Key Characteristics of Hex Bolts
Hexagonal Head:
The defining feature of hex bolts is their six-sided head, which allows for easy gripping with
wrenches or socket tools from different angles.
This head shape is ideal for delivering high
torque during installation or removal.
Full or Partial Threading:
Fully Threaded:
These hex bolts have threads running along their entire length, making them
suitable for fastening in materials where the grip length is not a concern, like in joining thin
materials or for adjustable fittings.
Partially Threaded: Hex bolts with a portion of unthreaded shank between the head and the
threads offer greater tensile strength and are used when shear resistance is required, such as
in load-bearing applications.
Material:
Hex bolts come in various materials to suit different applications:
Carbon Steel: The most common material for hex bolts, carbon steel offers high tensile strength
and durability.
Stainless Steel: Known for its excellent corrosion resistance, stainless steel hex bolts are
used in environments exposed to moisture or chemicals.
Alloy Steel: These bolts provide superior strength and are heat-treated for use in high-stress
or high-temperature conditions.
Brass or Bronze: These non-magnetic, corrosion-resistant materials are often used in electrical
or marine applications.
Titanium: Lightweight yet strong, titanium hex bolts are ideal for aerospace and medical
applications requiring high strength and corrosion resistance.
Finishes:
Hex bolts come in various surface finishes to improve their corrosion resistance and longevity:
Zinc Plated: A common finish that provides moderate corrosion resistance, suitable for indoor
applications.
Hot-Dip Galvanized: Offers superior rust resistance, ideal for outdoor or wet environments.
Black Oxide: Adds a dark, matte appearance and mild corrosion resistance.
Nickel or Chrome Plated: Provides a polished, decorative look while offering additional
corrosion resistance.
Thread Type:
Hex bolts are available with different thread types to match the application’s needs:
Coarse Threads (UNC): These are widely used for general-purpose applications as they are more
resistant to stripping and easier to install.
Fine Threads (UNF): Provide better strength and are used in applications requiring higher
precision or greater tensile strength.
Metric Threads: Used in applications requiring metric measurement standards, these threads are
common in European and international manufacturing.
Types of Hex Bolts
Heavy Hex Bolts:
Description: These bolts feature a larger, thicker head than standard hex bolts, making them
suitable for heavy-duty applications where extra torque is required.
Use Case: Heavy hex bolts are used in structural, industrial, and infrastructure applications
where high tensile strength and durability are needed.
Applications: Bridge construction, heavy equipment, and steel structures.
Hex Lag Bolts (Lag Screws):
Description: These are large, heavy-duty fasteners with a hex head and coarse threads, designed
for driving into wood or masonry without the need for a nut.
Use Case: Lag bolts are used for wood-to-wood and wood-to-metal applications, typically in
outdoor or load-bearing structures.
Applications: Deck construction, wooden beams, and outdoor structures.
Tap Bolts:
Description: Tap bolts are fully threaded hex bolts, making them suitable for applications where
the bolt needs to engage with threading over its entire length.
Use Case: Used for fastening into pre-threaded holes or nuts, often in metalworking and
machinery applications.
Applications: Securing metal panels, automotive parts, and machinery assemblies.
Flange Bolts:
Description: Hex flange bolts have an integrated washer-like flange under the head that
distributes pressure and eliminates the need for a separate washer.
Use Case: Ideal for securing materials where vibration might be an issue, as the flange provides
a stable grip.
Applications: Automotive frames, engine components, and heavy-duty machinery.
Hex Machine Bolts:
Description: These are standard hex bolts used for fastening metal components together,
typically paired with a nut and washer.
Use Case: Suitable for general-purpose applications in machinery, construction, and
infrastructure.
Applications: Metalworking, construction, and agricultural machinery.
Specifications of Hex Bolts
Thread Size:
Hex bolts come in various thread sizes depending on the application. Common imperial sizes range
from 1/4 inch to 1-1/2 inches in diameter, while metric sizes range from M5 to M48.
Length:
Available in different lengths depending on the application, typically ranging from 1/2 inch to
6 inches for standard bolts and longer for specific applications.
Tensile Strength:
Hex bolts must meet specific strength standards depending on their material.
For example, grade
8 hex bolts (alloy steel) have a minimum tensile strength of 150,000 psi, while grade 5 bolts
(medium carbon steel) offer a tensile strength of 120,000 psi. Stainless steel hex bolts provide
a tensile strength of 70,000 to 100,000 psi.
Standards:
Hex bolts are produced in line with specific standards to ensure uniformity in quality and
performance:
ASTM A307: For carbon steel hex bolts.
ASTM A325: For high-strength structural bolts.
ASTM A490: For heavy hex bolts made from alloy steel.
ISO 4014/4017: International standards for hex bolts and screws.
Applications of Hex Bolts
Construction and Infrastructure:
Hex bolts are commonly used in building bridges, skyscrapers, and other infrastructure due to
their strength and reliability. Heavy hex bolts are particularly used in load-bearing
structures.
Examples: Securing steel beams, metal plates, and structural components.
Machinery and Equipment:
In industrial machinery and equipment, hex bolts provide the clamping force needed to hold heavy
parts together. Their precise threading and durability make them suitable for dynamic and
high-load environments.
Examples: Engine components, heavy machinery, and conveyors.
Automotive Industry:
The automotive sector uses hex bolts in various parts, including engine assemblies, frames, and
suspensions. Their ability to handle torque and vibrations makes them ideal for these demanding
applications.
Examples: Securing engine blocks, transmission systems, and vehicle frames.
Woodworking and Carpentry:
Hex lag bolts are commonly used in woodworking and carpentry projects, especially for outdoor
and structural applications where high strength and long-lasting durability are important.
Examples: Decking, fencing, and timber-framed structures.
Oil and Gas Industry:
In oil refineries, offshore platforms, and other oil and gas industry applications, hex bolts
made from corrosion-resistant materials like stainless steel or galvanized steel are used to
secure pipelines, flanges, and equipment.
Examples: Securing oil rigs, refineries, and industrial equipment.
Aerospace and Marine Applications:
Hex bolts made from titanium or stainless steel are used in aerospace and marine environments
due to their lightweight, high-strength, and corrosion-resistant properties.
Examples: Aircraft structures, shipbuilding, and underwater equipment.