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GB/T 30986 consists of the following parts, under the general title Mechanical Properties of Fasteners:
— GB/T 3098.1 Mechanical Properties of Fasteners — Blots, Screws and Studs;
— GB 3098.2-2 Mechanical Properties of Fasteners — Nuts;
— GB/T 3098.3 Mechanical Properties of Fasteners — Set Screws;
— GB/T 3098.5 Mechanical Properties of Fasteners — Tapping Screws;
— GB/T 3098.6 Mechanical Properties of Fasteners — Stainless Steel Bolts, Screws and Studs;
— GB/T 3098.7 Mechanical Properties of Fasteners — Thread Rolling Screws;
— GB/T 3098.8 Mechanical Properties of Fasteners — Parts for Bolted Connections for Use at Temperatures from -200°C ~ +700°C;
— GB/T 3098.9 Mechanical Properties of Fasteners — Prevailing Torque Type Steel Nuts;
— GB/T 3098.10 Mechanical Properties of Fasteners — Bolts, Screws, Studs and Nuts Made of Non-Ferrous Metals;
— GB/T 3098.11 Mechanical Properties of Fasteners — Drilling Screws with Tapping Screw Thread;
— GB/T 3098.12 Mechanical Properties of Fasteners — Cone Proof Load Test on Nuts;
— GB/T 3098.13 Mechanical Properties of Fasteners — Torsional Test and Minimum Torques for Bolts and Screws with Nominal Diameters 1mm to 10mm;
— GB/T 3098.14 Mechanical Properties of Fasteners — Widening Test on Nuts;
— GB/T 3098.15 Mechanical Properties of Fasteners — Stainless Steel Nuts;
— GB/T 3098.16 Mechanical Properties of Fasteners — Stainless Steel Set Screws;
— GB/T 3098.17 Mechanical Properties of Fasteners — Preloading Test for the Detection of Hydrogen Embrittlement — Parallel Bearing Surface Method;
— GB/T 3098.18 Mechanical Properties of Fasteners — Blind Rivets Testing;
— GB/T 3098.19 Mechanical Properties of Fasteners — Blind Rivets with Break Pull Mandrel;
— GB/T 3098.20 Mechanical Properties of Fasteners — Wing Nuts with Specified Proof Torque;
— GB/T 3098.21 Mechanical Properties of Fasteners — Stainless Steel Tapping Screws;
— GB/T 3098.22 Mechanical Properties of Fasteners Made of the Fine Grain Non-heat Treatment Steel — Bolts, Screws and Studs;
— GB/T 3098.23 Mechanical Properties of Fasteners — M42 ~ M72 Blots, Screws and Studs;
— GB/T 3098.24 Mechanical Properties of Fasteners — Stainless Steel Bolts, Screws and Studs for Heat Resistance and High Temperature Applications;
— GB/T3098.25 Mechanical Properties of Fasteners — Guideline for Selection of Stainless Steel and Nickel Alloy Steel Fasteners.
This part is Part 9 of GB/T 3098.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 3098.9-2010 Mechanical Properties of Fasteners — Prevailing Torque Type Steel Nuts in whole.
The following technical deviations have been made with respect to GB/T 3098.9-2010 (the previous edition):
— nuts of property class 9 have been deleted (see Tables 6 and 9 of Edition 2010);
— prevailing torques for nuts M3 and M4 have been moved to annex (see Annex C);
— the surface condition of the reference test bolt/screw has been specified in accordance with GB/T 16823.3 (see 9.3.2);
— the threaded length of the end of the test bolt/screw protrude through the nut is changed from “4 to 7 pitches” to “3 to 5 pitches” (see Figure 1 and 9.3.4);
— the determination method of the prevailing off torque has been changed (see Figure 2, point 5).
This standard has been redrafted and modified adoption of International Standard ISO 2320:2015 Fasteners — Prevailing Torque Steel Nuts — Functional Properties.
compared with ISO 2320: 2015, the technical differences in this part and their causes are as follows:
— the international standards in Normative References (see Clause 2) are replaced by corresponding Chinese standards, in order to comply with the basic standards of fasteners in China;
— "equal to 80% of the proof load of property class 4.8 bolts for D > 24 mm" is added in footnote a to comply with the production practice (see Table 3).
For the purposes of this part, the following editorial changes have also been made:
— the title of this standard is changed.
This part was proposed by the China Machinery Industry Federation.
This part is under the jurisdiction of SAC/TC 85 (National Technical Committee 85 on Fasteners of Standardization Administration of China).
SAC/TC 85 is responsible for the explanation of this part.
The previous editions of this part are as follows:
— GB/T 3098.9-1993, GB/T 3098.9-2002, GB/T 3098.9-2010;
— GB/T 928-1980.
Mechanical Properties of Fasteners — Prevailing Torque Type Steel Nuts
1 Scope
This part of GB/T 3098 specifies the functional properties for prevailing torque steel nuts when tested at an ambient temperature range of +10°C to +35°C. It includes a combined test method to determine the prevailing torque properties and the torque/clamp force properties at the same time.
This part is applicable to prevailing torque all metal type nuts and prevailing torque non-metallic insert type nuts:
— with general purpose metric screw threads in accordance with GB/T 192;
— with diameter/pitch combination in accordance with GB/T 193 and GB/T 9144;
— with coarse pitch thread M5 to M39 or with fine pitch thread of nominal diameter d = 8 mm to 39 mm;
— with thread tolerances in accordance with GB/T 9145;
— with mechanical properties in accordance with GB/T 3098.2.
Prevailing torque values specified in this part are based on laboratory test conditions.
Note 1: Actual prevailing torques in practical application can vary.
Note 2: All metal type nuts conforming to the requirements of this part are used in applications ranging from -50°C to +150°C.
Note 3: Non-metallic insert type nuts conforming to the requirements of this part are used in applications ranging from -50°C to +120°C.
Warning: Temperatures outside the ambient temperature range can influence the functional properties (torque/clamp force and prevailing torque properties). See annex A.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 3098.1 Mechanical Properties of Fasteners — Bolts, Screws and Studs (GB/T 3098.1-2010, ISO 898-1: 2009, MOD)
GB/T 3098.2 Mechanical Properties of Fasteners — Nuts (GB/T 3098.2-2010, ISO 898-2:2012, MOD)
GB/T 5277 Fasteners — Clearance Holes for Bolts and Screws (GB/T 5277-1985, eqv ISO 273:1979)
GB/T 9145 General Purpose Metric Screw Threads — Limits of Sizes for the Screw Threads of Medium Quality and Preferable Plan (GB/T 9145-2003, ISO 965-2: 1998, MOD)
GB/T 16823.3 Fasteners — Torque/Clamp Force Testing (GB/T 16823.3-2010, ISO 16047:2005, IDT)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 16823.3 and the following apply.
3.1
prevailing torque nut
nut which is not free-running on a mating thread by virtue of a self-contained prevailing torque feature, and which provides resistance to rotation independent of clamping or compression forces
3.2
prevailing torque developed by the nut
torque necessary to rotate the nut on its mating externally threaded component and without clamp force
3.3
prevailing-on torque
torque to rotate the nut on its mating externally threaded component with the torque measured while the nut is in motion and without clamp force
3.4
prevailing-off torque
torque to rotate after backing off the nut until the removal of the clamp force in the following 360° rotation of the nut
3.5
prevailing torque all metal type nut
nut which has a one piece or a multiple piece metal construction and derives its prevailing torque characteristics from a controlled distortion of the nut thread and/or body and/or from metallic insert(s)
3.6
prevailing torque non-metallic insert type nut
nut which has a multiple piece construction and derives its prevailing torque characteristics from insert(s) of non-metallic material retained in the nut
3.7
seating point
point in the tightening process where clamp force first appears
4 Symbols
For the purpose of this document, the symbols given in GB/T 16823.3 and the followings apply.
D nominal diameter, in millimetres (s)
d4 diameter of the hole of the fixture, in millimetres (s)
Fp proof load, in newtons (N)
F65 lower load limit for the evaluation of the coefficient of total friction, newtons (N)
F75 upper load limit for the evaluation of the coefficient of total friction, newtons (N)
F80 test clamp force (shut-down force for the tightening process), in newtons (N)
P pitch of the thread, in millimetres (mm)
TFV prevailing-on torque, in newton metres (N·m)
TFd prevailing-off torque, in newton metres (N·m)
T65 lower torque limit for the evaluation of the coefficient of total friction, in newton metres (N·m)
T75 upper torque limit for the evaluation of the coefficient of total friction, in newton metres (N·m)
T80 test torque corresponding to 80% of the proof load, in newton metres (N·m)
μtot coefficient of total friction
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5 Thread
Threads for prevailing torque nuts shall be in accordance with GB/T 9145 except for the prevailing torque feature:
a) for prevailing torque non-metallic insert type nuts, the GO gauge shall be suitable for free installation (by hand) until it is seated against the prevailing torque feature;
b) for prevailing torque all metal type nuts, the GO gauge shall be suitable for free installation (by hand) to one pitch at least.
6 Lubrication
At the option of the manufacturer, a lubricant may be applied to the manufacturing lot to fulfil the functional requirements.
Foreword II
1 Scope
2 Normative References
3 Terms and Definitions
4 Symbols
5 Thread
6 Lubrication
7 Mechanical Properties of Prevailing Torque Nuts
8 Functional Requirements for Prevailing Torque Properties
9 Test Method
Annex A (Normative) Temperature Influence on Prevailing Torques of Nuts with Non-metallic Insert
Annex B (Informative) Principles for the Evaluation of the Total Coefficient of Friction, μtot
Annex C (Informative) Test Clamp Force and Prevailing Torques for Prevailing Torque Nuts M3 and M4 in Property Classes 8 and
Bibliography
