This standard specifies the technical requirements, inspection rules, marking and packaging of main bearing cap bolts and nuts for internal combustion engines. This standard applies to main bearing cap bolts and nuts for internal combustion engines with a cylinder diameter less than or equal to 200mm. JB/T 7293-1994 Technical requirements for main bearing cap bolts and nuts for internal combustion engines JB/T7293-1994 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T7293-94
Internal combustion engine main bearing cover bolts and nuts
Technical conditions
Published on July 18, 1994
Ministry of Machinery Industry of the People's Republic of China
Implementation on July 1, 1995
Mechanical Industry Standard of the People's Republic of China
Internal combustion engine main bearing cover bolts and nutsWww.bzxZ.net
Technical conditions
1 Subject content and applicable scope
JB/T7293--94
This standard specifies the technical requirements, inspection rules, marking and packaging of internal combustion engine main bearing cover bolts and nuts. This standard applies to the bolts and nuts (hereinafter referred to as bolts and nuts) of the main bearing caps of internal combustion engines with a cylinder diameter less than or equal to 200 mm.
2 Reference standards
GB1167
Acceptance inspection, marking and packaging of fasteners
Ordinary thread tolerances and fits (diameter 1~355mm) Transition fit threads (screwed into cast iron, steel body) Mechanical properties of complex fasteners Bolts, screws and studs GB3098.1
GB 3098.4
Mechanical properties of fasteners Fine pitch nuts
Fastener tolerances Bolts, screws and nuts
Surface defects of fasteners General requirements for bolts, screws and studs
GB5779.2 Surface defects of fasteners Nuts - General requirements 3 Technical requirements
Bolts and nuts shall comply with the requirements of this standard and be manufactured according to product drawings and technical documents approved through the prescribed procedures. 3.2 Bolt materials shall comply with the provisions of Table 2 of GB3098.1, and nut materials shall comply with the provisions of Table 3 of GB3098.4. 3.3 The mechanical properties of bolts shall comply with the provisions of GB3098.1, and their performance level shall be equal to or higher than Grade 8.8: The mechanical properties of nuts shall comply with the provisions of GB3098.4, and their performance level shall be equal to or higher than Grade 8. 3.4 The thread tolerance of bolts and nuts shall comply with Grade 6 specified in GB197, and the transition fit thread of the bolt screwed into the body end shall comply with the first fit tolerance specified in GB1167.
3.5 The verticality tolerance value of the bolt head bearing surface to the thread axis is less than or equal to 0.08mm. 3.6
The coaxiality tolerance value of the bolt shank axis to the thread axis shall comply with the provisions of Grade A products in GB3103.1. The verticality tolerance value of the end nut bearing surface to the thread axis shall be less than or equal to 0.1mm. -3.7
The coaxiality tolerance of the hexagonal body of the nut to the thread minor diameter is selected as 2IT12 grade according to the width of the opposite side. The surface roughness requirements of each part of the bolt are as follows: 3.9
The head bearing surface R. is 3.2μm#
The shank surface R. is 3.2μm;
The thread surface R. is 1.6μm,
3.10The surface roughness requirements of each part of the nut are as follows: a. The bearing surface R is 3.2μm;
b, the thread surface R. is 3.2μm.
3.11The shank, thread part and head bearing surface of the bolt are not allowed to have defects such as burrs and rust. Under the condition that the thread can be screwed in normally, the Ministry of Machinery Industry approved it on July 18, 1994 and implemented it on July 1, 1995, and incomplete threads are allowed to exist at the two ends of the thread. JB/T7293-94
Nut bearing surface and threaded part are not allowed to have defects such as burrs and rust. 3.12
3.13 Bolts and nuts should be oxidized or treated with other anti-rust treatments. 3.14 Other technical requirements shall be in accordance with the provisions of GB3103.1 and GB5779.1.GB5779.2. Inspection rules
4.1 Products shall be inspected and qualified by the quality inspection department of the manufacturer before they can leave the factory. 4.2 When the ordering unit samples the product quality, it shall be carried out in accordance with the provisions of GB90. 4.3 Other surface defects of bolts and nuts shall be carried out in accordance with the provisions of GB5779.1 and GB5779.2. Marking and packaging
Marking and packaging shall comply with the provisions of GB90. Additional remarks:
This standard is proposed and managed by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. This standard is drafted by the Shanghai Internal Combustion Engine Research Institute, and the main drafter of this standard is Du Rong.
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