16 Different Types of Bolts and Why You Need Them
When your equipment goes down or a project hits a snag, knowing which types of bolts to reach for can get you back on track quickly. From hex heads that handle high torque to specialty bolts built for extreme conditions, there are many different types of bolts, and all of them play an important role in keeping industries like mining, construction, automotive, and manufacturing running.
Here's everything you need to know about different types of bolts, and how to choose the ones that'll get things connected and stay that way under pressure.
What Is a Bolt?
A bolt is a threaded fastener that passes through holes in assembled parts and secures them with a nut on the opposite end. Unlike screws, which thread directly into materials, bolts work with nuts to create removable joints that can handle significant loads and stress. The threaded shaft provides the holding power, and the head gives you the leverage to tighten the connection to specification.
At D&T Enterprises, we stock the bolts that keep critical operations running, from standard hex heads to specialty fasteners that handle whatever your job throws at them.
16 Different Types of Bolts and What They're Used For
1. Hex Bolts
Popular industries: Mining, cranes & rigging, construction, automotive
Hex bolts are the workhorses of heavy-duty fastening, featuring a six-sided head that provides maximum grip for wrenches and sockets. The hexagonal design lets you apply torque without the head stripping or rounding out, which is important when you're dealing with high-stress applications.
You'll find hex bolts in everything from mining equipment to crane work. They come partially or fully threaded and work with nuts and washers to create secure, removable connections.
You also might be interested in learning about hex cap screws.
2. Carriage Bolts
Popular industries: Construction, municipal & utility services, heavy equipment repair
Carriage bolts have a smooth, rounded head with a square neck that prevents the bolt from turning once it's seated. This design makes them great for applications where you only have access to one side of the connection. The square section locks into the material or a square hole, letting you tighten from the nut side alone.
These bolts excel in wood construction, dock building, and situations where you're joining materials of different thicknesses. The smooth head sits flush and won't snag equipment or tear clothing, which makes carriage bolts a smart choice for railings and outdoor structures that see regular use.
3. Structural Bolts
Popular industries: Construction, oil & gas
Structural bolts are engineered for the demanding world of steel construction and heavy framework. These high-strength fasteners meet strict specifications (typically ASTM A325 or A490) and can handle the massive loads and dynamic forces found in bridges, buildings, and industrial structures.
4. Tap Bolts
Popular industries: Manufacturing, automotive
Tap bolts thread directly into pre-tapped holes without needing nuts, which makes them a solid option for applications where space is tight or access to the back side is limited. These fully-threaded fasteners create strong connections by engaging with threads cut into the base material, whether that's steel, cast iron, or other metals.
Common in machinery maintenance and equipment repair, tap bolts simplify assembly and reduce the number of components you need to manage. They're especially useful in automotive work and other projects where you're attaching components to thick materials that can accommodate threaded holes.
5. Lag Screws
Popular industries: Construction, heavy equipment repair
Lag screws, or lag bolts, give you the threading action of a screw and the strength of a bolt, featuring a hex head and aggressive threads that can bite into wood and other materials. They're built to handle substantial loads in timber construction and heavy-duty wood applications.
Lag screws eliminate the need for pre-drilling in many applications and create strong, permanent connections that can support a lot of weight.
6. Flange Screws
Popular industries: Manufacturing & industrial plants, automotive
Flange screws have a built-in washer-like flange beneath the head that distributes load across a wider area. This eliminates the need for separate washers in many applications.
An integrated design like this speeds up assembly and ensures consistent load distribution, which makes flange screws popular in automotive, HVAC, and sheet metal work where you're joining thinner materials that could be damaged by concentrated pressure.
7. Plow Bolts
Popular industries: Heavy equipment repair, construction, municipal & utility services
Plow bolts feature smooth, countersunk heads that sit flush with surfaces. They won't snag on soil, debris, or materials, which is essential for agricultural equipment and construction machinery where protruding heads cause problems.
These types of bolts are built for field work and heavy equipment operations. The flat head design reduces drag and prevents soil buildup, and it's also great at handling constant vibration and impact from ground contact.
8. Step Bolts
Popular industries: Mining, cranes & rigging
Step bolts create safe footholds on towers, tanks, and vertical structures. One end threads into the mounting surface. The other extends out to form a step or handhold. These types of bolts are critical for mining operations and crane maintenance where workers need secure access to elevated equipment.
9. Elevator Bolts
Popular industries: Mining, manufacturing & industrial plants
Large, flat heads with square necks make elevator bolts a great choice for material handling and conveyor systems. The wide head spreads loads evenly, and the square neck prevents rotation during tightening. These types of bolts are common in mining operations and manufacturing facilities.
10. Timber Bolts
Popular industries: Construction, municipal & utility services
These heavy-duty fasteners are built specifically for structural wood connections. Their deep, aggressive threads grip wood fibers, and they can handle big loads in timber framing and construction work. Timber bolts are essential for construction projects and municipal infrastructure where wooden structures need permanent, reliable connections.
11. Square Head Bolts
Popular industries: Construction, heavy equipment repair, automotive maintenance
Square head bolts use a four-sided head instead of hex. The square shape gives you a solid grip with wrenches and prevents the bolt from turning in square holes. These bolts handle high torque without rounding out.
You'll see them in older construction equipment and restoration projects where square heads were the standard. They're also useful when you need the bolt head to sit in a square recess or when working with antique machinery that was originally built with square head hardware.
12. Anchor Bolts
Popular industries: Construction, oil & gas
Anchor bolts secure structures and equipment to concrete foundations. They're either cast in place during concrete pours or installed into drilled holes with epoxy or mechanical anchors. These bolts transfer loads from structures into solid concrete.
They're essential for mounting heavy machinery, securing structural steel columns, and anchoring equipment that can't move. In oil and gas facilities, anchor bolts keep critical equipment properly positioned even with vibration and thermal expansion.
13. Eye Bolts
Popular industries: Cranes & rigging, manufacturing
Eye bolts have a loop or "eye" instead of a standard head, designed for lifting, pulling, and securing loads with cables or chains. The eye provides a strong attachment point that won't slip or come loose under load.
It's an important bolt for rigging operations and material handling. Crane crews use them as lifting points, and manufacturing plants rely on them for securing equipment and creating tie-down points. Always check load ratings. Eye bolts have specific limits for straight pulls versus angled loads.
14. Toggle Bolts
Popular industries: Construction, manufacturing, HVAC installation
Toggle bolts work in hollow walls where you can't reach the back side. Spring-loaded wings collapse to fit through holes, then expand behind the wall to distribute loads across a wider area.
These types of bolts are useful for mounting equipment to metal panels or drywall where there's no solid backing. In manufacturing facilities, they're handy for securing lighter equipment to hollow structural members or thin wall sections.
15. Hanger Bolts
Popular industries: Construction, manufacturing
Hanger bolts have wood screw threads on one end and machine threads on the other. The wood end screws into lumber while the machine end accepts nuts and washers for attaching hardware.
They're perfect for connecting metal brackets to wooden structures or hanging equipment from overhead beams. Construction crews use them for mounting electrical boxes and HVAC equipment to wooden framework.
16. Stove Bolts
Popular industries: Manufacturing, automotive
Stove bolts are small-diameter fasteners with slotted or Phillips heads, designed for light-duty applications. Despite the name, they're used far beyond stoves and anywhere you need a clean, finished appearance with moderate holding power.
These types of bolts are common in equipment panels, electrical enclosures, and light manufacturing. The small head sits nearly flush and won't snag on clothing or equipment.
Want to see what bolts we stock at D&T? Get our product guide:
What Is the Strongest Kind of Bolt?
The strongest bolts are Grade 8 and Grade 9 in standard size, as well as Grade 10.9 or Grade 12.9 (metric) hex head cap screws, which can handle tensile strengths from 150,000 psi up to 180,000 psi. For structural applications, A490 bolts represent the top tier with tensile strengths around 150,000-170,000 psi.
Strength isn't just about the grade, though. The right bolt for your application depends on the specific loads, environmental conditions, and safety requirements you're dealing with. A Grade 5 bolt in the right application can outperform a Grade 8 bolt used incorrectly.
Get High-Quality Bolts at D&T Enterprises
At D&T, we keep extensive stock of hex head cap screws, structural bolts, and specialty fasteners in the grades and materials that heavy industries need. Whether you work in mining, construction, crane operations, heavy manufacturing, or another industry, we have what keeps your operations running.
With over 10,000 products on hand and the ability to source hard-to-find specs, we make it easy to get exactly what you need.
Ready to get the right bolts for your job? See all the products we stock, or contact D&T today for expert advice and competitive pricing on the fasteners that hold your operation together.
