Different Types of Bolts and Their Uses
Bolts are one of the most common types of fasteners used in engineering and construction. They are threaded fasteners that are inserted through holes in the materials being joined and held in place by a mated nut threaded onto the bolt. There are many different types of bolts available, each suited for specific applications and uses.
Hex Bolts
Hex bolts, also known as hex cap screws, have a hexagonal head and machine threads for use with a nut or in a tapped hole. They are the most common type of bolt used in machinery and construction. The hex head provides increased surface area to grip with a wrench and apply proper torque.
Carriage Bolts
Carriage bolts have a domed head and a square section under the head that prevents it from turning when the nut is tightened. This makes them ideal for woodworking applications where the square shoulder anchors itself into the wood grain when tightened down. The domed head provides a finished look.
J-Bolts
J-bolts have a J-shaped head that acts as an anchor bolt to provide tie-down points for a variety of applications. They can be embedded in concrete foundations to secure structural columns, used with cable ties to fasten pipes and conduits, or anchored to walls to mount cabinets and shelves.
U-Bolts
U-bolts are shaped like the letter U with threaded ends. They are used to clamp cylindrical objects like pipes, tubes, and rods. Common applications include attaching exhaust systems to vehicles, securing bicycle frames, and anchoring handrails. The curved shape allows tension distribution for a solid clamping force.
Eye Bolts
Eye bolts have a circular ring on the head end to provide an attachment point. They are used with wire rope, chains, and cables to lift, pull, and anchor heavy equipment. Turnbuckles are often attached to eye bolts to tension guy wires and cables.
Lag Screws
Lag screws function as bolts but have a tapered, threaded shank like a wood screw. The threads on a lag screw are coarse to maximize hold in wood. Lag screws are ideal for attaching heavy objects onto wooden studs and beams. Common uses include mounting signs, attaching pergolas, and securing large wooden frames.
Carriage Bolts
- Domed head with square shoulder under the head
- Prevents spinning when tightening the nut
- Commonly used in woodworking applications
Tips for Selecting Bolts
When selecting bolts, consider the materials being joined, required strength, and accessibility for tightening. Consulting an engineer is recommended for structural connections. Use the proper tools and take care not to overtighten and strip threads.
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Choosing the Right Bolt for the Job
With so many types of bolts available, it can be challenging to determine the optimal bolt selection for an application. However, considering factors like strength requirements, materials being joined, environment, and accessibility can help narrow suitable choices.
Strength Requirements
The bolt must be strong enough to handle expected loads without failing. Higher grades offer increased strength but are also more brittle. Common grades are:
- Grade 2 - Basic general use bolt
- Grade 5 - Medium strength steel bolt
- Grade 8 - High strength steel bolt for critical applications
Bolt diameter is also proportional to strength, with larger diameters able to withstand greater forces before shearing or stretching.
Materials Being Joined
Bolt material should match the composition of the materials being joined to minimize galvanic corrosion:
- Stainless steel bolts for stainless or non-ferrous metals
- Zinc plated or galvanized bolts for steel
- Brass bolts for brass fittings or valves
Use self-tapping screws or bolts for plastic, wood, or sheet metal. Concrete anchors are necessary for masonry applications.
Environment
Select bolts that can resist environmental conditions like weather, high temperatures, or corrosive chemicals. Options include:
- Stainless steel - resists corrosion and oxidation
- Galvanized - zinc coating prevents rust
- Brass - withstands high heat and electrical conductivity
Accessibility
The bolt head and nut must be reachable for tools during installation and removal:
- Closed wrenching space - standard hex bolts
- Open wrenching space - eye bolts or hook bolts
- Obstructed access - U-bolts or J-bolts
Key Tips
- Use washers to distribute load and prevent loosening
- Match bolt length to grip length to prevent bottoming out
- Do not exceed torque specifications
- Use thread sealant for bolts in contact with liquids
With knowledge of strength needs, materials, environment, and access, the optimal bolt choice can be made for a connection. Consulting engineers for critical structural joints is advised.
Bolt Grades - Understanding Strength Ratings
Bolts used in structural connections are assigned strength grades that indicate their load carrying capacity. Using the proper bolt grade for an application helps ensure the bolt has adequate strength to transmit forces safely.
Mechanical Properties
Higher bolt grades exhibit greater yield strength, tensile strength, and hardness properties. However, increased strength comes at the expense of reduced ductility and impact toughness. Common bolt strength grades include:
| Grade | Alloy | Tensile Strength |
| Grade 2 | Low carbon steel | 74,000 psi |
| Grade 5 | Medium carbon steel | 120,000 psi |
| Grade 8 | Alloy steel | 150,000 psi |
Markings
Bolt head markings identify the grade. Grade 2 bolts have no markings. Grade 5 bolts are marked with three radial lines. Grade 8 bolts are marked with six radial lines.
Applications
Lower grades like Grade 2 are suitable for light duty connections. Grade 5 provides adequate strength for most general purpose bolted joints. Grade 8 bolts are typically specified for critical structural connections:
- Grade 8 bolts in steel bridge girders, trusses, cranes
- Grade 5 bolts for machinery bases, supports
- Grade 2 bolts for non-structural connections
Safety Factors
Bolted joints are typically designed for the bolt to fail first before the joined members. The higher the bolt grade, the greater the factor of safety against yielding or fracture. Using the appropriate grade is necessary to avoid catastrophic, sudden failures.
Understanding bolt grades helps ensure proper strength specifications for safe structural connections. When in doubt, consult engineering guidance.
How to Measure Bolt Diameter, Length, Thread Pitch
Measuring key bolt dimensions accurately is important for proper identification, specification, and replacing bolts.
Measuring Diameter
Bolt diameter refers to the major diameter or outside edge distance. It can be measured using:
- Calipers - Use the outer jaws to grip bolt head or shank.
- Measuring tape - Wrap around circumference and divide by 3.14 to get diameter.
- Screw gauge - The circular intervals correspond to standard bolt sizes.
Metric bolt diameters are commonly between M3 (3mm) to M64 (64mm). Fractional inch bolts range from 1/4" to 1-1/2" diameter.
Measuring Length
Bolt length is measured from under the head to the end of the shank. Use calipers or a measuring tape aligned with the axis to measure and include the following:
- Shank length
- Head protrusion above shank
- Nut thickness if fixed or integral to shank
Typical bolt lengths start at 15mm or 1/2" and go up based on grip length requirements.
Measuring Thread Pitch
Thread pitch is measured as number of thread crests per unit length. Larger pitches provide greater holding power in soft materials.
- Count threads over 1 inch length using thread pitch gauge.
- Compare threads against gauge to identify pitch.
- Common metric pitches are 1.25, 1.5, 1.75 mm.
- Fractional inch pitches are 12, 13, 16 threads per inch.
Ensure replacement bolts match the original diameter, length, and thread pitch. Using a thread gauge can identify worn bolt specs.
Tips
- Clean threads for accurate thread pitch measurement.
- Handle bolts carefully to prevent wear or damage.
- Consult reference tables for bolt dimensions as needed.
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Using Washers Correctly with Bolts
Washers are vital components in bolted joints that distribute load, reduce friction, and prevent loosening. Using the proper washer type and installation method enhances the performance of the bolted connection.
Washer Types
- Flat washers - Simple round discs that spread load under bolt head/nut face
- Lock washers - Split washer exerts spring force to prevent loosening
- Structural washers - Large diameter for load distribution on thin metals
- Anchor washers - Attaches parts to hollow wall surfaces
When to Use Washers
Washers should be used in the following situations:
- Bolt heads/nuts bear on soft or uneven surfaces
- Joining thin sheet metals prone to tear-out
- Vibration may loosen nuts over time
- Bolts undergo dynamic, fluctuating loads
Washer Installation
Correct washer installation includes:
- Hard smooth washer face against nut/bolt head
- Cupped washer face against joint material
- Split lock washer under nut with prongs facing against nut
- Anchor washers attached to part prior to assembly
Washer Considerations
- Add extra washers if bolt protrudes excessively from nut
- Use oversized washers for large diameter bolts
- Avoid excessive tightening which flattens split lock washer
- Ensure smooth washer movement, not fixed in place
Overall, washers are a simple but critical component in bolted joints. Using the proper washer type and installation method enhances strength, reduces wear, and prevents loosening issues.
Bolt Installation Tips - Tightening, Torque, Preventing Cross-Threading
Proper bolt installation techniques are essential for creating secure, long-lasting bolted joints. Following key tightening sequences, torque recommendations, and steps to prevent cross-threading will result in professional bolted connections.
Tightening Sequence
The order in which bolts are tightened is important to evenly distribute load and prevent warping:
- Finger tighten all bolts first
- Tighten bolts in a crisscross pattern
- Finish with a complete tightening sequence
Applying Torque
- Use a calibrated torque wrench to measure tightening force
- Do not exceed torque specifications for the bolt grade
- Apply torque smoothly without sudden jerking motions
- Confirm final torque with torque wrench after complete tightening
Preventing Cross-Threading
- Align bolt and mating hole perfectly perpendicular
- Start threading bolts by hand until threads catch naturally
- Back out cross-threaded bolts completely and reinsert carefully
- Ensure hole diameters match bolt size specifications
Additional Tips
- Use thread lockers for applications subject to vibration
- Do not reuse stretched or fatigued bolts
- Replace worn bolts - do not re-torque loose bolts
Applying proper techniques for bolt tightening sequence, torque, and cross-threading avoidance will lead to secure bolted joints that stay tightened. Consult engineers regarding critical structural bolting.
Bolt Extraction Techniques - Removing Stuck or Seized Bolts
Removing worn, damaged, or over-torqued bolts can be challenging. However, using the right techniques and tools can help extract stuck bolts efficiently.
Applying Penetrating Oil
Penetrating oils work their way into bolt threads and seep beneath bolt head to break corrosion bonds. Generously apply penetrating oil and allow time to fully wick into the joint prior to attempting removal.
Heating Stuck Bolts
Heating helps break down corrosion on seized bolts. Use a propane torch or induction heater to directly heat stuck bolts until warm to the touch before attempting to loosen.
Shocking with Impact Wrench
Impact wrenches deliver sudden rotational impacts that can shock stuck bolts loose. Use properly-sized impact socket and extensions for optimal torque delivery to rounded, damaged, or recessed bolt heads.
Using Bolt Extractor Tools
- Damaged internal bolt extractors grip inside stripped bolt holes
- Reverse thread extractors backing out around outside of seized bolt
- Center punch can be hammered into stripped hex socket to turn
Drilling Bolts
As a last resort, use a drill to grind away stuck bolt heads. Center punch mark serves as drill guide. May still require specialty pliers or vice grips to back bolt shank out of hole.
Avoid re-using bolts extracted with extreme measures since they are likely fatigued or damaged. Be cautious when applying heat or force during stuck bolt removal.
What is the Use of Amazon Prime for a Regular Buyer of Bolts?
For those who frequently purchase bolts and fasteners for projects, an Amazon Prime membership can provide significant benefits and convenience. Here are some of the key advantages of Prime for regular bolt buyers.
Free Two-Day Shipping
Amazon Prime offers free two-day shipping on hundreds of thousands of items, including most bolts sold directly by Amazon. For those needing bolts quickly, Prime shipping ensures you get your order rapidly with no shipping fees.
Free One-Day and Same-Day Delivery
Prime members in eligible zip codes can get free one-day delivery on over 3 million items. Select areas even offer Prime free same-day delivery on orders over $35. For last minute bolt needs, one-day and same-day shipping ensures you get your order incredibly fast.
Prime Early Access Deals
Amazon Prime members get 30 minute early access to Lightning Deals on Amazon. This includes flash sales on bolts and fasteners, allowing you to take advantage of limited time discounts before non-Prime customers.
Prime Savings on Thousands of Items
Prime members can save up to 20% off on thousands of eligible bolts and fasteners sold directly by Amazon. Savings adds up for regular buyers purchasing frequently.
Amazon Prime Rewards Card
The Amazon Prime Rewards Visa Card provides 5% back on all Amazon purchases for Prime members, including bolts. This rewards cashback can help offset costs for regular bolt buyers.
Overall, an Amazon Prime membership provides significant benefits like free fast shipping, exclusive deals, and purchase rewards that regular bolt buyers can capitalize on.
What Are The Most Common Types Of Bolts And Their Uses?
Bolts are a type of threaded fastener that are used to join two or more components together. There are many different types of bolts, each having different characteristics that make them suitable for use across a wide range of applications. The most common types of bolts include hex bolts, carriage bolts, flange bolts, eye bolts, J-bolts, U-bolts, and T-bolts. Hex bolts are the most commonly used type of bolt and are used in a wide range of applications. Carriage bolts are used to assemble wood and metal components, while flange bolts are used in applications where a wider bearing surface is required. Eye bolts are used to secure cables and wires, while J-bolts are used to anchor walls and support beams. U-bolts are used to secure pipes and tubes, while T-bolts are used in applications where a threaded fastener is required to be inserted into a T-slot.
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What Are The Differences Between J-Bolts And Other Types Of Bolts?
J-bolts are a type of bolt that has a curved profile at one end, while other types of bolts have a straight profile. Here are some differences between J-bolts and other types of bolts:
Differences between J-bolts and anchor bolts:
Differences between J-bolts and L-shaped anchors:
Differences between J-bolts and headed or hooked anchor bolts:
In summary, J-bolts have a curved profile at one end and are typically weaker than other types of bolts such as anchor bolts. Anchor bolts come in various types and are more versatile, while L-shaped anchors have a different shape at the embedded end compared to J-bolts. Headed anchor bolts are generally recommended over hooked anchor bolts due to their higher pullout strength.
What Are The Advantages Of Using J-Bolts Over Other Types Of Bolts?
J-bolts offer several advantages over other types of bolts, including:
- Simple installation: J-bolts can be installed without having to drill a hole into the material it is connecting to, making the installation process simpler and faster.
- Adjustable: J-bolts can be adjusted to fit the specific needs of the application, making them a versatile choice for a wide range of projects.
- Strength and durability: J-bolts are designed to withstand heavy loads without breaking, making them ideal for use in construction projects.
- Versatility: J-bolts can be used for a variety of applications, including anchoring structures such as bridges and buildings, securing machinery and equipment to the ground or walls, and in automotive manufacturing processes and industrial settings such as oil rigs and power plants.
- No concrete failure: J-bolts and L-bolts can pull out before concrete failure occurs, which is a disadvantage. Using a straight bolt with a plate on the end develops a higher bond strength with the concrete, which is an advantage.
In summary, J-bolts offer advantages such as simple installation, adjustability, strength and durability, versatility, and no concrete failure. These advantages make J-bolts a popular choice for a wide range of applications in construction, automotive manufacturing, and industrial settings.
