Болты с полной и неполной резьбой: руководство по применению промышленного крепежа 

1. When to Use Full Thread Bolts

Full thread bolts excel in applications where maximum thread engagement is needed. Here are the primary scenarios:

Thin-Wall Assemblies: When clamping thin plates, sheets, or components where the total grip length is short, full threads ensure adequate engagement for proper tightening torque.

Tapped Hole Connections: When a bolt threads directly into a tapped (threaded) hole rather than using a nut, full threads provide maximum holding power within the available material depth.

Adjustment and Clamping: In fixtures, jigs, and adjustable assemblies where a bolt functions as a clamping or positioning element, full threads allow continuous adjustment along the entire length.

Shear-Dominant Joints: In connections where the bolt primarily resists shear forces rather than tensile loads, full threads perform well because the threaded cross-section engages fully with both joined members.

Small-Diameter Fasteners (< M16): For bolts and screws below M16 diameter and under 100 mm length, full threading is the manufacturing default and suits most general-purpose applications.

2. When to Use Partial Thread Bolts

Partial thread bolts are the preferred choice when joint integrity depends on precise load transfer through the bolt shank. Key application scenarios include:

Structural Steel Connections: Heavy hex bolts (ASTM A325, A490, A193 B7) used in buildings, bridges, and towers require a smooth shank to resist shear at the joint plane. The unthreaded grip section provides a full-diameter bearing surface, critical for slip-critical connections.

High-Tension Bolting (> 100 mm Length): For bolts exceeding 100 mm, partial threading reduces stress concentration at the thread root in the shear plane. The smooth shank distributes clamping force evenly across the joint members.

Piping and Flange Assemblies: Flange bolts (DIN 6921, ASME B18.2.1) use partial threading to maintain alignment accuracy in flange connections. The shank acts as a locating dowel, preventing relative movement between flanges under pressure cycling.

Rotating and Dynamic Loads: In machinery with vibration or cyclic loading, the unthreaded shank prevents fretting wear and reduces the risk of fatigue crack initiation at thread roots.

Anti-Corrosion Applications: For hot-dip galvanized (HDG), dacromet, or PTFE-coated bolts, the smooth shank accepts coating more uniformly than threaded sections, providing superior corrosion protection at the critical load-bearing zone.

Heavy Equipment and Mining: High-strength bolts (Grade 8.8, 10.9, 12.9) in excavators, crushers, and conveyor systems rely on partial thread design to handle combined shear and tensile loads in harsh environments.

3. Quick Comparison: Full Thread vs. Partial Thread