Bolts are one of the most common types of fasteners used in construction and engineering. Though small in size, bolts play an immense role in holding together large structures. In this article, we will delve into the various types of bolts, their uses, strengths and limitations.
Types of Bolts
There are several different types of bolts used for various applications. Some of the main types are:
Carriage bolts have a dome head on one side and a square section under the head. This allows them to be inserted from one side and turned with a wrench. They are commonly used to join wood structures like furniture together.
Lag bolts, also called lag screws, have a square drive head and coarse threads along most of their shaft. They are designed to grip wood and are often used to connect wood to concrete or masonry. Their threads help them bind securely into softer materials.
Machine bolts are general purpose bolts with strength suitable for most mechanical applications. They have cylindrical shafts without any distinctive features. Hexagonal or square nuts are used on machine bolts to secure components.
Stove Bolts are very similar to machine bolts but have a thinner shank to facilitate tightly spaced installations. They are commonly used in appliances, machinery and other compact assemblies.
Cap screws are heavy-duty bolts with a head on one end and a shaped drive feature like a hex on the other end. They can be driven into place and tightened securely from either end. Cap screws are used in demanding applications.
Each type of bolt is designed to fulfill specific requirements in terms of strength, function and compatible materials. Proper selection of bolts is important for reliability and safety of structures.
Most bolts are made of steel owing to its ideal combination of strength, corrosion resistance and cost effectiveness. Common steel types used are carbon steel, alloy steel and stainless steel.
Carbon steel bolts offer good strength at low cost but are prone to rusting. Alloy steels have improved strength, toughness and corrosion resistance over carbon steel. Stainless steel bolts have excellent corrosion resistance for demanding environments.
The metallurgy of bolts determines their key properties. Proper composition allows bolts to withstand sustained tensile loads, shear forces, vibrations and environmental degradation.
Bolt steels offer attributes like:
High tensile strength – Ability to withstand heavy loads without failing.
Toughness – Resistance to impact and shock loading.
Hardness – Resistance to wear, scratches and damage.
Durability – Long operational life in harsh conditions.
Corrosion resistance – Protection from rusting and chemical damage.
By controlling factors like carbon content, additional alloying elements and heat treatment processes, manufacturers precisely tune bolt properties for target applications. This metallurgical design is crucial for reliable mechanical performance.
Installation and Maintenance
Correct bolt installation procedure involves several steps for optimal service. Some best practices include:
Using the correct bolt size, grade and length as specified in designs.
Cleaning mating surfaces to remove contaminants before assembly.
Applying thread locking agents or lubricants if specified.
Tightening bolts in a star or circular pattern gradually to required torques.
-nspecting for proper engagement without loosening after installation.
Bolted joints may require occasional maintenance for long life. Key steps are:
Regularly checking for signs of wear, damage or cracks in the bolt shaft or head.
Retightening bolts that have slackened with time due to stress relaxation.
Replacing bolts that show substantial corrosion or other deterioration.
Applying protective coatings periodically on bolts in corrosive locations.
Following any replacement recommendations from equipment manuals.
Proper installation and preventive maintenance practices prevent premature bolt failures and associated downtime or accidents.
Common Bolt Failures
Subheadings: Overloading, Corrosion and Fatigue
Exceeding the rated load capacity of a bolt is a major cause of failure. Symptoms include permanent plastic deformation, necking and fractures of the shaft or head. Overloading can occur due to incorrect specifications, excessive external forces or poor load distribution.
Corrosion weakens bolts through rusting or chemical attack over time when installed in corrosive surroundings. Failure happens after the thinning metal cross-section can no longer support loads. Stainless or coated bolts prevent corrosion failures.
Loading cycles place repetitive stresses on bolts, eventually causing microscopic cracks to form around the shaft or under the head. These propagate with each cycle until the bolt suddenly fractures, even at loads under rated capacity. Proper torqueing and preload distribution reduces stress concentrations and fatigue damage.
Bolts play an indispensable yet underappreciated role in keeping our world’s infrastructure and machinery functioning safely. While simple in appearance, bolts merit careful consideration in their material choice, design installation, maintenance and replacement practices. Adhering to proven bolting solutions and standards ensures bolts serve their intended purpose reliably for years to come. With humbler components like bolts working smoothly behind the scenes, we can focus on bigger achievements ahead.
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it