50 of the sanitary valve blank casting is ±1.

When the sanitary valve blank casting has an inclined part, its dimensional tolerance should be marked symmetrically along the inclined surface (see Figure 4). The tolerance value is selected from Table 1 according to the basic size of the sanitary valve blank casting.

1. Dimensional tolerance of sanitary valve blank castings (GB 1464-86>

The dimensional tolerance of sanitary valve blank castings (code "CT") is divided into 16 grades, see Table 8-2-2. The wall thickness dimensional tolerance can be lowered by one level compared to the general dimensional tolerance. The tolerance band should be symmetrical to the basic size setting of the sanitary valve blank casting.

The mismatch (mismatch) value must be within the tolerance specified in Table 8-2-2. When the mismatch value needs to be further restricted, its value should be selected from Table 8-2-3. The dimensional tolerance grades of batch and sanitary valve blank castings are shown in Table 8-2-40

2. Sanitary valve blank castings Machining allowance of blank castings (GB/T11351-89>

Machining allowance of blank castings of sanitary valves (code "MA") is divided into 9 grades: A, B, C, D, E, F, G, H and J. The values ​​of machining allowance are shown in Table 8-2-5. For batch and mass production of sanitary valve blank castings, the machining allowance grade is selected according to Table 8-2-6.

Instructions for selecting machining allowance of blank castings of sanitary valves:

(1) The basic size should be based on the maximum basic size on the surface with processing requirements and the distance between the surface and its The larger dimension between the machining base dimensions is determined. The basic dimension of the rotating body is the larger dimension of its diameter or height (length).

(2) Each column in Table 8-2-5 has two machining allowance values. The upper value is the machining allowance value for single-sided machining based on one side. The lower value is the machining allowance value for each side when double-sided machining is performed. The schematic diagrams of single-sided and double-sided machining are shown in Figures 8-2-8 and 8-2-90

(3> For sand castings, the machining allowance grade of the top surface (relative to the pouring position) is higher than that of the bottom and side surfaces. For example: the dimensional tolerance is CT10, the machining allowance for the bottom and side surfaces is MA-G, and the top surface is MA-H.

(4) When the machining allowance grade used for the bottom and side surfaces of sand castings is the coarsest grade among all the machining allowance grades corresponding to the selected dimensional tolerance grade, the machining allowance grade for the top surface needs to be the same machining allowance grade as the bottom and side surfaces, corresponding to the dimensional tolerance being reduced by one level. For example: the machining allowance for the bottom and side surfaces is CT10, MA-H, and the machining allowance for the top surface is CT11, MA-H. -H grade.

(5) The machining allowance grade of the sand casting hole can be selected from the same grade as the top surface.

Figure 4 Dimensional tolerance zone of the inclined part

4.4 Misalignment (misalignment) value

The misalignment must be within the tolerance value specified in Table 1. The value is selected from the smaller value in Table 1 or Table 2, and shall not be added to the value listed in Table 1.

Note: ① The tolerance value given in this table includes the tolerance increment caused by the influence of the parting surface, the mold and the core assembly, but does not include the tolerance increment caused by the draft angle.

② The basic dimensions of the sanitary valve blank castings with CT13 to CT16 less than or equal to 16mm need to be marked separately, which can be increased by 2 to 3 grades.

Table 2 Misalignment value

Note: The misalignment value can be agreed upon by the supply and demand parties when necessary.

5. Selection of tolerances for sanitary valve blank castings

5.1 The dimensional tolerances of sanitary valve blank castings are selected from Table 1 according to the grade range specified in Table 3. Generally, they should not exceed the provisions of Table 3.

Table 3 Tolerance grades for dimensional tolerances of sanitary valve blank castings

Note: The tolerance grades in Table 3 are applicable to basic dimensions greater than 25mm. For basic dimensions of sanitary valve blank castings less than or equal to 25mm, the following more refined tolerance grades are usually adopted:

① When the basic dimension of the sanitary valve blank casting is less than or equal to 10mm, its tolerance grade is increased by 3 grades. ② When the basic dimension of the sanitary valve blank casting is greater than 10mm to equal to 15mm, its tolerance grade is increased by 2 grades. ③ When the basic dimension of the sanitary valve blank casting is greater than 16 to equal to 25mm, its tolerance grade is increased by 1 grade. 5.2 Selection of tolerance grade 5.2.1 Gray cast iron sanitary valve blank castings 5.2.1.1 Sand mold manual molding

The mating surfaces of the machine base, end cover, inner and outer bearing covers are selected according to CT10, and the remaining parts and other parts

The dimensional tolerance grade is selected according to CT11, and the tool parts are selected according to CT12. 5.2. 1.2 Sand mold machine molding and shell mold

The dimensional tolerance grade of sanitary valve blank castings is selected according to CT9. 5.2.2 Light metal alloy sanitary valve blank castings

The dimensional tolerance of sanitary valve blank castings of motor light metal alloy parts is selected according to different casting process methods, and the highest CT grade is selected in Table 3. 5.2.3 Copper alloy sanitary valve blank castings

The dimensional tolerance of the mechanical processing parts of copper alloy sanitary valve blank castings is selected according to different casting process methods. The lowest CT grade is selected in Table 3. The processing dimensional tolerance of the unprocessed sanitary valve blank is selected according to the highest CT grade.

6. Marking of dimensional tolerances of sanitary valve blank castings on drawings

6.1 When the dimensional tolerances of sanitary valve blank castings of motor parts meet the requirements of Articles 5.2.1, 5.2.2, 5.2.3 and Articles 4.2 and 4.3, the marking on the drawings can be omitted.

6.2 When the dimensional tolerances of sanitary valve blank castings of motor parts have the following special requirements, they must be marked on the drawings. a The dimensional tolerances of sanitary valve blank castings are set asymmetrically;

b The dimensional tolerance grade of sanitary valve blank castings does not meet the requirements of Article 5.2; c The dimensional tolerance of sanitary valve blanks that are not to be processed is selected to be the highest grade of CT.

6. Marking of dimensional tolerances of sanitary valve blank castings on drawings

6.1 When the dimensional tolerances of sanitary valve blank castings of motor parts meet the requirements of Articles 5.2.1, 5.2.2, 5.2.3 and Articles 4.2 and 4.3, the marking on the drawings can be omitted.

6.2 When the dimensional tolerances of sanitary valve blank castings of motor parts have the following special requirements, they must be marked on the drawings. a The dimensional tolerances of sanitary valve blank castings are set asymmetrically;

b The dimensional tolerance grade of sanitary valve blank castings does not meet the requirements of Article 5.2; c Further restrictions on the mismatch value are required; d There are special requirements for wall thickness tolerance.

5.3 The dimensional tolerances of sanitary valve blank castings with special requirements are generally marked directly on the drawings, and the maximum mismatch value can be stated in the technical requirements.

4.1 Code, grade and value of dimensional tolerance of sanitary valve blank castings

The code of dimensional tolerance of sanitary valve blank castings is CT, and the tolerance grade is divided into 16 grades. The values ​​of each grade are listed in Table 1. 4.2 The wall thickness dimensional tolerance can generally be selected by reducing one grade. That is, if the general dimensional tolerance on the drawing is CT10, the wall thickness tolerance is CT11. 4.3 Position of tolerance zone

The tolerance zone should be set symmetrically with the basic size of the sanitary valve blank casting as the zero line. That is, half of the tolerance value shown in Table 1 is the upper deviation, and the other half is the negative value as the lower deviation (see Figure 2). For example: when the dimensional tolerance of the sanitary valve blank casting is selected as CT9, the tolerance of the basic size 50 of the sanitary valve blank casting is ±1.

When the sanitary valve blank casting has an inclined part, its dimensional tolerance should be marked symmetrically along the inclined surface (see Figure 4). The tolerance value is selected from Table 1 according to the basic size of the sanitary valve blank casting.

Figure 4 Dimensional tolerance band of inclined parts

4.4 Misalignment (misalignment) value

The misalignment must be within the tolerance value specified in Table 1. The value is selected from the smaller value in Table 1 or Table 2, and shall not be added to the value listed in Table 1.

Note: ① The tolerance value given in this table includes the tolerance increment caused by the influence of the parting surface, the mold and the core assembly, but does not include the tolerance increment caused by the draft angle.

② The basic dimensions of sanitary valve blank castings with CT13 to CT16 less than or equal to 16mm need to be marked separately, and can be increased by 2 to 3 levels.

Table 2 Misalignment value

Note: The misalignment value can be agreed upon by the supply and demand parties when necessary.

5. Selection of tolerances for sanitary valve blank castings

5.1 The dimensional tolerances of sanitary valve blank castings are selected from Table 1 according to the grade range specified in Table 3. Generally, it should not exceed the provisions of Table 3.

Table 3 Tolerance grades for dimensional dimensions of sanitary valve blank castings

Note: The tolerance grades in Table 3 are applicable to basic dimensions greater than 25mm. For basic dimensions of sanitary valve blank castings less than or equal to 25mm, the following more precise tolerance grades are usually adopted:

① When the basic dimension of sanitary valve blank castings is less than or equal to 10mm, its tolerance grade is increased by 3 grades. ② When the basic dimension of sanitary valve blank castings is greater than 10mm but equal to 15mm, its tolerance grade is increased by 2 grades. ③ When the basic dimension of sanitary valve blank castings is greater than 16 but equal to 25mm, its tolerance grade is increased by 1 grade. 5.2 Selection of tolerance grades 5.2.1 Gray cast iron sanitary valve blank castings 5.2.1.1 Manual sand mold molding

The mating surfaces of the machine base, end cover, inner and outer bearing covers are selected according to CT10 grade, and the remaining parts and other parts

The dimensional tolerance grade is selected according to CT11 grade, and the tool parts are selected according to CT12 grade. 5.2. 1.2 Sand mold machine modeling and shell mold

The dimensional tolerance grade of sanitary valve blank castings is selected according to CT9. 5.2.2 Light metal alloy sanitary valve blank castings

The dimensional tolerance of sanitary valve blank castings of motor light metal alloy parts is selected according to different casting processes, and the highest CT grade is selected in Table 3. 5.2.3 Copper alloy sanitary valve blank castings

The dimensional tolerance of the mechanical processing part of the copper alloy sanitary valve blank casting is selected according to different casting processes. The dimensional tolerance of the unprocessed sanitary valve blank is selected according to the highest CT grade.