Mechanical Engineering & Machinery

The physical building blocks of machinery, including bearings, seals, and fasteners.

• Antibacklashalso anti-backlash
  Designed to eliminate the clearance or play between mating mechanical parts like gears or lead screws.
• Ball bearingalso deep groove bearing
  A mechanical bearing that reduces rotational friction by capturing spherical rolling elements between two grooved rings.
• Ballracealso race, bearing race
  The grooved track or ring that guides the rolling balls within a ball bearing assembly.
• Bearing
  A machine element that constrains relative motion to a desired direction and reduces friction between moving parts.
• Belt trackalso continuous track, rubber track
  A continuous flexible band driven by wheels to propel a vehicle over soft or uneven ground.
• Blankalso slug
  A piece of raw material pre-cut to a rough size and shape before final machining or forming.
• Bootalso bellows, dust boot
  A flexible protective cover that seals a moving joint or shaft against contamination.
• Bossalso mounting pad
  A raised, reinforced feature on a part used for mounting, locating, or assembling other components.
• Bufferalso bumper, bump stop
  A resilient component designed to absorb impact forces and prevent metal-to-metal contact.
• Bulkhead
  A rigid partition used to separate compartments or mount feed-through connectors.
• Bushing
  A cylindrical sleeve used as a plain bearing to reduce friction and wear inside a hole.
• Catheadalso capstan head, winch head
  A spool-shaped winch head used to pull ropes or cables by wrapping them around its rotating surface.
• Crankwebalso web
  The solid radial segment of a crankshaft that connects the main journal to the crankpin.
• Crosshead
  A sliding block that connects a piston rod to a connecting rod, absorbing lateral forces.
• Diaphragm
  A flexible membrane that seals two chambers while allowing pressure to transfer or a rod to actuate.
• Elliptic springalso full-elliptic spring
  A suspension component made of two opposing semi-circular leaf springs joined at their ends.
• Feathered
  Machined or ground down to a very fine, tapered edge.
• Finger-piecealso thumb-piece, tab
  A small mechanical lever or tab designed for manual actuation by a single digit.
• Flywheel
  A heavy rotating wheel that stores kinetic energy to smooth out power delivery in a machine.
• Gasket
  A compressible seal used to fill the gap between two mating surfaces.
• Glandalso stuffing box, packing gland
  A housing and compression collar that forces packing material tightly against a moving shaft.
• Guidealso guideway
  A mechanical component that forces a moving part to travel along a specific linear or curved path.
• Handwheel
  A manually turned wheel used to adjust a mechanism or operate a valve.
• Inlead
  A dedicated channel or conduit allows wires and fluids to pass safely into a sealed enclosure.
• Jibhead
  The outermost structural end of a crane arm supports the lifting tackle.
• Journal
  The specific cylindrical portion of a shaft rests and rotates within a bearing.
• Journal box
  A protective housing that encloses a rotating shaft end and its bearing to retain lubricant and block debris.
• Keyalso Woodruff key, parallel key
  A solid metal block locks a rotating shaft to a hub to transmit torque.
• Keyed
  A mechanical connection uses a locking insert to prevent relative rotation between a shaft and a hub.
• Keyway
  A longitudinal slot cut into a shaft or hub to receive a key.
• Mushroom head
  A fastener or component top that features a wide, domed profile.
• O-ringalso toric joint
  A circular elastomer gasket with a round cross-section used to seal fluid or gas connections.
• OD
  The outside diameter of a cylindrical object like a pipe, tube, or shaft. Shop talk
• Pedestalalso pillow block, plummer block
  A sturdy mounting base or housing that supports a rotating shaft.
• Quill
  A hollow rotating shaft that houses another shaft or spindle inside it.
• Radial shaft sealalso lip seal, oil seal
  A flexible ring that presses against a rotating shaft to retain lubricant and exclude dirt.
• Rotor
  The rotating inner component of a mechanical or electrical machine.
• Screenalso mesh, strainer
  A porous barrier made of woven wire or perforated metal used to filter fluids and block large debris.
• Seatingalso seat, mounting
  The machined surface or housing where a component rests and transfers its load.
• Shock absorberalso damper, shock
  A mechanical or hydraulic device designed to damp sudden impulses and dissipate kinetic energy.
• Side playalso axial clearance, end play
  The allowable lateral movement or clearance between assembled mechanical parts.
• Sprocketalso sprocket wheel
  A profiled wheel with teeth that mesh with a chain, track, or perforated material.
• Stabilizeralso anti-roll bar, sway bar
  A mechanical linkage or structural element used to resist unwanted motion or roll.
• Strapalso band, retaining strap
  A flat, narrow band of metal or flexible material used to bind, secure, or connect components.
• Swivel
  A coupling that allows connected parts to rotate independently.

The assemblies of levers, gears, and cams that translate and multiply mechanical motion.

• Alligatoralso alligator shear, crocodile shear
  A heavy-duty mechanical shear or crusher featuring a hinged, lever-actuated upper jaw. Shop talk
• Beamalso walking beam
  A heavy oscillating lever used in early engines to transmit motion from a vertical piston to a rotating crank.
• Bellcrankalso bell crank
  A pivoting lever bent at an angle to change the direction of applied force or motion.
• Boat liftalso shiplift
  A mechanical elevator system that transports vessels vertically between different water elevations.
• Braked
  Equipped with a braking mechanism to control or stop motion.
• Cambox
  An enclosed mechanical housing that contains and lubricates a camshaft assembly.
• Cardan shaft
  A driveshaft equipped with universal joints to transmit torque at variable angles.
• Chain drive
  A power transmission system that uses a roller chain engaging with toothed sprockets.
• Chain-driven
  Describes a mechanism that transmits power using an endless loop of linked metal.
• Clutch
  A mechanical device that engages and disengages power transmission between a driving shaft and a driven shaft.
• Crank axle
  A driven axle featuring integrated cranks to convert reciprocating motion into rotation.
• Deadbandalso dead zone, neutral zone
  A range of input movement or signal that produces no output response in a mechanical or control system.
• Differential steeringalso skid steering
  A steering method that turns a vehicle by driving the wheels or tracks on each side at different speeds.
• Escapement
  A mechanical linkage that controls the release of stored energy in discrete, regular steps.
• Flyweightalso centrifugal weight
  A small mass in a rotating mechanism that moves outward under centrifugal force to actuate a control.
• Footwheelalso treadle wheel
  A wheel or treadle mechanism driven by the operator's foot to power a machine. Shop talk
• Freewheel
  To continue rotating independently after the driving force stops or disengages.
• Geneva mechanismalso Maltese cross mechanism
  A gear arrangement that converts continuous rotation into intermittent, stepped motion.
• Geneva wheelalso Maltese cross mechanism, Geneva stop
  A mechanical linkage that translates a continuous rotation into intermittent rotary motion.
• Handbrakealso parking brake, emergency brake
  A manually operated lever or crank mechanism used to engage a friction brake.
• Inclined planealso ramp
  A flat surface tilted at an angle reduces the force required to raise a load.
• Knife-edgealso knife-edge bearing, knife-edge pivot
  A sharp, hardened contact point used as a low-friction fulcrum.
• Lashalso backlash, play
  The mechanical clearance or lost motion between moving parts. Shop talk
• Lever
  A rigid bar resting on a pivot, used to multiply mechanical force.
• Luff
  To raise or lower the angle of a crane jib to change the working radius of the load.
• Motionalso motion work
  The collective assembly of moving parts in a complex mechanism. Shop talk
• Peritrochium
  An older term for a wheel fixed to an axle to form a simple lifting machine.
• Planet wheelalso planet gear, planetary gear
  A gear that revolves around a central sun gear within an epicyclic gear train.
• Polyspast
  A historic lifting machine or block-and-tackle system equipped with multiple pulleys.
• Pushrod
  A rigid metal shaft that transmits linear motion from a cam to a valve or lever.
• Rackalso gear rack
  A straight bar with gear teeth cut into one face to translate rotational motion into linear motion.
• Reduceralso gear reducer, speed reducer
  A mechanical or hydraulic device that decreases input speed or pressure to increase output torque or displacement.
• Roddingalso linkage
  A network or assembly of rigid rods used to transmit mechanical motion across a distance.
• Self-clampalso self-locking, self-tightening
  Describing a mechanism that uses the applied load or motion to increase its own gripping force.
• Tackle blockalso pulley block, snatch block
  A pulley assembly enclosed in a shell used with ropes to lift heavy loads.
• Yokealso clevis
  A U-shaped mechanical component used to link, support, or transmit motion between two other parts.

Systems that convert pressure and combustion into work using pumps, cylinders, and valves.

• Accumulatoralso hydro-pneumatic accumulator
  A pressure vessel that stores hydraulic fluid under pressure to release energy on demand.
• Air cellalso prechamber, Lanova cell
  A small secondary combustion chamber in some indirect injection diesel engines.
• Air hosealso pneumatic line
  A flexible tube designed to carry compressed air from a compressor to pneumatic tools or actuators.
• Bleed holealso bleed port, vent hole
  A small, intentional opening designed to equalize pressure or vent trapped fluids from a system.
• Breatheralso breather valve, vent
  A vent that allows air to flow in and out of an enclosed space to equalize pressure.
• Bucketalso turbine blade
  A curved blade or cup on the periphery of a turbine rotor.
• Bull pump
  A historic single-acting pumping engine with the steam cylinder directly over the pump.
• Cataract
  A historic hydraulic governor used to regulate the timing of early steam engines.
• Cylinder
  The tubular chamber in which a piston travels to compress a fluid or convert fluid pressure into mechanical work.
• Double-acting
  Capable of applying force in two opposing directions.
• Draught enginealso draft engine
  An early stationary engine built specifically for pumping water or hauling heavy loads.
• Dry heater
  A pneumatic engine design that burns fuel with compressed air or oxygen without injecting water for cooling.
• Ejectoralso jet pump, eductor
  A fluid pump that uses a high-pressure jet to entrain and move a secondary fluid.
• Electrogyro
  An energy storage system that uses an electric motor to spin a heavy flywheel.
• Flow meteralso flowmeter
  An instrument that measures the volume or mass of a fluid moving through a pipe per unit of time.
• Four-way cockalso four-way valve
  A rotary valve with four ports used to direct fluid flow between different paths.
• H-piece
  A pipe fitting or pump manifold shaped like the letter H, used to route fluid flow.
• Headalso cylinder head, pressure head
  The static pressure of a fluid expressed as the height of a liquid column, or a cylinder cover.
• Hydraulic radius
  The ratio of a fluid channel's cross-sectional area to its wetted perimeter.
• Idlealso idle speed
  The baseline operating speed of an engine when it is running but disconnected from a load.
• Ignition
  The system or event that initiates combustion within an engine cylinder.
• Low-powered
  Having a relatively small output of mechanical or electrical energy.
• Manifold
  A pipe or chamber with multiple openings that distributes or gathers fluid.
• Overshot
  Describing a waterwheel driven by water falling onto its upper paddles or buckets.
• Piston
  A sliding cylinder that moves back and forth inside a hollow tube to compress fluid or transmit force.
• Poppet valvealso mushroom valve
  A directional valve consisting of a flat disk on a stem that lifts away from its seat to permit flow.
• Pump valve
  A mechanical barrier that directs or restricts fluid flow within a pumping system.
• RICE
  The abbreviation for reciprocating internal combustion engine.
• Scrollalso volute, scroll casing
  A spiral-shaped casing or fluid passage surrounding a turbine or compressor rotor.
• Shaft horsepoweralso SHP
  The actual mechanical power delivered to a rotating output shaft.
• Snifting valvealso snifter valve
  An automatic relief valve used to vent trapped air from a steam cylinder or pump.
• Trunk piston
  A long, hollow piston that connects directly to the connecting rod.
• Two-strokealso two-cycle
  Describing an engine that completes a power cycle in just one upward and one downward piston movement.
• Unportalso Unporting
  To expose an intake or drain opening to air instead of fluid.
• Valve gearalso valvetrain
  The mechanical linkage that controls the timing and duration of fluid entering and exiting a cylinder.
• Wet heater
  A torpedo propulsion engine that injects water into its combustion chamber to generate steam.

The physics of forces, mass, and motion acting upon physical bodies and structures.

• Accelerated motion
  A state where an object's velocity changes continually over time.
• Anharmonicity
  The degree to which an oscillating system deviates from simple harmonic motion.
• Antiplanealso antiplane shear, longitudinal shear
  Describing a deformation state where all displacement occurs perpendicular to a two-dimensional plane of interest.
• Bottomalso bottom out
  A moving component reaches the physical end of its travel limit.
• Compliance
  The inverse of stiffness, representing how much a structure deforms under a given load.
• Continuum mechanics
  The analysis of the kinematics and mechanical behavior of materials modeled as a continuous mass.
• Critical taper
  The equilibrium angle at which a wedge of granular material can be pushed without internally deforming.
• Damping
  The dissipation of energy in a vibrating system to reduce the amplitude of oscillations over time.
• Dynamicist
  An engineer or physicist who specializes in the study of bodies in motion and the forces that act upon them.
• Flexiblealso compliant, elastic
  Capable of undergoing significant elastic deformation under load without failing.
• Fluid mechanics
  The study of how liquids and gases behave at rest and in motion under various forces.
• Flutteralso aeroelastic flutter
  A dangerous, self-feeding vibration in a flexible structure exposed to aerodynamic forces.
• Flux
  The rate at which a fluid, particle, or energy crosses a specific surface area.
• Force pairalso action-reaction pair
  Two forces of equal magnitude acting in opposite directions on interacting bodies.
• Form factoralso shape factor
  A dimensionless ratio used to describe the shape of an object or its stress distribution.
• Fulcrumalso pivot point
  The stationary pivot point around which a lever rotates.
• Galilean invariancealso Newtonian relativity
  The principle that the fundamental laws of motion hold true in all inertial frames of reference.
• IMAalso ideal mechanical advantage
  Ideal mechanical advantage is the theoretical force multiplication of a machine assuming zero friction.
• Impulsive
  A force applied over an extremely short duration creates a sudden change in momentum.
• Indifferentalso neutral
  A state of neutral equilibrium means a displaced object will neither return to its original position nor move further away.
• Kinetics
  The branch of classical mechanics that analyzes how forces and torques cause motion in physical bodies.
• Lagrangian
  A mathematical function that summarizes the dynamics of a system by subtracting potential from kinetic energy.
• Mass distribution
  The physical arrangement of material weight throughout a solid body.
• Mean free time
  The average duration a particle travels between collisions in a fluid system.
• Mechanical advantage
  The factor by which a mechanism multiplies the force applied to it.
• Mechanobiology
  The study of how physical forces alter the mechanics of biological cells and tissues.
• Momentalso moment of force
  The tendency of a force to rotate an object about an axis or pivot.
• Momentless
  Describing a structural state or connection where no bending forces or torques are transmitted.
• Newton's first lawalso law of inertia
  The principle that a body remains at rest or in uniform motion unless acted upon by a net external force.
• Newton's second law
  The principle that the force applied to a body equals its mass multiplied by its acceleration.
• Newton's third law
  The principle that every action force generates an equal and opposite reaction force.
• Newtonian mechanicsalso classical mechanics
  The branch of physics that describes the motion of macroscopic bodies under the influence of forces.
• Normal modealso mode shape, natural mode
  A pattern of motion in which all parts of a system oscillate with the same frequency and fixed phase.
• Parallelogram of forces
  A graphical method for finding the resultant of two forces acting at a single point.
• Pendulum
  A weight hanging from a single point that oscillates side to side due to gravitational pull.
• Polygon of forces
  A graphical method for determining the resultant of multiple forces acting on a single point.
• Power
  The rate at which work is done or energy is transferred over time.
• PVT
  The relationship between pressure, volume, and temperature in a fluid system.
• Resistance distancealso load arm
  The physical distance from the fulcrum of a lever to the point where the load or resistance is applied.
• Sandwich theory
  A mathematical framework used to analyze the stresses and deflections in composite sandwich structures.
• Screw theory
  A mathematical framework used to describe the kinematics and dynamics of rigid bodies.
• Self-right
  To automatically return to an upright or stable orientation after being tipped over.
• Shear centrealso center of flexure
  The specific point on a beam cross-section where an applied transverse load causes bending without twisting.
• Simple harmonic motionalso SHM
  A periodic oscillation where the restoring force is directly proportional to the displacement.
• Sleep
  To rotate at high speed with such perfect balance that the object appears completely stationary. Shop talk
• Time historyalso time-history analysis, transient analysis
  A record or simulation of how a variable changes over a specific period.
• Torsionalso twisting
  The twisting of an object due to an applied rotational force.
• Varignon's theorem
  A principle stating that the moment of a resultant force equals the sum of the moments of its components.
• Virial
  A scalar quantity used in mechanics to relate the kinetic energy of a system to the forces acting on its particles.

How solid materials deform, resist stress, and ultimately fail under applied heavy loads.

• Barrelingalso barrelling
  A deformation mode where a compressed cylinder bulges outward at its midsection.
• Breaking pointalso ultimate tensile strength, failure point
  The exact stress level at which a material fractures or fails completely.
• Brittle fracture
  A sudden mechanical failure that occurs without prior yielding or plastic deformation.
• Bucklealso buckling
  To suddenly bend or collapse under a compressive load.
• Couponalso test coupon
  A standardized sample of material used for mechanical testing.
• Deformation
  The change in shape or size of a component under an applied load.
• Gussetalso gusset plate
  A flat plate or bracket welded or bolted across a joint to reinforce it against bending and shear forces.
• Honeycomb sandwichalso honeycomb panel, sandwich structure
  A composite panel featuring a lightweight cellular core bonded between two thin, rigid facing sheets.
• Sandwich beam
  A structural beam made by bonding two thin, stiff outer skins to a lightweight, thicker core.
• Sandwich shell
  A curved structural panel consisting of a lightweight core bonded between two thin, rigid outer layers.
• Shimstockalso shim stock
  Thin sheets or rolls of precision-thickness material used to cut custom spacers. Shop talk

The techniques and software used to draft, simulate, and refine mechanical components.

• Bracketry
  The collective assortment of brackets and mounting hardware in an assembly. Shop talk
• Cavity
  A hollow space or depression machined into a solid component, mold, or die.
• CFD
  Computational Fluid Dynamics, the use of software to simulate and analyze fluid flow and heat transfer.
• Computational fluid dynamics
  The use of numerical analysis and algorithms to solve and analyze problems involving fluid flow.
• Explicit modelingalso direct modeling
  A direct computer-aided design approach where geometry is created and modified without a history tree.
• FEMalso FEA
  The finite element method, a numerical technique for solving complex engineering problems.
• Implicit modeling
  A CAD technique that defines 3D geometry using continuous mathematical functions rather than boundaries.
• Orthographically
  Representing a three-dimensional object in two dimensions using parallel projection lines.
• Pseudochannel
  A theoretical flow path used in fluid dynamics to model complex branching flows.
• Rebatalso rebatment
  To rotate an orthographic view into the plane of another view for drafting purposes.
• Solid modelalso 3D model
  A complete 3D digital representation of a part that includes volume and mass properties.

The practical work of inspecting, repairing, and adjusting machinery to keep it running.

• Broken inalso run in
  Describes mechanical parts that have worn together to achieve their final operating fit.
• Engine house
  A dedicated building constructed to enclose and support large stationary power plants.
• Heath Robinsonalso jury-rigged, Rube Goldberg
  A makeshift, overly complicated, or fragile mechanical fix. Shop talk
• Jack
  A portable mechanical or hydraulic device lifts heavy loads over short distances.
• Limit switch
  An electromechanical sensor triggered by the physical motion of a machine part.
• Lock upalso seize, bind
  To suddenly seize or stop moving due to mechanical failure or friction. Shop talk
• Monkey wrenchalso Ford wrench, auto wrench
  A heavy-duty adjustable wrench with smooth jaws that remain strictly parallel. Shop talk
• Overhaulalso rebuild
  To completely disassemble, inspect, repair, and rebuild a machine to restore it to working condition.
• Overspeed
  To drive a machine or engine past its maximum safe rotational limit.
• Postmechanical
  Occurring after the completion of a physical operation or machining process.
• Run-inalso break-in
  The initial operating period of a new or rebuilt machine during which mating parts wear into a precise fit.
• Safetyalso safety catch, safety lock
  A mechanical catch or interlock designed to prevent the accidental actuation of a machine or tool.
• Shimming
  The process of inserting thin spacers to adjust clearances or align components. Shop talk
• Spinalso spin a bearing
  The catastrophic failure of a plain bearing where the insert breaks loose and rotates with the shaft. Shop talk
• Torquealso torquing
  To tighten a threaded fastener to a specific rotational force. Shop talk
• Vibrator
  A mechanical device designed to generate controlled oscillations or shaking.