GB/T 39741.1-2021Plain bearings - Tolerances - Part 1: Fits (English PDF)

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 psim of 0.56 per mille~3.15 per mille 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 psim is related.

5 Average relative clearance of bearings

The average relative clearance psim (unit. one thousandth, per mille) of the bearing in a certain nominal size range is given by equations (1) and (2).

psim=

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 psim=1.6 per mille, 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.

psim =

CD,m

Dm =

0.424

265 =1.6 per mille

6 Tolerance zone

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 psim=1.12 per mille, and the expression form of the matching size of the journal of.200mm is as follows.

Preferred form.

dia. 200psi1.12

Optional form (when Greek letters are not available).

dia. 200C*1.12

Optional form (when the subscript is not available).

dia. 200(C*1.12)