GB/T 39641-2020Methods for gaging fastening screw threads by thread indicating gages (English PDF)

1 Scope

This standard specifies the method for the thread indicator gauge to detect the tightening thread parameters: Fastening thread parameters include: active pitch diameter, basic thread bottom

Diameter, design bottom diameter, pitch diameter, single pitch diameter, radial pitch difference, axial pitch difference, pitch (lead), flank angle, tooth profile comprehensive deviation, top diameter

Relative pitch diameter jump:

This standard applies to the detection of fastening thread parameters (the minimum nominal diameters of internal and external threads are 4:8mm and 1mm, respectively):

2 Normative references

The following documents are indispensable for the application of this document: For dated reference documents, only the dated version applies to this article

Pieces: For undated references, the latest version (including all amendments) applies to this document:

GB/T 14791 Thread Terminology

JJF1001 General measurement terms and definitions

JJF1059:1 Evaluation and expression of measurement uncertainty

3 Terms and definitions

The following terms and definitions defined in GB/T 14791, JJF1001 and JJF1059:1 apply to this document:

3:1

Thread detection testonscrewthreads

A set of operations to determine whether a threaded product meets the requirements of the corresponding standard:

Note: These operations usually include the measurement of the thread parameter value and (or) whether it exceeds the allowable limit:

3:2

Variationofpitchdiameterindifferentradialdirections

Within a lead length, the maximum difference between each radial pitch diameter (take a positive value):

Note: The radial cross-sectional shape of the medium diameter cylinder is usually elliptical or triangular: Two-point contact (two probes separated by 180°) and three-point contact (three probes)

The head spacing is 120°) gauge to measure the pitch diameter in the elliptical and triangular cross-sections:

[GB/T 37050-2019, definition 3:2]

3:3

Variationofpitchdiameteratdifferentaxialpositions

The maximum difference (positive value) between the pitch diameters of each axial position in the thread axis plane and the specified screwing length:

Note: In the case where the supplier and the buyer agree, the axial pitch diameter difference can only be measured at both ends of the complete thread:

[GB/T 37050-2019, definition 3:3]

3:4

Cumulative form deviation

Within the specified screwing length, the deviation from other thread parameters (pitch, flank angle, radial pitch diameter difference, axial pitch diameter difference, etc:) other than pitch diameter

The maximum change in the diameter of the action caused by the combined action: