Types of Nuts and Bolts

This fastener is often used with nuts and washers. Bolts are made in assorted sizes and the diameter of the bolt increases with length. Bolts have heads and threaded parts called shanks. The size of a bolt is associated with the diameter of the shank and the length. Bolt types include:

Carriage Bolts:

• Domed, enlarged head shape
• Designed to keep bolt from pulling through
• Attaches wood to wood or metal to wood

U-Bolts:

• Shaped like the letter “U”, threaded on both ends with nuts
• Supports rope, chain, auto components and pipework

Lag Bolts:

• Also known as lag screws, not used with a nut
• Extremely sturdy, good for bearing heavy loads
• Excellent for flooring and decking

Structural Fasteners:

• Various sizes, from less than a millimeter to over 20 inches long
• Used for various materials, including plastics and composites
• Great replacement for traditional lag and carriage bolts
• Budget-friendly and easy-to-use option for professionals

Eye Bolts:

• Used in rigging, anchoring, pulling, pushing or hoisting applications
• Two types are forged or bent into one piece

Nuts are fasteners with threaded holes that secure to bolts, screws or studs and hold parts together. Once securely fastened, a nut prevents axial movement in connected materials. Types of nuts include:

Cap Nuts:

• Also called an acorn nut, has a domed top
• Caps the exposed ends of shafts, axles and rods

Hex Nuts:

• Six-sided, used for multiple threaded applications
• Finished hex, semi-finished hex, hex flange and slotted hex

Jam Nuts:

• Half as long as standard hex nuts
• Locks in place without clamping to another object

Lock Nuts:

• Also known as nylon lock nuts or prevailing torque nuts
• Used with other nuts to prevent them from loosening

Push Nuts:

• Can be capped or uncapped, installed with a special nut driver
• Removal will destroy fastener

Coupling Nuts:

• Hollow threaded fastener, also called extension nuts
• Joins two male nut threads, driven with a wrench

Speed Nuts:

• Also called a sheet metal nut
• Has two metal pieces that function as one

Square Nuts:

• Threaded nut with four sides
• With various internal platings

T-Nuts:

• Has a flange at the end of a long threaded body
• Often with 3 or 4 prongs to sink into material for better retention

Wing Nuts:

• Threaded nuts with wings on both sides
• Applies and removes with easy manual turning

Bolts and nuts are fabricated from a variety of materials. These options include metals and polymers. Stainless steel offers strength and corrosion resistance. While polymer options have less strength than stainless, they are a good choice for resisting chemicals. The most common materials are:

• Stainless steel
• Alloy steel
• Low carbon steel
• Medium carbon steel
• Titanium
• Polymers, such as nylon

The use of heat treatments and application of various finishes, also known as “plating,” affects the look and performance of nuts and bolts. Finishes provide material stability and protect the fasteners from corrosion and rust. Below are some common heat treatment and finish benefits:

• Zinc coating - Most common, low cost, resists corrosion and rust
• Galvanized - Superior corrosion protection, anti-seize, higher upfront investment
• Stainless – Great for humid environments, strong, ideal for electrical or mechanical uses
• Black – Adds color, provides better grip, deflects light