Some standard content:
GB/T 3177-1997
This standard is revised from GB3177-82 with reference to the draft international standard ISO/DIS1938-3 "Smooth workpiece dimension inspection Part 3: Inspection guide using workshop gauges" and considering the implementation of GB3177. In this way, my country's "Smooth workpiece dimension inspection" standard is based on the consistency with the international standard inspection principles, which can not only ensure the quality of workpiece dimension inspection, but also adapt to my country's process and testing level.
Compared with GB3177-82, this standard has the following major changes: a) The standard applies to workpiece tolerance grades ranging from IT6 to IT18, changing the original standard's provisions that the workpiece tolerance value is greater than 0.009~3.2mm.
b) The maximum size of the applicable workpiece is changed from 1000mm to 500mm. c) In order to meet the needs of dimensional inspection, two methods are given for the acceptance limit, changing the original standard's single method of full indentation. d) The standard gives the safety margin A value and the measurement uncertainty ui value of the measuring instrument in the form of a basic size segment and a tolerance grade list, and gives the u value in grades I, I, and I according to the measurement capability, changing the original provisions of giving the A value and the value according to the workpiece tolerance segment. e) Added three appendices: the confidence probability of measurement uncertainty, the evaluation of the probability of misjudgment and the acceptance quality; and the error rate caused by the workpiece shape error.
Appendix A of this standard is the appendix of the standard. Appendix B and Appendix C of this standard are both suggestive appendices. This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee on Tolerance and Fit Standardization. The drafting units of this standard are: Mechanical Science Research Institute of the Ministry of Machinery, Northeastern University, Wuhan Machinery Industry Bureau, China Institute of Metrology, Shanghai Compressor Factory, Liaoning Provincial Technical Supervision Bureau. The main drafters of this standard are: Li Xiaopei, Li Chunfu, Yu Hanqing, Huang Guojun, Wei Herong, Chen Zuomin, Liang Chunyu. This standard was first published in 1982.
1 Scope
National Standard of the People's Republic of China
Inspection of plain workpiece sizes
Inspection of plain workpiece sizesGB/T3177--1997
Replaces GB3177-82
This standard specifies the acceptance principles, acceptance limits, allowable values of measurement uncertainty of measuring instruments and true selection principles of measuring instruments for the inspection of smooth workpiece dimensions.
This standard is applicable to the inspection of the dimensions of smooth workpieces with tolerance grades of 6 to 18 (IT6 to IT18) and basic dimensions up to 500 mm indicated on the drawings using common measuring instruments such as vernier calipers, micrometers and comparators used in workshops. This standard is also applicable to the inspection of general tolerance dimensions. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were 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/T1800.11997 Fundamentals of limits and fits Part 1: Vocabulary GB1800-79 General introduction to tolerances and fits Standard tolerances and basic deviations GB/T4249-1996 Principles of tolerances
3 General
3.1 Acceptance principles
The acceptance method used should only accept workpieces that are within the specified size limits. 3.2 Basis of acceptance methods
Since both measuring instruments and measuring systems have inherent errors, no measurement can measure the true value. In addition, most measuring instruments are usually only used to measure dimensions, and do not measure possible shape errors on the workpiece. Therefore, for dimensions that comply with the inclusion requirements, the complete inspection of the workpiece should also measure shape errors (such as roundness and straightness), and combine the measurement results of these shape errors with the measurement results of the dimensions to determine whether the various parts of the workpiece surface exceed the maximum entity boundary. Considering the actual situation in the workshop, usually: the shape error of the workpiece depends on the accuracy of the processing equipment and process equipment; the qualification of the workpiece is judged by only one measurement; the temperature, indentation effect, and the systematic errors of the measuring instruments and standard instruments are not corrected. Therefore, any inspection may have misjudgment. In order to ensure the quality of acceptance, this standard specifies the acceptance limit, the allowable value of the measurement uncertainty of the measuring instrument, and the principle of selecting the measuring instrument.
3.3 Standard temperature
The standard temperature of the measurement is 20℃.
If the linear expansion coefficient of the workpiece and the measuring instrument is the same, as long as the measuring instrument and the workpiece are kept at the same temperature during measurement, it can deviate by 20℃.
4 Acceptance limit
The acceptance limit is the size limit for judging whether the workpiece is qualified or not when inspecting the size of the workpiece. Approved by the State Bureau of Technical Supervision on March 4, 1997 130
Implementation on September 1, 1997
This standard stipulates that the workpiece shall be accepted according to the acceptance limit. 4.1 Determination of acceptance limit method
GB/T3177-1997
Acceptance limit can be determined in one of the following two ways. a) The acceptance limit is determined by moving a safety margin (A) from the specified maximum material limit (MML) and minimum material limit (LML) into the workpiece tolerance zone, as shown in Figure 1. The value of A is determined as 1/10 of the workpiece tolerance (T), and its value is given in Table 1. LML
Upper acceptance limit
Lower acceptance limit
Acceptance limits for hole sizes:
Upper acceptance limit - minimum material limit (LML) - safety margin (A) Lower acceptance limit - maximum material limit (MML) + safety margin (A) Acceptance limits for shaft sizes:
Upper acceptance limit - maximum material limit (MML) - safety margin (A) Lower acceptance limit = minimum material limit (LML) + safety margin (A) 4
Upper acceptance limit
Lower acceptance limit
b) The acceptance limits are equal to the specified maximum material limit (MML) and minimum material limit (LML), that is, the A value is equal to zero. Table 1 Safety margin (A) and allowable value of measurement uncertainty of measuring instruments (u) um
Tolerance grade
Basic size
6 b. 60. 540. 91.4101. 0o. 91. 52. 3141.41. 32. 13. 2 25 2. 52. 33. 85. 6 404. 03. 66. d9. d60 6. d5. 49. d148 b. 80. 721. 21.8121.21.11. 82.7181.81. 62. 74. 130 3. 02. 74. 56.848 4. 84. 37. 21175 7. 56.81117151. 51. 42. 33. 4 22 2. 22. 03. 35. 0 36 3. 63. 35. 48. 1 58 5. 85. 28. 7 13|90 9. 08. 1 142090. 811. 42. d
11.01.72.5181.81.72.74.1272.72.44.16.1434.3.96.59.7707.06.311161 101110|172513.31.22.02.9212.11.93.24.7333.83.05.07.4525.24.77.812848.47 .613191313122029161.61.42.43.6252.52.33.85.393.93.55.98.8626.25.69.3141 0109.1523601614243619.91.72.94.3303.02.74.56.8464.64.16.910747.46.11171 2012111827190191729432.22.03.35.d353.53.25.37.9545.44.98.112878.77.8132 01401413213222d222033501252.52.33.85.640|4.Q3.66.09.0636.35.79.514/10q1 09.015231601615243625d25233856180
292.92.64.46.5464.6416.910727.26 .5111615121017261851817284229029264465323.22.94.87.2525.24.77.812818.17.3121813013|1219292102119324732032|29|4872315
400363.63.25.48.1575.75.18.413898.98.0 1320140141321322302321355236036325481315
400500404.03.6|6.09.0636.35.79.514979.78.71 522155161423352502523385640040366090131
Tolerance grade
Basic size
Greater than
GB/T3177-1997
Table 1(end)
100109.15140141321250|2523384004036606006054901000100901501400140135210120 1211|1818018162730030|274548048|43 7275075 6811012001201101801800180160270150 15 14 232202220 33 360 3632 54 580 58 52 8790090 8114015001501402302200220200330180|1816|2727027|24|41 430 43 3965|700706311011001101001701800180160270270027024940018
30210 2119 32 33033 30 50/52052 4778 840 84 76130130013012020021002101903203300330300490[250|25 23 38 390 39 3559|620/62|56 93/100010Q90/150160016014024025002502203803900390350 58050 | | tt | 53 54054 49 81 870 87 78 1301400140130210220022020d33035003503205305400540480 810400 40|36|60 63d 63|57 95 100d100 90 150160016015q24d2500250230380400040q360600630063057d 9401804
460 46 41 69 72072 6511011501510017018501801702802900290269440460046041069072007206501080180
250315
520 52 47 78 810 81 7312013001301 2019q2100210199320320032029048052005204707808100810730121d570 57 51 86 899 89 80139140014013021023002302193503600360320540570057051085089008908001330315
400 500 630 63 57 95 97d 97 87/1501500150140230250025d23038040004003606006300630570950970097d8701450Choice of acceptance limit method
The selection of acceptance limit method should be considered comprehensively in combination with the dimensional function requirements and their importance, dimensional tolerance grade, measurement uncertainty and process capability.
a ) For dimensions that comply with the tolerance requirements and dimensions with high tolerance grades, the acceptance limit shall be determined in accordance with 4.1a). b) When the process capability index C ≥ 1, the acceptance limit may be determined in accordance with 4.1b), but for dimensions that comply with the tolerance requirements, the acceptance limit may be determined in accordance with 4.1b). For the required dimensions, the acceptance limit on the side of the maximum physical limit shall still be determined in accordance with 4.1a). c) For dimensions with skewed distribution, the acceptance limit may be determined only on the side of the dimension in which it is skewed in accordance with 4.1a). d) For dimensions that are not compatible and have general tolerances, the acceptance limits are determined in accordance with 4.1b). 5 Selection of measuring instruments
5.1 Principles for the selection of measuring instruments
According to the measurement uncertainty caused by the measuring instrument The measurement uncertainty of the measuring instrument should be equal to or less than the selected u1 value. The allowable value of measurement uncertainty (u1) is divided into three grades according to the ratio of measurement uncertainty (u) to workpiece tolerance: IT6~IT11 is divided into three grades: I, II, and sub; IT12~IT18 is divided into I, I The three values of measurement uncertainty (u) are 1/10, 1/6, and 1/4 of the workpiece tolerance respectively. The allowable value of measurement uncertainty (ul) of the measuring instrument is approximately The measurement uncertainty (u) is 0.9 times, and its three-level values are listed in Table 1.
5.2 Selection of the allowable value of measurement uncertainty (ui) of the measuring instrument Select the allowable value of measurement uncertainty (u) of the measuring instrument in Table 1. In general, grade I is preferred, followed by grade II
6 Arbitration
Disputes over measurement results may be resolved by using more accurate measuring instruments or by methods agreed upon by both parties in advance. 132
GB/T3177-1997
Appendix A
(Standard Appendix)
Confidence Probability of Measurement Uncertainty
The evaluation of measurement uncertainty in the standard shall comply with the provisions of the relevant standards. The confidence probability is 95%. Appendix B
(Suggested Appendix)
Evaluation of the probability of misjudgment and acceptance quality
According to the acceptance principle: the acceptance method used should only accept Workpiece within the limit. However, since there are errors in both measuring instruments and measurement systems, any measurement method may have a certain probability of misjudgment. This appendix explains the calculation of the probability of misjudgment caused by measurement errors, and uses the magnitude of the probability of misjudgment to evaluate the quality of acceptance. B1 Calculation of the probability of misjudgment
B1.1 Basic concepts
There are two types of misjudgment when accepting workpieces: misjudgment and misjudgment. Misjudgment refers to the failure of a workpiece to be accepted due to a size exceeding the specified size limit. The workpieces that are within the specified size limit are judged as qualified; the wrong rejection refers to the workpieces that are within the specified size limit being judged as scrap. The wrong acceptance affects the product quality, and the wrong rejection causes economic losses. The probability of wrong acceptance (hereinafter referred to as the wrong acceptance rate) or the probability of wrong rejection (hereinafter referred to as the error rejection rate) is collectively referred to as the probability of misjudgment. B1.2 Calculation formula
B1.2.1 Code
See Table B1.
False acceptance rate
False rejection rate
Workpiece size
Measurement error
Workpiece size density functionbzxZ.net
Measurement error density bacteria count| |tt||Standard deviation of workpiece size distribution
B1.2.2 Formula
See Figure B1.
g(y)dy
, the second term
(the first term on the right side of the equal sign
measurement error distribution standard deviation
workpiece tolerance|| tt||Safety margin
Measurement uncertainty
Process capability index
Measurement error ratio
g(y)dy
g(y) dy
GB/T 3177
When f() is a symmetric distribution function, the above two equations can be simplified to: T
g(y)dy
B1 .3 Conditions that determine the probability of misjudgment
[dyin=2
g(y）
g(y)dy
g(y)dy
Figure B1 Workpiece size and measurement error
It can be seen from the calculation formula that m and n are determined by the distribution form of y and its integral limit. Here, the workpiece tolerance T is in units of standard deviation α, and the measurement uncertainty u is in units of standard deviation s. Introducing the process capability index C,=T/Cc, the measurement error ratio=2u/T, so the error rate m and the scrap rate n are determined by: f(z).Cpvg(y) and A. Among them, f(r) and C, are determined by the process conditions, g(y) and are determined by the measurement conditions, and A determines the acceptance limit.
B2 Acceptance limit determined according to 4.1b) Probability of misjudgment when accepting workpieces B2.1 Workpiece size follows normal distribution
Acceptance limit is determined according to 4.1b) of the standard, that is, A=0. Workpiece size follows normal distribution, Cp=7/6; measurement error follows normal distribution and u=2s. At this time, the values of m and n are shown in Figure B2 and Table B2. 13.1
GB/T 3177—1997
Normal distribution
um1/10
Normal distribution error rate m and error rejection rate n
Normal distribution
As can be seen from Figure B2 or Table B2, both workpiece size and measurement follow normal distribution, and usually the values of m and n are not large. For example, when C,=0.67, m is about 1%, and n is about 2%; when C,=1, m is about 0.08%, and n is about 0.4%. When the workpiece size follows a normal distribution and the measurement error follows a uniform distribution, u=1.73s, then both m and n increase by about 10%, B2.2 Workpiece size follows a skewed distribution
B2.2.1 Skewed distribution
Under single-piece production conditions, workpiece size may tend to a skewed distribution. This appendix uses the β distribution to describe the skewed distribution, and its equation is: f(α) B(pQ)
p-1(1 - )9-1
Let p=1.5, Q=3, or vice versa p=3, 9=1.5, and we get two skewed distributions with different inclinations, as shown in Figure B3. At this time: f(x) = 6.5625z0.5(1 - α)2 or f(）) = 6.56252(1—)0.5
The mathematical expectation E(z), standard deviation α, relative asymmetry coefficient e, and relative distribution coefficient K of the distribution are: E(r) = 0.33
or E(r) 0.67
(b - α) pg
(p+q)p+q+i
p+ap+e+i
Here, α=0, b=1. The skewed distribution and its parameters are shown in Figure B4. 13.5
Figure B3 Skewed distribution
B2.2.2 Probability of misjudgment
GB/T3177—1997
Figure B4 Skewed distribution and its parameters
Acceptance limit is determined according to Article 4.1b) of the standard, that is, A=0. The workpiece size follows the skewed distribution, C,=T/5a, and the measurement error follows the normal distribution and u=2s. At this time, the values of m and n are shown in Figure B5 and Table B3. n.%
Skewed distribution
Skewed distribution
Miss acceptance rate m and scrap rate n in skewed distribution
It can be seen from Figure B5 or Table B3 that when the workpiece size follows the skewed distribution, the values of m and n are more than doubled compared with the normal distribution. For example, when C,=0.67, m is about 2%, n is about 4%, and when C,=1, m=0, n is about 3%. When the workpiece size follows a skewed distribution and the measurement error follows a uniform distribution, u=1.73s, then the values of m and n both increase by about 10%. B2.3 The workpiece size follows a uniform distribution
The acceptance limit is determined according to Article 4.1b) of the standard, i.e. A-0. The workpiece size follows a uniform distribution, C,T/3.46g; the measurement error follows a normal distribution and u=2s is taken. At this time, the values of m and n are shown in Figure B6 and Table B4. 186
GB/T 3177-1997
Uniform distribution
Uniform distribution
Figure B6 The acceptance rate m and the rejection rate n when the workpiece size follows a uniform distributionTable B4
It can be seen from Figure B6 or Table B4 that when the workpiece size follows a uniform distribution, the values of m and n both increase by 1 to 2 times compared with the normal distribution. For example, when C,=0.67, the values of m and n are both 4%; when C,=1, m=0, n=6%. When the workpiece size follows uniform distribution and the measurement error also follows uniform distribution, u=1.73s, then the values of m and n both increase by about 30%. B3 According to Article 4.1a), the probability of misjudgment when accepting the workpiece with acceptance limit is determined. Let A=0.1/5-2, 2/5·u, 3/5·u, 4/5·w, 5/5w, and get different acceptance limits. In this chapter, when C=0.67 is taken, the probability of misjudgment when accepting the workpiece with different acceptance limits under different distribution conditions of workpiece size. It can be seen from Figures B7, B8, and B9 that as the A value increases, the m value decreases rapidly and the n value increases sharply. In order to reduce the m value to a very small value and the n value not to be too large, this standard adopts multiple acceptance limits; when C,=1, A=0 is taken for each level of I, I, and III, that is, no shrinkage, and the limit size of the workpiece is used as the acceptance limit. When C,1, A=5/5·u for Grade I, i.e. 100% indentation; A=3/5·u for Grade II, i.e. 60% indentation; and A=2/5·u for Grade II, i.e. 40% indentation, and the acceptance limits are determined accordingly. B3.1 Workpiece dimensions follow normal distribution
When the workpiece dimensions follow normal distribution, the values of m and n obtained from different acceptance limits are shown in Figure B7 and Table B5. It can be seen from Figure B7 or Table B5 that when A=1 u, the value of the error rate m is zero, but the value of the error rate n is too large, even as high as 30%. The values of m and n for each acceptance limit specified in this standard are shown in Table B6. It should be noted that A=0 is allowed only when the matching size is C,≥1. Therefore, the value of the first item of m or n in Table B6 is taken from the corresponding value when C,1 in Table B2. 137
Normal distribution
Cp= 0. 67
0=1/10
GB/T3177-1997
5/5A/u
Normal distribution
Figure B7 Variation of m and n values with A value in normal distributionTable B5
B3.2 Workpiece size follows skewed distribution
5/5A/u
When the workpiece size follows skewed distribution, the m and n values obtained by different acceptance limits are shown in Figure B8 and Table B7. It can be seen from Figure B8 or Table B7 that each m and n value is larger than the corresponding value in normal distribution. The m and n values of the acceptance limits specified in this standard are shown in Table B8. The value of the first item of m or n in Table B8 is taken from the corresponding value of C,1 in Table B3. m.%
Skewed distribution
0=1/10
5/5A/u
Skewed distribution
Figure B8 Variation of m and n values with A value in skewed distribution2/5
5/5A/u
GB/T3177—1997
B3.3Workpiece size follows uniform distribution
When the workpiece size follows uniform distribution, the m and n values obtained by different acceptance limits are shown in Figure B9 and Table B9. It can be seen from Figure B9 or Table B9 that each m and n value is larger than the corresponding value in normal distribution. The m and n values of the acceptance limits specified in this standard are shown in Table B10. The value of the first item of m or n in Table B10 is taken from the corresponding value when Cp=1 in Table B4. Batch, %
Uniform distribution
C, 0. 67
—1/10
Uniform distribution
Cp= 0. 67
v=1/101
Figure B9 Variation of m and n values with A value in uniform distribution Table B9
Table B10
n, %1
5/5A/k
C1Basic concept
GB/T 31771997
(Appendix of prompt)
Error rate caused by workpiece shape error
General measuring instruments measure workpieces according to the two-point measurement method, and the measured value is the actual local size. Due to the shape error of the workpiece, the local size of a certain place is qualified, and the effective size or the local size of another place may exceed the specified size limit. The two-point measurement method violates Taylor's principle and has a certain error rate. Usually, the shape error is controlled within the dimensional tolerance band by the process. However, some shape errors cannot be measured by the two-point measurement method, and the measurement position that is most conducive to revealing the shape error is not easy to determine. This appendix assumes that the process only measures the middle size of the workpiece (least square cylinder diameter), and the middle size and shape error are combined as two independent random variables during acceptance. C2 calculation formula
C2.1 code
See Table C1.
C2.2 Formula
Error rate caused by shape error
Workpiece size
Dimension increment caused by shape tolerance
Shape error
Workpiece size density function
Dimension increment density function
Shape error density function
Error rate of workpieces whose error effect size exceeds the maximum physical size: 4)
f(r）
A) r(1-C)f+
h(z)dady
(1-C)f Jo
C3According to 4.1b), the acceptance limit is determined. The error rate when accepting the workpiece is dimensional tolerance
Shape tolerance
Safety margin
Process capability index
Shape error ratio
Shape error value
Introduce the process capability index C, a T/6a, and the shape error ratio r=T:/T. Assume that the workpiece size follows the normal distribution, the size increment follows the inverse sine distribution (determined by the shape error type), and the shape error follows the skewed distribution. The error rate of the workpiece whose error effect size exceeds the maximum physical size is shown in Figure C1. Among them, a) is the shape error that can be measured by the two-point measurement method (such as convex, concave, even-numbered prisms, etc.), and b) is the shape error that cannot be measured by the two-point measurement method (such as odd-numbered prisms, axis bending, etc.). i
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