While bolts come in many styles, the industry commonly categorizes them into three primary types, based on their most essential design and usage characteristics:
1. Hex Bolts (Hex Head Bolts)
Overview
Hex bolts are the most widely used bolt type. They feature a six-sided head and are designed for general-purpose fastening in construction, machinery, automotive, and structural applications.
Key Features
Six-sided hexagon head
Available in fully threaded or partially threaded versions
Used with hex nuts and washers
Follow standards like DIN 931/933, ANSI B18.2.1, ISO 4014/4017
Common Applications
Steel structures
Machinery assembly
Construction projects
Automotive components
2. Carriage Bolts
Carriage bolts have a smooth rounded head and a square neck beneath the head. The square section locks into wood or metal to prevent spinning during tightening.
Dome (rounded) head
Square neck to prevent rotation
Designed for use in wood-to-wood or wood-to-metal connections
Timber construction
Furniture making
Fencing & outdoor structures
Automotive body panels (older models)
3. Anchor Bolts
Anchor bolts are designed to connect structures or equipment to concrete. They can be cast-in-place or installed after concrete cures.
Threaded end connects to nuts or base plates
Embedded or anchored into concrete
Includes L-shaped, J-shaped, headed, or straight anchor rods
Steel column base plates
Light poles, sign poles
Machinery foundations
Pre-engineered metal buildings
These categories represent the three most fundamental bolt functions:
Hex Bolts → General fastening
Carriage Bolts → Wood and anti-rotation fastening
Anchor Bolts → Concrete-to-steel fastening
Other bolt types exist (flange bolts, U-bolts, eye bolts, lag bolts), but the three above cover the core structural and mechanical fastening categories used globally.
