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ASME B18.31.2 Continuous Thread Double End Full Body Studs
Double-ended threaded studs with continuous threading options, designed for secure and precise flange connections in pressure vessels and piping systems.
ASME B18.31.2 Continuous Thread Double End Full Body Studs are specialized fasteners consisting of a cylindrical bar threaded on both ends, often with a continuous thread running the entire length or a specific unthreaded shank portion depending on the variation. Unlike standard stud bolts which may have a short thread transition, these are designed for applications requiring precise length control and uniform stress distribution across the fastener. They are predominantly used in the oil and gas, petrochemical, and power generation industries to connect pipe flanges, valve bonnets, and pressure vessel closures. The "full body" designation indicates that the nominal diameter is maintained throughout the length, ensuring maximum strength and stiffness. Compliance with ASME B18.31.2 ensures that the thread lengths, end configurations, and overall dimensions are standardized, facilitating easy assembly and disassembly during maintenance operations in critical process systems.
ASME B18.31.2 Dimensions for Continuous Thread Studs (Inch)
| Nominal Size | Diameter, D | Chamfered Thread Distance, U | |||||
|---|---|---|---|---|---|---|---|
| UNC Threads | UNF Threads | 8UN Threads | |||||
| Min. | Max. | Min. | Max. | Min. | Max. | ||
| 1/4 | 0.2500 | 0.050 | 0.100 | 0.036 | 0.071 | … | … |
| 5/16 | 0.3125 | 0.056 | 0.111 | 0.042 | 0.083 | … | … |
| 3/8 | 0.3750 | 0.063 | 0.125 | 0.042 | 0.083 | … | … |
| 7/16 | 0.4375 | 0.072 | 0.143 | 0.050 | 0.100 | … | … |
| 1/2 | 0.5000 | 0.077 | 0.154 | 0.050 | 0.100 | … | … |
| 9/16 | 0.5625 | 0.084 | 0.167 | 0.056 | 0.111 | … | … |
| 5/8 | 0.6250 | 0.091 | 0.182 | 0.056 | 0.111 | … | … |
| 3/4 | 0.7500 | 0.100 | 0.200 | 0.063 | 0.125 | … | … |
| 7/8 | 0.8750 | 0.111 | 0.222 | 0.072 | 0.143 | … | … |
| 1 | 1.0000 | 0.125 | 0.250 | 0.084 | 0.167 | … | … |
| 1 1/8 | 1.1250 | 0.143 | 0.286 | 0.084 | 0.167 | 0.125 | 0.250 |
| 1 1/4 | 1.2500 | 0.143 | 0.286 | 0.084 | 0.167 | 0.125 | 0.250 |
| 1 3/8 | 1.3750 | 0.167 | 0.333 | 0.084 | 0.167 | 0.125 | 0.250 |
| 1 1/2 | 1.5000 | 0.167 | 0.333 | 0.084 | 0.167 | 0.125 | 0.250 |
| 1 5/8 | 1.6250 | … | … | … | … | 0.125 | 0.250 |
| 1 3/4 | 1.7500 | 0.200 | 0.400 | … | … | 0.125 | 0.250 |
| 1 7/8 | 1.8750 | … | … | … | … | 0.125 | 0.250 |
| 2 | 2.0000 | 0.222 | 0.444 | … | … | 0.125 | 0.250 |
| 2 1/4 | 2.2500 | 0.222 | 0.444 | … | … | 0.125 | 0.250 |
| 2 1/2 | 2.5000 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
| 2 3/4 | 2.7500 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
| 3 | 3.0000 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
| 3 1/4 | 3.2500 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
| 3 1/2 | 3.5000 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
| 3 3/4 | 3.7500 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
| 4 | 4.0000 | 0.250 | 0.500 | … | … | 0.125 | 0.250 |
ASME B18.31.2 Continuous Thread and Double-End Stud Length Tolerances (Inch)
| Range, LT | Continuous-Thread Studs |
|---|---|
| From ¾ through 2½ | ±0.04 |
| Over 2½ through 4 | ±0.08 |
| Over 4 through 8 | ±0.10 |
| Over 8 through 16 | ±0.12 |
| Over 16 | ±0.18 |
Frequently Asked Questions
- What does ASME B18.31.2 double-end full-body studs cover?
- ASME B18.31.2 is the inch dimensional standard for double-end full-body studs. It defines head dimensions, body diameter, thread length, total length, drive recess, and tolerances so any compliant double-end full-body studs interchanges with standard nuts, washers and wrenches across manufacturers.
- What size range is available for double-end full-body studs under ASME B18.31.2?
- double-end full-body studs under ASME B18.31.2 covers 1/4 in to 4 in nominal diameter, full unthreaded body with both ends threaded. TorqBolt manufactures the full range in ASTM A193 Grades B7, B7M, B8, B8M and the full ASTM A320 cryogenic counterpart on customer specification.
- What is the metric/inch counterpart of ASME B18.31.2 double-end full-body studs?
- The companion specification for double-end full-body studs is ASME B18.31.1M metric clamping studs. Both standards share equivalent functional dimensions but use the corresponding measurement system (inch vs metric ISO M-series).
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