1 Scope
This document specifies the type and dimensions, requirements, test conditions and methods, marking and packaging of metric series measuring needles for measuring threads.
This document applies to the metric series of measuring needles (hereinafter referred to as "measuring needles") for measuring the middle diameter of common threads (M), uniform threads (UN), 55° pipe threads (G,R) and trapezoidal threads (Tr) with a lift angle of less than 5° and a standard pitch.
2 Normative references
The contents of the following documents constitute essential provisions of this document by means of normative references in the text. Among them, note the date of the reference documents, only the date of the corresponding version applicable to this document; do not note the date of the reference documents, the latest version (including all the revision of the list) applicable to this document.
GB/T 14791-2013 Thread terminology
GB/T 17163 Basic terminology for geometric measuring instruments
GB/T 17164 Product terminology for geometrical measuring instruments
3 Terminology and definitions
GB/T 14791-2013,GB/T 17163,GB/T 17164 and the following terms and definitions are applicable to this document.
3.1
Metric series wires for measuring screw threads are physical gauges with accurately dimensioned cylindrical working surfaces for the indirect inspection of workpieces such as threads.
4 Types and dimensions
4.1 Type I measuring needles
The type and dimensions of the Type I measuring pin are shown in Figure 1. The illustrations are for illustrative purposes only and do not indicate the detailed structure.
4.2 Ⅱ type needle
The type and dimensions of the type II needle are shown in Fig. 2. The illustrations are for illustrative purposes only and do not show the detailed construction.
4.3 Type III needle
The type and dimensions of the Type III needle are shown in Fig. 3. The illustrations are for illustrative purposes only and do not indicate the detailed construction.
5 Requirements
5.1 Materials
The measuring needle should be made of carbon tool steel (e.g. T12A), high-carbon chromium bearing steel (e.g. GCr15), alloy tool steel or other higher performance materials such as carbide and ceramics.
5.2 Hardness of the measuring surface and surface roughness Ra
The hardness of the measuring surface should not be less than 58 HRC; the maximum permissible value of the surface roughness Ra of the measuring surface is 0.05 um.
5.3 Accuracy level and needle selection
The accuracy level of the needle is divided into О, 1, 2, the limit deviation of the nominal diameter D of a single needle, a single needle roundness tolerance, a single needle taper tolerance, the maximum tolerance of the same group of needle diameter should be in accordance with the provisions of Table 1.
The optimum selection of measuring needles for the middle diameter of common threads (M), uniform threads (UN), 55° pipe threads (G,R) and trapezoidal threads (Tr) is shown in Appendix A.
5.4 Measuring pins in groups
Measuring needles should be used in groups, usually 3 needles per group.
5.5 Needle number plate
Each group of needles should have a number plate on which the needles are suspended. The number plate should be made of steel or aluminium; the number plate should have a hole of not less than $3 mm, and the distance between the centre of the hole and the working part of the needle should be about 70 mm.
6 Test conditions and methods
6.1 Test conditions
The standard reference temperature for measuring О-grade needles is 20 °C ± 0.5 °C. The standard reference force is 0.75 N. The standard reference temperature of the measuring needle is 20 °C ± 1 °C. The standard reference force is 0.75 N. The standard reference temperature of the measuring needle is 20 °C ± 1 °C. The standard reference force is 0.75 N.
6.2 Test methods
According to the requirements of the accuracy level, choose the appropriate measuring equipment, using direct measurement method or comparative measurement method to measure the technical parameters of the measuring needle.
7 Marking and packaging
7.1 The number plate on which the needle is suspended should be marked:
a) manufacturer's name or registered trademark;
b) nominal diameter D;
c) the accuracy level.
7.2 The packaging of the needle should bear the following markings:
a) the name or registered trademark of the manufacturer;
b) Nominal diameter D;
c) the degree of accuracy;
d) the number of this document.
7.3 The needle shall be rust-proofed and properly packed before packaging and shall not be damaged during transport due to improper packaging.
7.4 The needles which have been tested to meet the requirements of this document (groups of needles) shall be accompanied by a product certificate of conformity. The product certificate of conformity shall be marked with the number of this document, the accuracy level and the date of delivery.
Appendix A (informative) commonly used thread corresponding to the choice of measuring needle
1 Scope
2 Normative references
3 Terminology and definitions
4 Types and dimensions
5 Requirements
6 Test conditions and methods
7 Marking and packaging
Appendix A (informative) commonly used thread corresponding to the choice of measuring needle
