Throughbolt

Throughbolt is a type of fastener designed to pass completely through one or more workpieces, with a nut secured on the far side to clamp the parts together. It is commonly used in timber construction, furniture, and other assemblies where a strong, removable connection is required. The through bolt contrasts with blind fasteners that are designed to be concealed inside the material.

Most through bolts have a standard bolt body with a hex head or carriage bolt head, and a through hole that is drilled through the assembled pieces. The bolt may be left exposed on both sides or used with a washer and nut to spread the load. Materials include steel, stainless steel, or bronze, often with protective coatings to resist corrosion.

Installation involves aligning the parts and drilling a through hole with the correct diameter. The hole size must accommodate the bolt shank while allowing for debris and wood movement. After inserting the bolt, a washer and nut are threaded on the far side and tightened to the recommended torque, drawing the parts together without crushing the material.

Through bolts are valued for high shear strength, ease of disassembly, and straightforward replacement. They are widely used in timber framing joints, structural fittings in wooden boats, and certain furniture connections where the joint must be rebuilt or adjusted. Their main drawbacks include the need for access to both sides of the workpiece and the potential for appearance concerns on visible surfaces.

These joints illustrate a simple principle in mechanical design: through bolts allow clamping across multiple materials with removable fasteners.