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GB/T 39741.1-2021: Plain bearings - Tolerances - Part 1: Fits
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Plain bearings - Tolerances - Part 1: Fits
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GB/T 39741.1-2021
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Basic data | Standard ID | GB/T 39741.1-2021 (GB/T39741.1-2021) | | Description (Translated English) | Plain bearings - Tolerances - Part 1: Fits | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | J12 | | Word Count Estimation | 14,121 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 39741.1-2021: Plain bearings - Tolerances - Part 1: Fits---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Plain bearings - Tolerances - Part 1.Fits
ICS 21.100.10
J12
National Standards of People's Republic of China
Sliding Bearing Tolerance Part 1.Fit
(ISO 12129-1.2019, IDT)
Released on 2021-03-09
2021-10-01 implementation
State Administration of Market Supervision and Administration
Issued by the National Standardization Management Committee
Foreword
GB/T 39741 "Tolerance of Sliding Bearings" consists of the following two parts.
---Part 1.Cooperation;
---Part 2.Geometric tolerances and surface roughness of shaft and thrust shoulder.
This part is Part 1 of GB/T 39741.
This section was drafted in accordance with the rules given in GB/T 1.1-2009.
The translation method used in this section is equivalent to ISO 12129-1.2019 "Tolerance of Sliding Bearings Part 1.Fitting".
This part was proposed by China Machinery Industry Federation.
This part is under the jurisdiction of the National Sliding Bearing Standardization Technical Committee (SAC/TC236).
Drafting organizations of this section. China Machinery Productivity Promotion Center, Hunan Chongde Technology Co., Ltd., Shenke Sliding Bearing Co., Ltd.,
Zhejiang Zhuji Bearing Factory Co., Ltd., Zhejiang Zhongda Precision Components Co., Ltd., Zhejiang Changsheng Sliding Bearing Co., Ltd., Zhejiang
Jiang Shuangfei Oilless Bearing Co., Ltd., Jiashan Sanfu Sliding Bearing Co., Ltd., Jiaxing Meiteer Baoxin Machinery Industry Co., Ltd.
This part is explained by the National Technical Committee for Standardization of Sliding Bearings.
Introduction
Since the standard deviations specified by ISO 286-1 and ISO 286-2 cannot be used to establish a bearing clearance fit, the design of sliding bearings requires
The clearance fit corresponding to the average relative clearance of all bearings within the nominal size range (with approximately equal), so this document is formulated.
Sliding Bearing Tolerance Part 1.Fit
1 Scope
This part of GB/T 39741 specifies metal sliding shafts with an average relative bearing clearance ψm of 0.56‰~3.15‰ in general machinery
The supporting matching system and other gap ranges can be selected according to the technical requirements of specific applications.
This matching system is not suitable for thin-walled bushings and thin-walled bushings, because thin-walled bushings and thin-walled bushings are unique, and they mainly measure wall thickness
Rather than the diameter, and the size will vary with assembly.
This part does not apply to non-circular bearings or tilting pad bearings, nor does it apply to extreme clearance (large or very small) conditions.
Special tolerance requirements determined after performance.
This section is mainly applicable to rotating mechanical parts and spindles, but also to similar applications.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
Terms and definitions are not given in this document.
The website of the ISO and IEC standardized terminology database is as follows.
4 Cooperating system
The matching system specified in this section is the basic hole system, and the basic deviation H of the bearing hole diameter is in accordance with ISO 286-2.The tolerance zone of the journal and
The corresponding bearing average relative clearance ψm is related.
5 Average relative clearance of bearings
The average relative clearance ψm (unit. one thousandth, ‰) of the bearing in a certain nominal size range is given by equations (1) and (2).
ψm=
CD,m
Dm
(1)
Where.
CD,m---the average value of the absolute diameter clearance of the bearing, in micrometers (μm).
CD,m=
CD,max-CD,min
(2)
Where.
CD,max---the maximum value of the absolute diameter clearance of the bearing;
CD, min---the minimum value of the absolute diameter clearance of the bearing;
Dm --- the arithmetic average of the nominal size, in millimeters (mm).
Example.
The nominal size range is 250mm~280mm, then the arithmetic average of the nominal size is.
Dm =
2 mm=265mm
For ψm=1.6‰, the average bearing diameter clearance is calculated by Table 1 and formula (2).
CD,m =
0.466 0.382
2 mm=0.424mm
So as to get the average relative clearance of the bearing.
ψm =
CD,m
Dm =
0.424
265 =1.6‰
6 Tolerance zone
6.1 Tolerance
Tolerances are selected according to the following principles. For the same bearing average relative clearance ψm, all between the minimum and maximum nominal size
In this case, the maximum deviation of the relative clearance of all bearings within the tolerance zone is within the range. The smaller limit deviation depends on the economy
Sex and processing methods.
In each fit, the tolerance zone of the journal is smaller than the tolerance zone of the corresponding bearing hole by 1 IT (the basic tolerance specified in ISO 286-1, etc.
level).
6.2 Basic deviation
The basic deviation is determined by the average relative clearance ψm of the bearing.
6.3 Average relative clearance value of bearing
Each of the following values of ψm corresponds to a tolerance zone, and the unit is ‰.
---0.56;
---0.8;
---1.12;
---1.32;
---1.6;
---1.9;
---2.24;
---3.15.
6.4 Symbols
The symbol for the average relative clearance of the bearing is ψm. In the case where the Greek letter is not available, C* can be used to replace the Greek letter ψ.
7 Nominal size range
The nominal size range is more densely divided than ISO 286-2, and the maximum deviation under the average relative clearance of the bearing is closer.
8 Limit deviation
The limit deviation of the journal is shown in Table 1.
9 Maximum clearance and minimum clearance
The minimum clearance and maximum clearance between the journal and the bearing hole required for the bearing design calculation and the limit deviation of the journal are shown in Table 1.
The tolerance zone corresponding to the relative clearance of the bearing is shown in Table 2.
10 Example
The average relative clearance of the bearing ψm=1.12‰, and the expression form of the matching size of the journal of.200mm is as follows.
Preferred form.
ϕ200ψ1.12
Optional form (when Greek letters are not available).
ϕ200C*1.12
Optional form (when the subscript is not available).
ϕ200(C*1.12)
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