BA Threads - Clearance and tapping drill sizes for BA threads.
Back Gears - Gears fitted to a machine to increase the number of spindle speeds obtainable with a cone or step pulley belt
Back Weld - A weld deposited at the back of a single groove weld.
Backhand Welding - A welding technique in which the flame is directed towards the completed weld.
Backing Strip - A piece of material used to retain molten metal at the root of the weld.
Backing Weld - A weld bead applied to the root of a single groove joint to assure complete root penetration.
Backlash - The lost motion or looseness (play) between the faces of meshing gears or threads.
Backstep - A sequence in which weld bead increments are deposited in a direction opposite to the direction of progress.
Baghouse Filter - A fabric filter device used to remove particulate air pollutants.
Bainite - An austenitic transformation product found in some steels and cast irons.
Balanced Construction - A method of constructing manufactured wood products so that moisture content changes will be
uniformly distributed and therefore will not cause warping.
Balancing - A procedure for adjusting the mass distribution of a rotor so that vibration of journals, or the forces on the
bearings at once-per-revolution, are reduced or controlled.
Ball Peen Hammer - A hammer with two ends on the head, one that is round and the other flat.
Ball Valve - a shutoff valve of the packed type that incorporates a round, internal dynamic member, or "ball," and containing
one or more through holes that connect the ports of the valve to each other.
Ballistics - Ignoring the curvature of the Earth, frictional losses and that g is constant it is possible to calculate the trajectory
of a projectile that is fired with a given initial velocity and elevation.
Ballscrew - A threaded shaft and nut assembly supported by angular contact bearings, normally found on machine tools.
Balsa Wood - The wood from Ochroma Lagopus.
Bandsaw - A power saw, the blade of which is a continuous, narrow, steel band having teeth on one edge and passing over
two large pulley wheels.
Bandwidth - The bandwidth of a filter is the separation between the lower and upper frequencies at which the amplitude of a
sinusoidal signal is attenuated by a factor of 2.
Bar Clamp - A tool with a stationary head and a sliding foot for clamping purposes.
Bar Stock - Metal bars of various lengths, made in flat, hexagon, octagon, round, and square shapes from which parts are
Barrel - A unit of capacity in the oil industry.
Barye - The CGS unit of pressure, equal to 1 dyne per square centimetre.
Base Metal - The metal to be welded or cut. In alloys, it is the metal present in the largest proportion.
Baseplate - The surface to which the feet of a machine are attached.
Bastard - Threads, parts, tools, and sizes that are not standard.
bbl - Abbreviation of barrel. A unit of capacity in the oil industry.
BDC - Abbreviation of bottom dead centre.
Beam Bridge - A bridge whose main structural element consists of a beam set across two or more vertical supporting
Bearing - Primarily two types, rolling element and sleeve or plain bearing.
Bearing Misalignment - A misalignment that results when the bearings supporting a shaft are not aligned with each other.
Bearing Nomenclature - Codes specific to the bearing manufacturer that describe the material, clearance, construction and
Beech - A very hard wood almost unaffected when exposed to water. Therefore, it is used for keels of ships and flood gates.
On account of its hardness it was used for wheels and railway sleepers.
Beeswax - Produced by bees to make their honeycombs.
Bell Mouth - The flaring or tapering of a machined hole, usually made at the entrance end because of misalignment or spring
of the cutting tool.
Belt Drive - A belt used to transmit power between two shafts.
Belt Noise - There are many different mechanisms by which drive belts generate noise.
Belville Washer - Often used on smaller angular contact arrangements to provide a preload.
Bench Grinder - A small grinding machine for shaping and sharpening the cutting edges of tools.
Bench Lathe - A small lathe mounted on a bench or table.
Bench Work - Work done primarily at a bench with hand tools.
Bending Stress - Stress on the cross-sectional area of a beam due to the bending moment of the beam under load.
Bernoulli’s Law - A change in the velocity of a fluid caused by a constriction produces an opposite change in pressure.
Beta Stirling Engine - A stirling engine with a single power piston arranged coaxially with a displacer piston.
Bevel - Any surface that is not at right angles to another surface. Also, the name given a tool used for measuring, laying out,
or checking the accuracy of work machined at an angle or bevel.
BHN - Abbreviation of Brinell Hardness Number.
BHP - Brake Horse Power, the useful power available at the flywheel of an engine.
Big End - The connection between the conrod and crankshaft in an internal combustion engine.
Billet - Rectangular or square bar of raw material.
Bill of Material - a hierarchical list of materials required to produce an item, showing the quantity of each required item
Bimetallic Strip - Two metals with different thermal expansion coefficients are bonded together and wound into a spiral.
Biochemical oxygen demand (BOD) The amount of oxygen required to oxidize any organic matter present in a water during a
specified period of time, usually 5 days. It is an indirect measure of the amount of organic matter present in a water.
Biomass — Renewable organic matter such as trees, plants, animal waste, industrial waste recycled paper
Biot-Fourier Equation - An equation for heat conduction which states that the rate of change of temperature at any point
divided by the thermal diffusivity equals the Laplacian of the temperature.
Birch - Strong flexible wood that has many uses. Amongst the uses are furniture making, building as well as being used for
agricultural implements in the past.
Birmingham Sheet Metal Gauge - This is a numbering system for sheet metal gauge (thickness).
Black Annealing - Box annealing or pot annealing ferrous alloy sheet, strip or wire.
Black Box - A unit whose output is a specified function of the input, but for which the method of converting input to output is
not necessarily specified.
Black Light - Electromagnetic radiation not visible to the human eye.
Blacksmith Hammer - A special hammer for hitting and shaping heated iron.
Blacksmithing - The ancient art of forging and working metal, especially iron.
Blade - An arm of a propeller or a rotating wing.
Blade Passing Frequency - A potential vibration frequency on any bladed machine (turbine, axial compressor, fan, etc.). It is
represented by the number of blades times shaft-rotating frequency.
Blank Carburizing - Simulating the carburizing operation without introducing carbon.
Blind Hole - A hole made in a workpiece that does not pass through it.
Block Brazing - A brazing process in which bonding is produced by the heat obtained from heated blocks applied to the parts
to be joined.
Bloom - Generally a rolled product from an ingot generally greater than 36 square inches in area, this is the first operation in
the production of bars or structurals.
Blow By - Passage of unburned fuel and combustion gases past the piston rings of internal combustion engines, resulting in
fuel dilution and contamination of the crankcase oil.
Blowhole - A defect in a casting caused by trapped steam or gas.
Blue Brittleness - Brittleness exhibited by some steels after being heated to some temperature within the range of 150 to
Blueprint - A pen or ink line drawing reproduced (printed) on sensitised paper by direct exposure.
BMEP - Brake Mean Effective Pressure, the average effective cylinder pressure that does useful work calculated from the
brake horse power.
Bobbiere Metal - A brass made with 66% copper and 34% zinc.
BOD - Biochemical oxygen demand
Body Force - An external force acting throughout the mass of a body.
Body Hammer - A hammer with a large flat pounding surface for removing dents.
Bolt - A cylindrical threaded fastener.
BOM - Bill of Materials
Boost Pressure - The increase above atmospheric pressure produced inside the intake manifold by a forced-induction system
such as a turbocharger or supercharger.
Boss - A projection or an enlarged section of a casting through which a hole may be machined.
Bossing Mallet - A hammer with a pear-shaped wooden head used for shaping and stretching metal over a sandbag or
Bottom Dead Centre - The position of the crank when the piston is in its closest position to the crankshaft, in its farthest
position from the cylinder head. Abbreviated bdc.
Box Annealing - Annealing a metal or alloy in a sealed container under conditions that minimize oxidation.
Box Spanner - A hollow tube with a socket at each end and two holes through which a bar can be inserted to turn the tube.
Box Wrench - American name for a ring spanner.
Box-Wood - Very compact hard wood suitable for machining small parts from.
BPSD - Barrels per standard day
Brake Graunch - The name given to the noise made by the brakes when they are just slipping when starting (or stopping)
from rest. The brake graunch is mainly exhibited on the vehicles fitted with automatic transmission, but can also occur on
manual vehicles e.g., on a steep hill. It is caused by brake pad stick-slip when static and dynamic friction is very similar. The
term 'creep/groan' is also used to describe the brake graunch.
Brake Horse Power - This is the useful power available at the flywheel of an engine.
Brake Judder - Brake judder is the phenomenon where with medium to heavy braking from high speed, severe vibration is
felt throughout the whole vehicle. It is often attributed to a mode of vibration in which the front suspension executes a
predominantly fore and aft vibration with the two road wheels in-phase with each other. Excitation is often provided by the
oscillatory forcing generated when applying the brakes to a brake disk that has disk thickness variation.
Brake Mean Effective Pressure - This is the average effective cylinder pressure that does useful work calculated from the
brake horse power.
Brake Pipes - Pipes used to carry hydraulic brake fluid under pressure.
Brake Specific Fuel Consumption - The ratio of the engine fuel consumption to the engine power output.
Brake Squeal - High frequency continuous tone when brakes are applied, this may be a single or multiple tones. The sound is
generated by vibration on the surface of the disc itself.
Brakes - A device used to reduce the speed of a vehicle or object.
Brale - A diamond penetrator of specified sphero-conical shape used with a Rockwell hardness tester for hard metals.
Brass - An alloy of copper and zinc, but often other elements such as aluminium, iron, manganese, tin and lead are added.
Brass Hammer - A hammer with a brass head.
Braze Welding - A method of welding by using a filler metal that liquefies above 450°C and below the solid state of the base
Brazing - Joining metals by flowing a thin layer, capillary thickness, of nonferrous filler metal into the space between them.
Breaking Stress - Also known as the ultimate tensile strength. This is the maximum stress that can be applied to a material.
Bricklayer Hammer - A special hammer for chipping cement blocks and bricks.
Brinell Hardness Test - A test for determining the hardness of a material by forcing a hard steel or carbide ball of specified
diameter into it under a specified load.
Brinelling - A form of mechanical damage in which metal is displaced or upset without attrition.
Bristol Metal - A brass made with 75.5% copper and 24.5% zinc.
British Association Threads - A British system of threads with 47.5° included angle with rounded roots and crest. Even
numbers are the preferred sizes.
British Standard Brass - A specialist thread form based upon the Whitworth thread and consisting of 26 threads per inch
whatever the thread diameter.
British Standard Fine - A thread form based upon the British Standard Whitworth form but with a finer thread.
British Standard Whitworth - A symmetrical V thread with an angle between the threads measured in the axial plane of 55°.
1/6 of the V, i.e. the point is truncated with arcs blended tangentially into the flanks.
British Thermal Unit - The amount of heat required to raise the temperature of 1 pound of water by 1° Fahrenheit.
Brittle Crack Propagation - A very sudden propagation of a crack with the absorption of no energy except that stored
elastically in the body.
Brittle Fracture - Separation of a solid with little or no macroscopic plastic deformation.
Brittleness - The tendency of a material to fracture without first undergoing significant plastic deformation.
Broach - A long, tapered cutting tool with serration′s which, when forced through a hole or across a surface, cuts a desired
shape or size.
Broadband - A transmission medium with enough bandwidth to carry multiple voice, video, or data channels simultaneously.
Bronze - Bronze is an alloy of copper and tin. However, the name is now applied to other alloys that do not contain tin.
Brookfield Viscosity - Apparent viscosity determined by Brookfield viscometer.
Brunel, Isambard Kingdom - Creator of the Great Western Railway, bridge builder and revolutionary naval architect.
Brush DC Motors - The Brush DC motors use commutators and carbon brushes to apply current through the windings as the
Brushless DC Motors - The BLDC motor uses electronic commutation to control the current through the windings.
BSF - A thread form based upon the British Standard Whitworth form but with a finer thread.
BSFC - Brake Specific Fuel Consumption, the ratio of the engine fuel consumption to the engine power output.
BSW - Abbreviation of British Standard Whitworth
BTU - Abbreviation of British Thermal Unit.
Btu h-1 - An abbreviation of British thermal units per hour, the unit of heat flow rate in the British system of units.
Buckling Load - The limit of force beyond which a structure will buckle.
Buff - To polish to a smooth finish of high luster with a cloth or fabric wheel to which a compound has been added.
Bulk Modulus - The bulk modulus of a gas is a measure of its compressibility (elastic property).
Bump Steer - A generally undesirable condition in which a wheel steers slightly as its suspension compresses or extends.
Bumping Hammer - An hammer used with a dolly for restoring a panel′s shape.
Buoyant Force - The upward force exerted by a fluid on a submerged or floating object.
Burgess Vector - A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.
Burnishing - The process of finishing a metal surface by contact with another harder metal to improve it. To make smooth or
glossy by or as if by rubbing; polish.
Burr - The sharp edge left on metal after cutting or punching.
Bushing - A sleeve or a lining for a bearing or a drill jig to guard against wear.
Engineering Glossary, Engineering Dictionary B
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