JB/T 7944-2000 This standard is a revision of JB/T 7944-95 "Sampling Inspection of Cylindrical Helical Springs". This standard specifies the sampling method for cylindrical helical springs. This standard applies to cold-rolled and hot-rolled cylindrical helical spring compression, tension springs and cold-rolled cylindrical helical torsion springs. This standard does not apply to valve springs, hydraulic springs, and springs with special requirements such as diesel engine injection pumps, governors, and injectors. This standard was first issued in 1989 as GB 1239.5-89, and the standard number was adjusted to JB/T 7944-95 in 1996. JB/T 7944-2000 Sampling Inspection of Cylindrical Helical Springs JB/T7944-2000 Standard download decompression password: www.bzxz.net

ICS21.160
Standard of the Machinery Industry of the People's Republic of China
JB/T7944-2000
Sampling procedures for inspection by attributes of coiled helical springs2000-04-24 Issued
National Bureau of Machinery Industry
2000-10-01 Implementation
JB/T-7944-2000
This standard is a revision of JB/T7944-95 "Sampling inspection of cylindrical bursting springs". During the revision, the original standard was edited and the main technical content remained unchanged.
This standard replaces JB/T7944-95 from the date of implementation. This standard is proposed and managed by the National Technical Committee for Spring Standardization. The drafting units of this standard: Mechanical Science Research Institute, Tianjin Spring Research Institute. Mechanical Industry Standard of the People's Republic of China
Sampling procedures for inspection by attributes ofcoited helical springs1Scope
This standard specifies the sampling inspection methods for the test column end family springs. This standard applies to cold-rolled and hot-rolled cylindrical helical compression, tension springs and cold-rolled cylindrical helical torsion springs. JB/T7944-2000
Replaces JB/T794495
This standard does not apply to valve springs, hydraulic springs, and springs with special requirements such as injection pumps, governors, and injectors for diesel engines. 2Referenced standards
The provisions contained in the following standards constitute the provisions of this standard by reference in this standard. When this standard is published, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T2828--1987 Batch inspection counting sampling procedure and sampling table (applicable to continuous batch inspection) 3 Defects
Springs that do not meet the technical requirements specified in product technical standards, process documents, and drawings constitute defects. According to the severity of the defects, they are generally divided into:
A defect item (fatal defect);
B defect item (serious defect);
C defect item (general defect).
Spring defect items are shown in Table 1.
Spring category
Cold rolled compression spring
Cold rolled tensile spring
Cold rolled torsion spring
Hot rolled shrinkage spring
Hot rolled tensile spring
A Defective items
Decarburization, hardness
Decarburization, hardnesswwW.bzxz.Net
Dephosphorization, sulfurization
B Defective items
Spring properties, outer diameter or inner diameter
|tt||Diameter, surface acid depression, permanent deformation
Elastic properties, surface defects
Spring properties or internal angle,
Surface defects
Spring properties, outer diameter or inner
Diameter, surface defects, permanent deformation
Elastic properties, surface defects,
Water-resistant deformation
Note: When there are special requirements, the fatigue life can be agreed upon by both parties. Can be used as the monthly inspection form for A defect items Approved by the National Machinery Industry Bureau on April 24, 2000 C defect items
Verticality, total number of surfaces, free height
Uniform hook of pitch
Outer diameter, free length, hook and ring structure
Partial length
Outer diameter or inner diameter, inner length
Torsion length
Vertical point, straightness, free height
Uniformity, total number of turns, pitch uniformity
Outer diameter, free length
Implemented on October 1, 2000
Inspection level
According to the special inspection level S-4 in GB/T2828. 5 Sample size code
JB/T7944—2000
The sample size code is determined according to the batch size of the inspection batch submitted and the special inspection level S-4, see Table 2. Table 2
Inspection water rate
Batch range
91~150
151-500
501~1200
1201~10000
10001-35000
35001~500000
≥500001
6 Sampling plan
6.1A Sample extraction for defective items
6.1.1 Regardless of the size of the delivery batch, the fatigue life samples of cold-rolled cylindrical springs are 4 pieces: metallographic and decarburization samples are 2 pieces, and the manufacturer can also provide 2 test (blocks).
6.1.2 Regardless of the size of the delivery batch, the fatigue life samples of hot-rolled cylindrical helical springs are 2 pieces: the metallographic and decarburization samples can be provided by the manufacturer as 2 test bars (blocks).
6.1.3 When there is a special need, it can be agreed upon by both the supply and demand parties. 6.2BC defect item sample extraction
Depending on the size of the delivery batch, one, two or five normal inspection sampling plans can be adopted. 6.2.1 When the delivery batch is 2~1200 pieces, a normal inspection sampling plan can be adopted, see Table 3. 6.2.2 When the delivery batch is 1201~10000 pieces, a two-time normal inspection sampling plan can be adopted, see Table 4. 6.2.3 When the delivery batch is greater than 10000 pieces, a five-time normal inspection sampling plan can be used, see Table 5. Sample size code
Sample size code
Sample size code
JB/T7944-2000
Sample size
Sample size
Sample size
Note: Samples with the symbol "*" cannot be judged as qualified for the inspection batch. Table 4
Cumulative sample size
Cumulative sample size
Quality level AQL
Quality level AQL
Quality level AQL
7Quality level AQL
7.1A Defective items
JB/T7944--2000
In the inspection, even if there is one spring that fails to meet the quality standards, the corresponding inspection shall be repeated for sampling. If there is still one spring that fails to meet the quality standards during this inspection, the entire batch of products shall be rejected. 7.2B Defective Items
Qualified Quality Level is 4.0.
7.3C Defective Items
Qualified Quality Level is 6.5.
8 Others
8.1 The manufacturer has the right to use any inspection procedure to control quality during the production process (including finished product warehouse acceptance inspection), but must ensure that the quality of the finished spring products meets the requirements of this standard and the relevant standards. 8.2 When the purchaser considers it necessary or economically reasonable, it may exempt the inspection of the products submitted for acceptance based on the quality reputation of the manufacturer and the quality assurance of the products previously delivered, or it may conduct acceptance inspection according to the sampling plan agreed by both parties. 8.3 The acceptance inspection items of spring products are limited to the relevant indicators specified in the relevant standards. The purchaser should focus on whether the products can meet the expected use requirements. Therefore, it can increase or reduce the random inspection items according to the specific use requirements. 8.4 When there is a dispute over the products submitted for acceptance, the purchaser must give the manufacturer an opportunity to verify. 8.5 The manufacturer must classify or repair the rejected product batches before resubmitting them for acceptance.
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