AS NZS 4291.2:2016 pdf download.Mechanical properties of fasteners made of carbon steel and alloy steel Part 2: Nuts with specified property classes——Coarse thread and fine pitch thread.
4 Designation systems
4.1 Designation of nut styles
This part of ISo 898 specifies requirements for three styles of nuts according to their height: 一style 2: high nut with minimum height mmin≈0,9D or mmin > 0,9D; see Table A.1; 一style 1: regular nut with minimum height mmin≥0,8D; see Table A.1; 一style 0: thin nut with minimum height 0,45D≤mmin < 0,8D.
4.2 Designation of property classes
4.2.1 General
The marking and labelling of nuts with property classes shall be as specified in Clause 10 for only those nuts which meet all applicable requirements of this part of ISO 898.
4.2.2 Regular nuts (style 1) and high nuts (style 2)
The symbol for property classes of regular nuts (style 1) and high nuts (style 2) consists of one number. It corresponds to the number to the left of the appropriate maximum property class of bolts, screws and studs with which they can be mated.
4.2.3 Thin nuts (style 0)
The symbol for property classes of thin nuts (style 0) consists of two numbers, specified in the following ways:
a) the first number is zero, indicating that the loadability of the nut is reduced in comparison with the loadability of a regular nut or a high nut according to 4.2.2 and therefore thread stripping can occur when overloaded;
b) the second number corresponds to 1/100 of the nominal stress under proof load on a hardened test mandrel, in megapascals.
4.3 Ranges of nominal diameters in relation to nut style and property class
The ranges of nominal diameters in relation to nut style and property class are as given in Table 1.
5 Design of bolt and nut assemblies
Explanations of basic design principles of nuts and loadability of bolted assemblies are given in Annex A. Regular nuts (style 1) and high nuts (style 2) shall be mated with externally threaded fasteners according to Table 2. However, nuts of a higher property class may replace nuts of a lower property class.
A decrease of thread stripping strength occurs for nuts with a fundamental deviation greater than zero for tolerance class 6H (such as hot dip galvanized nuts: 6AZ, 6AX). Thin nuts (style 0) have a reduced loadability compared to regular nuts or high nuts, and are not designed to provide resistance to thread stripping. Thin nuts used as jam nuts should be assembled together with a regular nut or a high nut. In assemblies with jam nut, the thin nut is first tightened against the assembled parts and then the regular or high nut is tightened against the thin nut.
6 Materials
Table 3 specifies materials and heat treatment for the different property classes of nuts. Nuts with coarse thread and property classes 05, 8 [regular nuts (style 1) with D > M16], 10 and 12 shall be quenched and tempered. Nuts with fine pitch thread and property classes 05, 6 (with D > M16), 8 [regular nuts (style 1)], 10 and 12 shall  be quenched and tempered. The chemical composition shall be assessed in accordance with the relevant International Standards.
NOTE It is intended that national regulations for the restriction or prohibition of certain chemical elements be taken into account in the countries or regions concerned.
7 Mechanical properties
When tested by the methods specified in Clause 9, the nuts of the specified property class shall meet, at ambient temperature, the requirements for the proof load (see Tables 4 and 5) and for the hardness (see Tables 6 and 7), regardless of which tests are performed during manufacturing or final inspection. For nuts which are not quenched and tempered, 9.2.4.2 additionally applies.
8 Inspection
8.1 Manufacturer’s inspection
This part of ISO 898 does not mandate which of the tests the manufacturer shall perform on each manufacturing lot. It is the responsibility of the manufacturer to apply suitable methods of his choice, such as in-process testing or inspection to ensure that the manufactured lot does indeed conform to all of the specified requirements. For additional information, see ISO 16426. In case of dispute, the test methods according to Clause 9 shall apply.
8.2 Supplier’s inspection
The supplier tests the nuts which he provides using methods of their choice (periodic evaluation of the manufacturer, checking of test results from the manufacturers, tests on the nuts, etc.), provided the mechanical and physical properties specified in Tables 3, 4, 5, 6 and 7 are met. In case of dispute, the test methods according to Clause 9 shall apply.
8.3 Purchaser’s inspection
The purchaser may test the delivered nuts using the test methods specified in Clause 9. In case of dispute, the test methods according to Clause 9 shall apply, unless otherwise specified.AS NZS 4291.2 pdf download.

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