Gear Applications 251

alloy steel

A steel that contains intentionally added materials or elements. Alloy steels often have improved properties when compared to those of carbon steels.

angle

A shape formed by two lines sharing a common endpoint. Angles can also be formed by two lines that intersect.

apex gap

A groove that runs around the center of a double helical gear. The apex gap separates a double helical gear's two sets of teeth.

automatic transmissions

A complex transmission that does not require the operator to shift gears in order to change the speed and torque of mechanical energy. Automatic transmissions often use planetary gear trains.

axis

An imaginary straight line passing through the center of an object. A round component, such as a gear, typically rotates around its axis, or its centerline of rotation.

backlash

The distance that a gear tooth is able to move without moving its meshing gear and which is required for all gear drives to operate properly. Backlash may also be known as lost motion.

bearings

Friction-reducing devices that allow one moving part to glide past another moving part. Bearings operate using a sliding or rolling mechanism.

belt drive

A mechanical system that consists of a flexible belt and at least two fixed pulleys and is used to transmit motion. Belt drives are low maintenance and do not require lubrication.

bevel gear

A type of conical gear with teeth that are cut at an angle. Bevel gears are often used in angular gear trains.

breakage

The fracture of part or all of a gear tooth. Breakage is often caused by excess loads and gear stress.

bronze

Any copper-based alloy that does not use zinc or nickel as the primary alloying element. Bronzes commonly contain tin, aluminum, or silicon.

carbon steel

A steel that consists of iron and carbon, without any additional materials. Carbon steel may be used to make gears.

cavities

Indentations, or pits, in the surface of a metal. Cavities are often a condition associated with surface fatigue.

centerline of rotation

An imaginary straight line passing through the center of an object. A round component, such as a gear, typically rotates around its centerline of rotation, or its axis.

chain drive

A mechanical system consisting of a chain and sprockets. Chain drives are used to transmit motion from one sprocket to the other.

conical

Cone-shaped, with a cylindrical base and pointed tip. The teeth of some bevel gears are conical.

contaminants

Any damaging foreign substance. Contaminants may cause wear, loss of efficiency, or breakdown in a gear system.

coplanar

Existing or operating in the same plane, or surface. Gear shafts can be coplanar or non-coplanar.

corrosion

The gradual breakdown of a material due to exposure to atmosphere, moisture, or other agents. Some materials are designed to resist corrosion.

crossed-axis helical gears

A set of helical gears with axes that overlap, or cross, one another. Crossed-axis helical gears are used to transmit motion between parallel, non-coplanar gear shafts.

diameter

The distance from one edge of a gear to the opposite edge that passes through the center. The diameter of a gear is the same as its width.

double helical gear

A type of helical gear with two sets of teeth cut at opposing angles and separated by a groove that runs around the center of the gear. Double helical gears are used to provide smoother operation and avoid side loads.

double-enveloping configuration

A worm gear set configuration that uses a worm gear with curved teeth to wrap around an hourglass-shaped worm. Double-enveloping configurations provide the highest amount of tooth contact and can carry the greatest amount of load.

drill presses

A machine tool that is used for a variety of holemaking operations. Drill presses use rotating multi-point cutting tools.

drive gear

A gear that receives energy from a power source, such as an electric motor. Drive gears transmit power to meshing driven gears in order to perform work.

driven gear

A gear that receives motion from the drive gear. Driven gears often transmit power to another meshing gear or an output shaft in order to perform work.

duty cycle

The amount of time that a machine or device continuously operates throughout a 24-hour period. Duty cycle is an important consideration when selecting gears for an application.

efficiency

A measure of the work output of a system versus the total energy input. Efficiency describes the ability of a system to convert a greater amount of supplied energy into intended useful work.

electric motor

A device that converts electricity into mechanical energy or motion. An electric motor is a common power source for a mechanical system.

electric screwdrivers

A type of manual assembly tool that tightens and loosens screws and is powered by electricity. Electric screwdrivers operate quietly and cleanly.

enclosed gear drive

A system of assembled gears that is encased by a housing and transmits mechanical energy from a prime mover to an output device. Enclosed gear drives may also be known as gearboxes.

energy

The ability to do work. Energy, which is never created or destroyed, may be potential or kinetic and may appear as electrical, mechanical, thermal, or chemical energy.

envelop

To wrap around or surround an object. In single- and double-enveloping worm gear configurations, the worm gear's curved teeth partially envelop the worm teeth.

excavators

A type of heavy-duty vehicle most frequently used for moving earth during construction applications. Excavators are sometimes referred to as diggers or mechanical shovels.

extreme pressure additives

Any substance that is added to a material that increases the material's effectiveness as a lubricant under extreme conditions. Extreme pressure additives are often used in heavy-duty industrial applications.

failure

The complete loss of performance. Failure can be the result of gradual wear, incorrect variables, or insufficient lubrication.

ferrous metals

Metals that contain iron. Ferrous metals may be used to make gears.

force

An influence, like a push or a pull, that produces a change in an object's motion or state of rest. Forces have specific directions and magnitudes.

fracture

The breaking of an object into two or more pieces as a result of stress. Fracture can happen without warning or as the result of other forms of wear.

friction

The resistance between the contact surfaces of two objects. Friction generates heat and increases the wear between components.

gear

A round or cylindrical mechanical component with teeth that is used to transmit power. Gears are designed to mesh with one another in order to alter the speed, torque, or direction of mechanical energy.

gear ratio

The relationship between the number of teeth on two meshing gears, or the number of times a drive gear turns in relation to a driven gear. The gear ratio reflects the change in mechanical advantage resulting from the gears.

gear shaft

A cylindrical rod used to support rotating components or transmit rotation in a mechanical system. Gear shafts can be either parallel or at an angle to one another, as well as be either intersecting or non-intersecting.

gear train

A system of gears used to transmit rotary motion from one part of a mechanical system to another. Gear trains are a common method of power transmission.

gearbox

A system of assembled gears that is encased by a housing and transmits transmits mechanical energy from a prime mover to an output device. Gearboxes may also be known as enclosed gear drives.

grade

A classification of industrial lubricants. Grade often describes a lubricant's level of quality.

gradual wear

A type of gear failure that involves the removal of material from the surfaces of the gear teeth. Gradual wear can be reduced through the use of lubricants.

grease

A semi-solid substance composed of oil and a chemical soap or other additive. Grease is commonly used as an industrial lubricant.

hardness

A material's ability to resist penetration, indentation, or scratching. Hardness is an important mechanical property for gear materials.

helical gear

A type of gear with slanted teeth. Helical gears are quieter than spur gears, but they are more expensive and produce side loads.

helix angle

The angle between the axis of a helical gear and an imaginary line that is tangent to the gear tooth. Helix angles can vary in size from 0 to 90 degrees.

herringbone gear

A type of helical gear that has angled teeth in the shape of a letter "V." Herringbone gears are used less frequently than helical and double helical gears.

horizontal

Parallel to the horizon or ground. Horizontal objects span from side-to-side or right-to-left.

horsepower

hp. A unit of power used to describe machine strength. Increased horsepower in a machine results in a greater exertion of force.

housing

A protective cover designed to contain or support a mechanical component. Housings may be used to hold enclosed gear drives.

hypoid bevel gear

A type of bevel gear with angled, curved teeth that transmits motion between non-intersecting shafts. Hypoid bevel gears have teeth that slide together when meshing, which produces less noise but greater friction and heat than other bevel gear types.

idler gear

A gear that keeps the direction of motion consistent between a drive gear and a driven gear. Idler gears rotate in the opposite direction of the drive gear, causing the driven gear to rotate in the same direction as the drive gear.

input shaft

A rotating shaft that receives power from the power source. Input shafts introduce power into mechanical systems.

intersecting

The process of meeting, cutting across, or overlapping. Intersecting lines form the shape of an "X."

involute curve

A curved line that gradually becomes more distant from a center point. An involute curve can be traced by a point on a taut string as it unwinds from a cylinder.

lathes

A machine tool that holds and supports a cylindrical workpiece at one or both ends and rotates it while a single-point cutting tool removes material. Lathes are commonly used to perform turning operations.

left-hand helical gear

A helical gear with teeth that lean to the left when the gear is placed on a flat, horizontal surface. Depending on shaft orientation, helical gears can be combined as two opposite-hand gears or as two matching-hand gears.

linear motion

Motion that takes place along a straight line. Mechanical energy can take the form of rotary or linear motion.

loads

The amount of force or pressure placed on a component or system. Gears must withstand various machine loads during operation.

lockout/tagout

A method of protecting employees from accidental machine startup through proper locking and labeling of machines that are hazardous to nearby employees. Lockout/tagout is an essential practice for safe repair of machines.

lost motion

The distance that a gear tooth is able to move without moving its meshing gear and which is required for all gear drives to operate properly. Lost motion may also be known as backlash.

lubricant

A substance used to reduce friction between two surfaces in relative motion. Common lubricants used in industrial applications include oil and grease.

lubricants

A substance used to reduce friction between two surfaces in relative motion. Common industrial lubricants include oil and grease.

lubrication

The act of applying lubricant to machines, which reduces friction and wear between mechanical components. Lubrication is a common task in preventive maintenance.

lubrication

The act of applying lubricant to machines. Lubrication reduces friction and wear between mechanical components.

machine

To remove material from a workpiece to form an object. Traditional machining methods, such as milling, turning, and drilling, remove metal using cutting tools.

machine tools

A power-driven machine that holds a variety of tools. Machine tools include mills, lathes, and presses.

machines

A device consisting of two or more parts that transform energy into motion. Machines are used to transmit or modify force and motion so as to accomplish some form of useful work.

mechanical advantage

The difference between the applied force and the work accomplished. Mechanical advantage allows machines to perform more work with less effort.

mechanical energy

Energy transmitted through the physical interaction and motion of instruments or tools. Mechanical energy is used to perform work.

mechanical system

A collection of machines functioning together to perform useful work. All modern mechanical systems are based on simple machines.

mesh

The act of interlocking with another object. Gears are designed to mesh with one another in order to transmit mechanical energy.

miter gear set

A type of bevel gear used in pairs with intersecting shafts at 90° angles. In miter gear sets, both the drive gear and driven gear have the same diameter and number of teeth.

motion

A change in an object's original position as a result of a force applied to the object. Motion is typically described in terms of displacement, direction, velocity, acceleration, and time.

nip point

The point where two gears mesh. Nip points can pinch or crush fingers or other body parts.

non-coplanar

Existing or operating in different planes, or surfaces. Gear shafts can be coplanar or non-coplanar.

nonferrous metals

Metals that do not intentionally contain iron. Nonferrous metals may be used to make gears.

non-intersecting

The process of remaining separate and not meeting, cutting across, or overlapping. Non-intersecting lines are parallel to one another.

offset

The distance between the axes of two non-intersecting gear shafts. Offset amounts affect the way in which hypoid gears mesh together.

oil

A slippery fluid commonly used as an industrial lubricant. Industrial oils include both natural and synthetic oils.

open gear systems

A system of assembled gears that is not enclosed within a housing and is exposed to the outside environment. Open gear systems must be lubricated to prevent operational damage.

output shaft

A rotating shaft that receives power from the mechanical system. Output shafts transfer power from a mechanical system to an output source.

overdrive

A combination of gears in an automobile transmission that allows an automobile to sustain speed while using a reduced engine speed. Overdrives usually provide better fuel consumption, less noise, and reduced wear.

parallel

Two lines or axes that are equidistant from each other at all points along their length. Parallel shafts never intersect with one another.

perimeter

The distance around the outside of an object. The perimeter of a circle is also known as its circumference.

personal protective equipment

PPE. Various safety equipment that employees wear or use to prevent injury in the workplace. Common personal protective equipment includes safety glasses, gloves, masks, gowns, and earplugs.

pinion

A circular gear used in a rack and pinion system to produce linear motion. As the pinion turns, the flat rack slides in a linear direction.

pitch

A property used to classify gears. Pitch usually refers to the number of gear teeth in one inch of the gear's pitch diameter, which is also called the diametral pitch.

pitting

A type of gear failure in which cavities, or pits, appear in the surface of a gear. Pitting, or surface fatigue, results from loads that overstress the gear material.

planet carrier

A movable arm on which planet gears are often mounted. Planet carriers ensure that planet gears are properly positioned in relation to the other components in a planetary gear train.

planet gears

One of several outer gears in a planetary gear train that rotates around the sun gear. Planet gears can be mounted on a planet carrier to ensure they are properly positioned.

planetary gear train

A gear train that consists of one or more outer gears rotating around a central gear. Planetary gear trains are also known as epicyclic gear trains.

plastic flow

A gear failure condition in which the gear teeth deform and change shape under pressure. Plastic flow is often due to excess loads and stress.

power source

A device in a mechanical system that generates electricity. Power sources include batteries, electric motors, and generators.

power tools

A tool that is powered by an external source, such as electricity or compressed air. Power tools include electric screwdrivers and drills.

power transmission

The movement of energy from a source to an output device that performs work. Power transmission can be performed in many different mechanical systems, including gear trains, belt drives, and chain drives.

pressure angle

The angle made by the sides of a gear tooth as the sides incline toward the top of the gear. The degree of a gear's pressure angle can affect a gear's strength and resistance to wear.

pump lubrication

A type of gear lubrication system that constantly feeds a liquid lubricant from a reservoir to meshing gears. Pump lubrication systems are sometimes used in enclosed gear drives.

rack

A flat bar with teeth used in a rack and pinion system to produce linear motion. Racks slide in a linear direction as circular pinions turn against them.

rack and pinion

A gear pair that is used to convert rotary motion into linear motion. A rack and pinion consists of a circular gear, or pinion, that meshes with a flat-toothed bar, or rack.

right angle

An angle that is always 90 degrees. A right angle is formed when two lines that are perpendicular to one another intersect.

right-hand helical gear

A helical gear with teeth that lean to the right when the gear is placed on a flat, horizontal surface. Depending on shaft orientation, helical gears can be combined as two opposite-hand gears or as two matching-hand gears.

ring gear

A circular gear with teeth that mesh with the teeth of planet gears in a planetary gear train. Ring gears are internal gears because their teeth face inward rather than outward.

rotary motion

Spinning or turning motion that takes place around an axis, without a change in linear position. Mechanical energy can take the form of rotary or linear motion.

single-enveloping configuration

A worm gear set configuration that uses a gear with curved teeth to wrap around part of the worm. Single-enveloping configurations provide more contact between the worm and worm gear teeth and can carry heavier loads.

slip

A condition that occurs in flat belt drives. Slip is when the load causes the belt to slide out of proper position on the pulley.

spalling

A type of gear failure in which cracks at or near the surface of a gear tooth progress into the tooth body. Spalling often leads to gear tooth fracture.

speed

The rate at which an object travels a given distance. Speed is used to measure both linear and rotational movement.

speed increaser

A gear train that increases the speed of mechanical energy while decreasing the torque. Speed increasers are used in some automobile transmissions.

speed increasers

A gear drive used to increase the speed of mechanical energy while decreasing the torque. Speed increasers are used in some automobile transmissions.

speed reducer

A gear train that reduces the speed of mechanical energy while increasing the torque. Speed reducers often use gearboxes with worm gears and worms.

speed reducers

A gear drive used to reduce the speed of mechanical energy while increasing the torque. Speed reducers are often gearboxes that use worm gears and worms.

spiral angle

The angle at which spiral bevel gear teeth are set from the gear shaft axis. The spiral angle of most bevel gears is 35 degrees.

spiral bevel gear

A type of bevel gear with conical and curved teeth, designed for smooth operation. Spiral bevel gear teeth have a spiral angle.

splash lubrication

A type of gear lubrication system in which the teeth of a gear dips into a tray of lubricant as the gear rotates and then transfers the lubricant to the meshing gear as it rotates. Splash lubrication systems are sometimes used in enclosed gear drives.

spray lubrication

A type of gear lubrication system that provides a constant mist of lubricant to meshing gears. Spray lubrication systems are sometimes used in enclosed gear drives.

spur gear

A type of gear that has straight, flat-topped teeth set parallel to the shaft. Spur gears are the most common type of gears used in industry.

straight bevel gear

A basic bevel gear, which has tapered teeth that are widest at their outer part. Straight bevel gears are cost-effective when transmitting power between shafts at right angles.

straight cylindrical configuration

A worm gear set configuration that uses a cylindrical worm to mesh with a worm gear. Straight cylindrical configurations offer high speed reduction ratios but can be used only with light loads.

sun gear

The central gear in a planetary gear train. The planet gears rotate around the sun gear.

surface fatigue

A type of gear failure in which cavities, or pits, appear in the surface of a gear. Surface fatigue, or pitting, results from loads that overstress the gear material.

tapered

Gradually decreasing in size from one end of the object to the other. Tapered gear teeth are usually widest at their outer part.

threads

A raised, helical ridge around the exterior of a cylindrically shaped object. A worm's threads are designed to mesh with a worm gear's teeth.

thrust bearing

A type of bearing designed to reduce friction by carrying thrust, or axial, loads. Thrust bearings can be either plain or anti-friction bearings.

thrust load

A force that attempts to shift a component off its axis of rotation. Thrust loads occur when gear teeth mesh together at an angle.

torque

A force that produces rotation. Torque is measured in pound-feet (lb-ft) in the English system and newton-meters (Nm) in the metric system.

toughness

A material's ability to absorb energy without breaking or fracturing. Toughness is a key property that determines a material's ability to withstand a sudden stress.

transmissions

A machine that uses a combination of gears and other mechanical components to change the speed or torque of mechanical energy. Transmissions are frequently used in motor vehicles.

vibration

A rapid continued, repeated motion in a machine or other structures. Vibration can negatively affect mechanical operations.

wear

The erosion of material as a result of friction. Wear typically is caused by two or more objects rubbing or sliding against each other.

work

The result of a force applied to an object and the distance through which the force is applied. In an equation, work is force multiplied by distance.

worm

A cylindrical, screw-shaped shaft that is used with a worm gear to transmit motion. Worms are usually the drive gears in worm gear sets.

worm gear

A gear with teeth that mesh with the screw-like threads of a shaft, called a worm, to transmit motion. Worm gears are usually the driven gears in worm gear sets.

worm gear drives

A gear drive consisting of a long, cylindrical device with a spiraling groove that intersects with the teeth of a wheel-like gear. A worm gear drive is used to transmit motion between non-intersecting perpendicular shafts.

worm gear set

A worm gear used in combination with a worm. Worm gear sets are used to transmit power between non-intersecting shafts at right angles to one another.

wrap point

An exposed rotating shaft. Wrap points have the potential to become caught on clothing, pulling a person toward the machinery and potentially causing injury.

zero bevel gear

A type of bevel gear with curved teeth and a 0° spiral angle. Zero bevel gears provide smooth and quiet operation, but they produce thrust loads.