Some standard content:
JB/T9184—1999
This standard is a revision of JB/Z304--87 "Statistical Dimension Tolerance". During the revision, the original standard was edited, and the main technical content remained unchanged.
This standard replaces JB/Z304-87 from the date of implementation. Appendix A and Appendix B of this standard are both informative appendices. This standard is proposed and managed by the National Technical Committee for Standardization of Tolerances and Fits. The drafting units of this standard are: Mechanical Science Research Institute, Huazhong University of Science and Technology. The main drafters of this standard are: Li Xiaopei, Cheng Deyun. 243
1 Scope
Mechanical Industry Standard of the People's Republic of China
Statistical dimension tolerances
Statistical dimension tolerancesJB/T9184-1999
Replaces JB/Z.304-87
This standard specifies the definition of terms for statistical dimension tolerances, the scheme of probability distribution characteristics of actual dimensions and the marking of statistical dimension tolerances on drawings.
This standard applies to length dimensions, especially to fitting dimensions and dimensions with higher precision. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1800.1-1997 Limits and fits Part 1: Vocabulary GB/T1800.2-1998 Limits and fits Part 2: Basic provisions for tolerances, deviations and fits GB/T1800.3-1998 Limits and fits Part 3: Tables of standard tolerances and basic deviations GB/T5847-86 Calculation method of dimension chain 3 Definitions This standard adopts the following definitions (refer to Figure 1). Lmin 3.1 Statistical dimensional tolerance Tp Dimensional tolerance that specifies the probability distribution characteristics of the actual size. 3.2 Statistical dimensional tolerance of holes TH
Approved by the State Bureau of Machinery Industry on June 28, 1999 244
Implemented on January 1, 2000
JB/T 9184-1999
Hole tolerance that specifies the probability distribution characteristics of actual dimensions. 3.3 Statistical dimensional tolerance of shafts Tps
Shaft tolerance that specifies the probability distribution characteristics of actual dimensions. 3.4 Statistical minimum clearance (or interference) Zpmin Minimum value of the allowable clearance (or interference) associated with a certain confidence level 3.5 Statistical maximum clearance (or interference) Zpmx Maximum value of the allowable clearance (or interference) associated with a certain confidence level. 3.6 Statistical fit tolerance TF
The fit tolerance that specifies the probability distribution characteristics of the actual clearance (or interference), which depends on the probability distribution characteristics of the actual dimensions of the holes and shafts that fit each other and the permissible distribution range, and is related to a certain confidence level. 3.7 Statistical dimensional tolerance of component rings Tp
The tolerance of component rings that specifies the probability distribution characteristics of the actual dimensions. 3.8 Statistical dimensional tolerance of closed rings Tos
The tolerance of closed rings that specifies the probability distribution characteristics of the actual dimensions, which depends on the probability distribution characteristics of the actual dimensions of the component rings and the permissible distribution range, and is related to a certain confidence level. 3.9 Intermediate dimension Lc
The arithmetic mean of the maximum limit dimension Imax and the minimum limit dimension Lmin. 3.10 Upper edge zone
The part of the dimensional tolerance zone with the maximum limit dimension Lmax as the upper limit. 3.11 Upper edge zone width Wu
The part of the dimensional tolerance occupied by the upper edge zone. 3.12 Lower zone
Part of the dimensional tolerance zone with the minimum limit size Lmin as the lower limit. 3.13 Lower zone width W
Part of the dimensional tolerance occupied by the lower zone. 3.14 Middle zone
Part of the dimensional tolerance zone located between the upper zone and the lower zone. 3.15 Middle zone width Wc
, Part of the dimensional tolerance occupied by the middle zone. 3.16 Middle zone upper limit (upper zone lower limit) Lcmax The boundary dimension between the middle zone and the upper zone.
3.17 Middle zone lower limit (lower zone upper limit) Lcmin The boundary dimension between the middle zone and the lower zone.
3.18 Upper zone frequency Pumax
The maximum frequency at which the actual size of the part is allowed to fall within the upper zone. 3.19 Lower zone frequency Pl.max
The maximum frequency at which the actual size of the part is allowed to fall within the lower zone. 3.20 Frequency of the middle zone Pcmin
The minimum frequency of the actual size of the part falling within the middle zone. 3.21 Arithmetic mean interval B-
The interval that limits the arithmetic mean of the actual size. 3.22 Median interval Bz
The interval that limits the median of the actual size.
3.23 Upper limit of standard deviation max
The maximum value of the standard deviation of the actual size allowed. Schemes for specifying the probability distribution characteristics of the actual size JB/T 9184—1999
One of the following three schemes can be used to specify the probability distribution characteristics of the actual size: a) Specify the upper limit Lcnax, lower limit Lcnin and middle zone frequency Pcmin of the actual size, or specify the upper limit Lmax, lower limit Lcmax and upper zone frequency Pumax of the actual size, and the upper limit Lacmin, lower limit Lmin and lower zone frequency PLmax of the lower zone; b) Specify the arithmetic mean interval B of the actual size; c) Specify the median interval B of the actual size. In some cases, when b) or c) is adopted, the upper limit of the standard deviation of the actual size αmax should also be specified. 5 Statistical dimension tolerance marking on the drawing
5.1 Marking according to (Chapter 4) a) scheme
For example: 55±0.06±0.03P86%
Where: 55mm is the basic size, (55±0.06)mm is the maximum limit size, and 550.06)mm is the minimum limit size. P86% means that Pcmim is equal to 86%, that is, at least 86% of the parts are included in the middle area (55±0.03)mm. If there is no special explanation, then:
1Pemm ×100%=7%
Pumax -PLmux =
That is, at most 7% of the parts are included in the upper area 55+8:8gmm or the lower area 552.%.%mm. 5.2 Marking according to (Chapter 4) b) scheme
For example: 55±0.06±0.02X
indicates that the arithmetic mean of the actual size must be within the range of (55±0.02) mm. If αmax needs to be specified, it can be added in brackets: 55±0.06±0.02X(omx0.02)
5.3 Marking according to (Chapter 4) c) scheme
For example: 55±0.06±0.02x
indicates that the median of the actual size must be within the range of (55±0.02) mm. If αmx needs to be specified, it can be added in brackets: 55±0.06±0.02X(omax<0.02)
5.4 Simplified marking
Statistical dimension tolerances can be simplified according to the method shown in Figure 2. When simplified notation is used, the specific requirements for statistical dimensional tolerances shall be specified in the technical conditions or uniformly specified in the technical documents.
JB/T 9184—1999
A1 Introduction
JB/T 9184
Appendix A
(Suggestive Appendix)
Application of statistical dimensional tolerances in hole and shaft fit The probability distribution of the actual size of holes and shafts has a great influence on the fit performance. The use of statistical dimensional tolerances for holes and shafts can enable the product to achieve better technical and economic effects. For example:
a) The certainty of transition fit can be guaranteed;
b) The fit with the best "clearance or interference" can be obtained more often; c) The probability of the limit size of the hole and shaft meeting during assembly can be reduced; d) The wear reserve and strength reserve of parts can be improved; e) The error rate and scrap rate in measurement can be reduced: f) When the fit tolerance requirement is small and it is difficult to achieve in the process, the hole and shaft tolerance level can be appropriately reduced. A2 Probability distribution of "occasional interference"
A2.1 General method for determining the probability distribution function of "clearance or interference" X represents the actual size of the hole and Y represents the actual size of the shaft. If the two are independent random variables, then "clearance or interference" Z-X-Y is also a random variable.
If the probability density function of X is f(r), and the probability density function of Y is y(y), then the distribution function of Z is: F(z)=
The probability density function of Z is:
f(r)fa(y)drdy..
f(z)=F(z)
f,(y)f(y+a)dy
A2.2 General method for determining the statistical limit "clearance or interference" and the statistical fit tolerance The statistical limit "clearance or interference" is related to a certain confidence level 1-α. A2.2.1 Two-sided requirements
a) For a symmetrical distribution
, Zpmin can be obtained.
Zpmax can be obtained
Statistical fit tolerance T'pF is obtained by the following formula: b) For asymmetric distribution
Let ααα
F(Zpmin)=
F(Zpmax)=
TpF=IZrmx
F(Zpmin）
·（A3）
Zpmin can be obtained
Zrinax can be obtained
JB/T9184--1999
F(Zpmax)=
The calculation of statistical fit tolerance T is the same as formula (A6). A2.2.2 One-sided requirement
Zpmin can be obtained.
Zpmmx
Statistical fit tolerance Tpr can be obtained by the following formula:
Where: Zmax, Zmmn are the limit "clearance or interference". F(Zrmin）α
F(Zpmax ）
I'pF -- [Zmax-Zpmin !
T'pr = [Zprmax Znin
中+中
A2.2.3 When the actual size of the hole and shaft is normally distributed (T:Wc=2:1,Pcmin-86%), the statistical limit of the commonly used fit "clearance or interference" is preferred as shown in Table A1.
A3 Provisions on the requirements for the probability distribution characteristics of the actual size of the hole and shaft A3.1 Division of tolerance zones
a) For symmetrical distribution, it is recommended:
T:Wc=2+1
b) For asymmetrical distribution, the division of the three intervals can be determined according to actual conditions. A3.2 Determination of frequency
A3.2.1 Actual size is symmetrically distributed
·(A13)
a) When it is close to normal distribution, if the tolerance zone is divided according to T:Wc=2:1, Pcmin=86% is recommended. At this time, the maximum frequency allowed in the upper and lower edge areas is!-Pecnin -
b) When it is similar to the Simpson (triangular) distribution, if the tolerance zone is divided according to T: Wc-2: 1, it is recommended that Pcmin = 75%, and the maximum frequency allowed in the upper and lower areas is! # = 12.5%;
c) When it is similar to the uniform distribution, if the tolerance zone is divided according to T: Wc = 2: 1, it is recommended that Pcmin = 50%, and the maximum rate allowed in the upper and lower areas is Pe = 25%.
A3.2.2 The actual size is distributed asymmetrically
Generally, the upper area frequency Pumax and the lower area frequency Plmx should be specified at the same time. A3.2.3 According to the design requirements, when only the frequency requirements of a certain area are considered, only the upper area frequency Pumx or the lower area frequency Plmx can be specified. Frequency PLmax of the side zone
A3.3 Marking examples
a) For symmetrical distribution, such as: 455±0.06±0.03P86%, indicating that the frequency of the upper and lower side zones cannot exceed 7%; b) For asymmetrical distribution, such as 55±0.06±0:P9%29%P5%, indicating that the frequency of the upper side zone cannot exceed 9%, and the frequency of the lower side zone cannot exceed 5%;
c) Only specifying the frequency of a certain side zone, such as $55±0.069:%P7%, indicating that there is a frequency requirement only for the lower side zone, and it cannot exceed 7%. 249
A4 Simplified calculation of statistical fit tolerance
A4.1 If T:Wl—2:1,Pcmin=86%
JB/T 9184
4++++44
Where: TH is the hole tolerance, T. is the shaft tolerance, and the coefficient K. can be found in the relevant probability and mathematical statistics manual. If T=Ts, and 1-α=99.73%(K.3)
TPF=0.71Tv
If Th=1.6Ts (the hole is lower than the shaft), and 1-α=99.73%(K. =3), TpF - 0.73T,
A4.2 If T+Wc=2:1.Pcmin—75%
If Th=Ts, and 1α=99.73%
TPF=TR
A4.3 If T:Wc=2:1,Pcmin=50%
If Th=Ts, and 1—α=99.73%
A5 Application example
TpF 0. 79TF
TpF=TF
TpF—0.95Tp
Example 1 According to the use requirements, the fit of a machine tool component is selected as Φ40250
·(A14)
（A16)
：（A17)
（A18)
（A22)
, but it should be avoided that the hole and shaft with zero actual deviation are assembled together. In this case, statistical dimensional tolerance can be used.
If it is stipulated that: hole $40+039
+8.03P86%
shaft 40--.025
0.016P86%
it can be found from Table A1:
statistical minimum clearance Zrmin一+9um
JB/T 9184--1999
statistical maximum clearance Zpmax=+55μm
It can be seen that the unfavorable situation of zero clearance will basically not occur when the hole and shaft are assembled. In order to highlight the restriction on the frequency of small gaps, the frequency of a certain side area can also be specified: hole 40+8 039+90P7%
shaft $40-.02s -0. cs P7%
Example 2 The fit of a certain component is selected as *60H8.
, and the gap is +0.01~-
+0.086mm, but according to the design requirements, the performance is best when the gap is between +0.029~g7
+0.067mm. At this time, statistical dimensional tolerance can be used. If it is specified: hole 60+0.046￥8.811P86%8-8:842 P86%
shaft±60=0.010
According to this regulation, 86% of the holes and shafts will be in the best gap state after assembly. Example 3 The basic size of the rocker hole and shaft in a sensor is 2.5 μm. According to the product performance requirements, the gap after assembly should be within +2.5~- +-7.5 μm
If you choose: hole 42.5*0.004
shaft $2.5-0.002
, the maximum gap is Zmax=+7μm
and the minimum gap is Zmin=+2μm
, which can meet the requirements. However, the tolerance grade of the hole is IT4, and the tolerance grade of the shaft is IT3. The processing accuracy is high, which is difficult to achieve in terms of technology. In addition, it is inconvenient to assemble in groups because it is a small batch production. At this time, statistical dimensional tolerance can be used. If it is specified: hole $2.5+8.002+8.085P86% shaft $2.5±0.002±0.001P86%
, take 1-α95% and find K. =1.96, from formula (A14), formula (A21) and formula (A22), we can get: statistical maximum clearance Zpmax = + 7. 3um
statistical minimum clearance Zrmin = + 2.7μm
That is, more than 95% of the parts can meet the requirements, and the tolerance grade of the hole is reduced to IT6, and the tolerance grade of the shaft is reduced to IT5. Obviously, it is easier to achieve in terms of technology.
Basic hole system
Basic shaft system
JB/T 9184-- 1999
Table A1 gives priority to the statistical limits of commonly used fits "clearance or interference\(T:W:=2:1,Pcmin-86%) H6/f5
Basic size
>3～6
>6～10
≥10～14
≥14～ 18
>18～24
>24～30
>30～40
>40～50
>50～65||tt| |≥65 ~80
≥80～100
>100～120
≥120～140
≥140～160
>160～180||tt ||>180～200
>200～225
>225～250
>250～280
>280～315
>315～ 355
>355~400
≥400~450
>450~500
1H6/g5
H8/e7 |H8/f7- H8 /g7 |H8/h7- H8/d8H7/f6
H7/g6H7/h6
1F7/h6
G7/h6|H7/h6E8/h7F8/h7
“+” value in the table is the clearance amount, and the value is the interference amount. The fit marked in 2 is the preferred fit.
H8/h7D8/h8
Basic hole system
Basic shaft system
Basic size
>3～6
≥6～10
>10～14| |tt||≥14~18
>18~24
>24～30
≥3040
≥40～50
>50～ 65
>65～80
>80～100
>100～120
>120～140
≥>140～160||tt ||>160～180
>180--200
>200～22 5
>225250
>250～280
>280～315
>315～355
≥355～400
> 400～450
>450～500
JB/T9184—1999
Table A1 (continued)
H8/h8H9/c9H9/d9H9/e9||tt| |D9/h9-
+138+33 8
H9/f9H9/h9H10/e10|H10/d10|H10/h10F9/h9
D10/h10|H10/h10
Basic hole system
Basic shaft System
Basic size
>3～6
>6～10
>10～~14
JB/T9184-1999||tt| |Table A1 (continued)
H11/a11|H11/b11 HI1/c11 |H1[/d11|H/1/h11 -/H12/b12|H12/h12| H6/js5[A11/h11|B11/h11/c11/h117D11/hn1|H11/h11B12/h12H12/h12+372
>14~18
>18~24
>24～30
>30-~40
>40～50
>50～65
>65～80
>80～100
>100～120
>120～ 140
≥140~160
>160~180
>180~200
>200~225
225~250l
250~280
280~315
>315~355
>355~400
>400~450
>450~500||tt ||1+1767
14-117
++ 597
11916-+184
JS6/h5
[K6/h3||tt ||— 20H6/js5[A11/h11|B11/h11/c11/h117D11/hn1|H11/h11B12/h12H12/h12+372
>14~18
>18~24
>24～30
>30-~40
>40～50
>50～65
>65～80
>80～100
>100～120
>120～ 140
≥140~160
>160~180
>180~200
>200~225
225~250l
250~280
280~315
>315~355
>355~400
>400~450
>450~500||tt ||1+1767
14-117
++ 597
11916-+184
JS6/h5
[K6/h3||tt ||— 20H6/js5[A11/h11|B11/h11/c11/h117D11/hn1|H11/h11B12/h12H12/h12+372
>14~18
>18~24
>24～30
>30-~40
>40～50
>50～65
>65～80
>80～100
>100～120
>120～ 140
≥140~160
>160~180
>180~200
>200~225
225~250l
250~280
280~315
>315~355
>355~400
>400~450bzxZ.net
>450~500||tt ||1+1767
14-117
++ 597
11916-+184
JS6/h5
[K6/h3||tt ||— 20
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