What are the differences between full-threaded bars and double-ended studs

1. Basic definitions and structural features

The full-threaded thread bar, as a rod-shaped fastener with full-body threading, has a thread coverage rate of up to 100%, and typical specifications include metric thread profiles of M6-M48. This continuous threaded structure makes it perform well in scenarios where the connection thickness is adjustable, such as the adjustment of beam-column joints in steel structures. The double-ended stud adopts a "dumbbell-shaped" design with threads at both ends and a smooth rod in the middle. The length of the middle section without threads is usually 1.5 times the thread diameter. This structure gives it an advantage in flange connections that require preload. The international standards ISO 4014 and ISO 4032 respectively make detailed provisions for the two types of products.

2. Comparison of the five core performances

Load-bearing capacity difference: Due to the significant reduction in cross-section, the tensile strength of fully threaded bars is usually 15% to 20% lower than that of double-ended studs of the same specification. ASTM A193 B7 standard shows that the ultimate load of M20 double-ended studs can reach 24.5 tons, while that of the same-level fully threaded parts is approximately 20 tons.

Anti-loosening performance comparison: The smooth rod section of the double-ended stud can be equipped with anti-loosening devices such as hydraulic nuts, and it performs better in a vibrating environment. The case of wind power tower tube connection shows that the node loosening rate using double-ended studs is 40% lower than that of the all-threaded scheme.

Installation efficiency data: The full-threaded strips can achieve interlocking at any position. In scenarios such as pipe supports that require frequent adjustments, the installation time is reduced by 30% compared to double-ended studs. However, the pre-assembly feature of double-ended studs can increase work efficiency by 25% in automotive production lines.

Corrosion protection performance: Hot-dip galvanized full-threaded parts are prone to coating peeling off in the threaded interlocking area, while the smooth rod section of double-ended studs can maintain a complete coating. Salt spray tests show that under the same treatment process, the corrosion resistance life of double-headed studs is extended by 50%.

Maintenance cost analysis: The maintenance data of petrochemical equipment shows that the average replacement time for full-threaded threads is 2.1 working hours per piece, and for double-ended studs, which require special disassembly tools, the average replacement time is 3.5 working hours per piece.

3. Analysis of Typical Application Scenarios

The main field of fully threaded braces:

Building curtain wall adjustment system (adjustable to ±15mm)

Angle adjustment mechanism for solar brackets

Parallelism adjustment of injection molding machine templates

Advantages of double-headed studs:

High-pressure vessel flange sealing (requires a preload of more than 20,000N)

Engine block assembly (requiring consistency in axial stiffness)

Bridge bearing fixation (Anti-vibration and loosening requirements)

4. Procurement Decision Tree Guide

Provide a visual selection flowchart:

(1) Is frequent adjustment necessary? Yes → Select full thread

(2) Does it bear alternating loads? Yes → Choose double-headed

(3) Is it necessary for the sealing pressure to be greater than 1.6MPa? Yes → Choose double-headed

(4) Is there any budget constraint? Yes → Select full thread