GB/T 901 is a Chinese national standard specifying equal-length double-ended studs (Grade B) , commonly called double-ended bolts or full-thread studs, a common fastener in mechanical connection. In terms of properties, it has equal-length threads at both ends and a smooth rod in the middle (divided into thick-rod Type A and thin-rod Type B) without a head. Common materials include Q235 carbon steel (Grade 4.8-6.8), 40Cr alloy steel (Grade 8.8-10.9) and 304 stainless steel. Its surface is treated with galvanizing, blackening, etc. The thread diameter ranges from M2 to M56, the length is customized on demand, and Grade B precision ensures interchangeability.
Its features include easy installation—no welding or pre-drilling required; both ends can be directly screwed into connectors to match nuts, suitable for space-constrained scenarios. The double-threaded sections transmit loads, with high tensile strength (Grade 10.9 reaches 1040MPa) and good vibration resistance. It replaces the bolt + nut combination, saving cost and time. Thick and thin rod types adapt to different load requirements, and stainless steel material is corrosion-resistant.
It is widely used:
Connecting gearboxes and bearing housings in machinery manufacturing; fixing high-pressure valves and flanges in power engineering; applied to steel structure joints in construction; assembling engine blocks and decks in automotive and marine industries; and 316 stainless steel can be used in special scenarios like oil drilling to resist corrosion.
| Screw Thread | M2 | M2.5 | M3 | M4 | M5 | M6 | M8 | M10 | M12 | (M14) | M16 | (M18) | |
| d | |||||||||||||
| P ① | Pitch | 0.4 | 0.45 | 0.5 | 0.7 | 0.8 | 1 | 1.25 | 1.5 | 1.75 | 2 | 2 | 2.5 |
| Weight of per 1000 steel products(≈kg) | - | ||||||||||||
| Length of Thread b | - | ||||||||||||
| Screw Thread | M20 | (M22) | M24 | (M27) | M30 | (M33) | M36 | (M39) | M42 | M48 | M56 | ||
| d | |||||||||||||
| P ① | Pitch | 2.5 | 2.5 | 3 | 3 | 3.5 | 3.5 | 4 | 4 | 4.5 | 5 | 5.5 | |
| Weight of per 1000 steel products(≈kg) | - | ||||||||||||
| Length of Thread b | - | ||||||||||||
| ①,P = pitch of coarse thread. ②,diameter of the unthreaded shank ≈ pitch diameter of thread ③,Xmax = 1.5P | |||||||||||||
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