Overview of Threaded Fasteners 117

This class summarizes the various types of threaded fasteners used in assemblies and describes their common applications.

Class Details

Class Name:
Overview of Threaded Fasteners 117
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Class Outline

  • Objectives
  • What Is a Mechanical Fastener?
  • Threaded and Non-Threaded Fasteners
  • Types of Threaded Fasteners
  • Bolts
  • Parts of a Bolt
  • Types of Bolts
  • Types of Specialized Bolts
  • Screws
  • Types of Screws
  • Nuts
  • Cotter Pins and Castle Nuts
  • Locking Nuts
  • Washers
  • Types of Washers
  • Summary


  • Describe the advantages of mechanical fasteners.
  • Identify the major types of mechanical fasteners.
  • Identify the most common types of threaded fasteners.
  • Describe bolts.
  • Identify the parts of a bolt.
  • Identify common types of bolts.
  • Identify bolts for special applications.
  • Describe screws.
  • Identify common types of screws.
  • Describe nuts.
  • Describe castle nuts.
  • Identify locking nuts and components for special applications.
  • Describe washers.
  • Identify common types of washers.


  • Job Planning, Benchwork, & Layout I
  • Job Planning, Benchwork, and Layout-FastTrack
  • Metalforming I


Vocabulary Term Definition
assemble To join or fit together.
bearing surface The circular underside of the bolt head that makes contact with the part.
blind hole A hole that does not pass through a component and has only one opening.
bolt An externally threaded, cylindrical fastener with a head at one end and a threaded blunt end at the other. Bolts are designed to fit into non-threaded holes to join parts and are assembled with a nut.
bolt head The enlarged shape on one end of a bolt. The type of bolt head determines the type of tool used to tighten it.
carriage bolt A type of bolt with a round head and a square neck underneath that prevents the bolt from turning while the nut is tightened.
castle nut A type of nut with rounded extensions projecting past the nut's opening. A cotter pin is inserted through a hole in the bolt and bent around the castle nut's projections to lock the nut in place.
chamfered Angled or beveled along an edge.
corrosion resistance The ability of a material to resist chemical destruction from an environment. Corrosion resistance is the most important physical property for fasteners.
cotter pin A pin with two ends originally positioned together that are fitted through a hole and then bent backwards to lock the pin and other components in place.
disassemble To take apart by design, often with the intention of reassembly.
dome head bolt A type of bolt with a rounded head above the head's flats that is made of wear-resistant material. Dome head bolts are used in industrial and farming equipment.
driving recess The shape on the top of a fastener head designed to accept a matching driving tool.
external thread A thread that spirals around the exterior surface of a cylindical component.
flat One of the level surfaces on the head of a fastener that forms a side.
flat metal lock A flat, thin metal component that is inserted with a nut over a bolt. The metal lock is bent to contact the nut and prevent loosening.
flat washer A common type of round washer that is flat with a hole in the center. Also called a plain washer.
friction A force that resists motion between two components that are in contact with each other.
grip length The length of the unthreaded section of the bolt shank.
hex bolt A bolt with a six-sided head.
hex key A small hexagonal-shaped wrench that is used to fasten socket head cap screws.
hexagonal Having six sides.
impact tool An air-powered tool that uses a discontinuous-drive clutch to produce torque. Impact wrenches are often used to tighten lug nuts on cars when changing a tire.
interference An amount of overlap between two objects. Locking nuts have various features designed to add interference and prevent loosening.
internal thread A thread that spirals around the interior surface of a hole.
jam nut A thin nut that is assembled with a regular nut to lock both nuts in place. The jam nut provides extra resistance that helps prevent loosening.
load The overall force that is applied to a material or structure. A fastener that supports the weight of an object is withstanding a load.
locking nut Any type of nut that is designed with features for providing extra security against unintended loosening of the nut and bolt.
locking washer Any type of washer designed with a feature that adds tension and helps prevent loosening of the joint.
machine screw A common type of screw with a blunt end that is assembled into a threaded hole.
mechanical fastener A device that holds two or more objects together. A fastener can be a button or a zipper as well as a bolt or a screw.
non-threaded fastener A type of fastener that does not contain threads. Common types of non-threaded fasteners include pins, retaining rings, and rivets.
nut A small device with internal threads that is fitted onto a bolt to join parts. Most nuts are square or hexagonal.
pin A thin, often straight, cylindrical non-threaded fastener used to secure the position of two or more machine parts.
plain washer A common type of round washer that is flat with a hole in the center. Also called a flat washer.
plow bolt A type of bolt with a flat, circular top and a four-sided shape underneath.
point The extreme end of the threaded portion of a bolt.
retaining ring A flat, circular, non-threaded fastener with a hollow center and an open section. Retaining rings provide a shoulder and can be inserted onto a shaft or inside a hole with an internal groove.
rivet A type of non-threaded fastener that consists of a shank and a head made of deformable material. Rivets are inserted through holes, and the shank is formed into a matching head on the other side of the part.
screw An externally threaded, cylindrical fastener with a head and a threaded flat or pointed end opposite the head. Screws are designed either to fit into a threaded hole or form threads into material.
sealant A substance applied to a joint that dries and hardens to lock components in place.
set screw A type of screw with a rounded or cone-shaped end designed to fit into a matching recess. A set screw is typically used to lock a component onto a shaft.
shank The cylindrical length of the bolt that extends from the underside of the head to the point or end.
socket A device that covers a nut or bolt completely for tightening or loosening. Sockets attach to various devices that are used to tighten the bolt or nut.
socket head cap screw A type of bolt with a recess inside the bolt's head. Socket head cap screws require assembly with a hex key or a hex bit driven by an impact tool.
split-ring washer A type of locking washer with a split section that is intentionally bent out of shape. As a nut is tightened, the split-ring washer is forced back into a flat shape, which adds tension to the joint.
square-head bolt A bolt with a four-sided head.
strength-to-weight ratio The relationship between a material's strength and its weight. Materials that are light but also very strong have a high strength-to-weight ratio.
structural bolt A large, heavy-duty hex bolt used for structural applications in buildings and bridges.
stud An externally threaded fastener that is threaded at both ends. Unlike bolts, studs do not have a head.
tensile strength The ability of a material to resist forces that attempt to pull apart or stretch it.
tension A pulling force that is directed away from the object and attempts to stretch or elongate the object.
T-head bolt A type of bolt with a T-shaped head that matches T-slots in a machine table. T-head bolts are used for holding parts on a machine table.
thread A raised, helical rib or ridge around the interior or exterior of a cylindrically shaped object. Threads are found on screws, nuts, and bolts and are used to fit parts or provide motion.
thread length The length of the threaded section of the bolt shank.
threaded fastener A type of fastener that contains threads. Bolts, screws, and nuts are examples of threaded fasteners and are the most common type of fastener.
tolerance The unwanted but acceptable deviation from a desired dimension. Increasingly accurate dimensions require tighter tolerances.
torque The amount of force applied to tighten a bolt, screw, or nut.
T-slot A T-shaped opening that runs the length of a machine table. T-slots enable machinists to clamp vises and other workholding components onto the table.
twelve-point bolt A bolt with a double-hexagonal, or 12-sided bolt head. Twelve-point bolts are common in the aircraft industry.
washer A flat disc with a hole through the center that is often used with threaded fasteners to ensure tightness of the joint.
washer face The completely flat side of a nut that is intended to contact the surface of a washer.
wrench A type of hand tool that tightens and turns bolts and nuts. Wrenches contain fixed or moving jaws or a round attachment that grips the nuts or bolts.