Assam ASSEB HS Skill Mechanical Engineering Technology key terms

A drawing method that shows a three-dimensional object as separate two-dimensional views, each looking straight at one face, with front, top and side views aligned to each other.

A projection convention in which the object sits between the observer and the plane, so the view placed on the right of the front view shows the left side of the object.

A projection convention in which the plane lies between the observer and the object, so the view on the right of the front view shows the right side, as used on many Indian and American drawings.

A pictorial view drawn with the three axes at 120 degrees to each other, so all three dimensions are shown to the same scale and true lengths along the axes are preserved.

A view produced by imagining the object cut by a plane and removing the near part, with the cut surface shown by evenly spaced hatching lines to reveal internal features.

A system of symbols and frames that specifies allowable variation in form, orientation, location and runout of features, rather than giving only linear sizes.

The permitted range of sizes for a shaft and hole and the resulting looseness or tightness when they are assembled, classified as clearance, interference or transition fits.

The total permissible variation in a dimension, equal to the difference between the upper and lower limits, expressed so that parts still function when made anywhere within that band.

A measure of the fine irregularities left on a machined surface, usually stated as an average deviation value in micrometres and marked on drawings with a surface texture symbol.

A named, switchable grouping in a drawing file that holds related geometry, letting the user hide, lock or colour parts of a design without deleting them.

A manufacturing process in which molten metal is poured into a mould cavity and allowed to solidify, producing a shape close to the finished part.

A replica of the part used to form the mould cavity in sand casting, made slightly larger than the casting to allow for metal shrinkage during cooling.

A reservoir of molten metal connected to the casting that feeds liquid metal as the part shrinks, preventing shrinkage cavities in the solidifying casting.

A joining process that melts or fuses the edges of two parts, with or without filler metal, to form a continuous metallurgical bond on cooling.

A joining process in which a filler metal with a melting point below that of the parts is drawn into the joint gap by capillary action without melting the base metal.

The region of base metal next to a weld that is not melted but whose microstructure and properties change because of the heat of welding.

A machine tool that rotates the workpiece against a cutting tool fed along or across the axis, used for turning, facing, drilling and threading cylindrical parts.

The rate at which the surface of the workpiece moves past the cutting tool, usually expressed in metres per minute and reduced for harder materials.

A machine tool in which a rotating multi-tooth cutter is fed into a workpiece held on a table, producing flat surfaces, slots and complex profiles.

Steel containing deliberately added elements such as chromium, nickel or molybdenum, in amounts above normal residual levels, to improve hardness, toughness or corrosion resistance.

An iron-carbon alloy whose main alloying element is carbon, with only small amounts of other elements, classified as low, medium or high carbon by carbon content.

A material's resistance to localised plastic deformation, such as indentation or scratching, commonly measured by Brinell, Vickers or Rockwell tests.

The maximum engineering stress a material can carry before necking and fracture in a tensile test, obtained by dividing peak load by the original cross-sectional area.

A test in which a notched specimen is struck by a swinging pendulum to measure the energy absorbed, indicating the material's toughness and tendency to fail in a brittle manner.

The ability of a steel to harden to a given depth below the surface during quenching, determined mainly by its composition and measured by the Jominy end-quench test.

A single force that produces the same effect on a body as a system of several forces acting together, found by vector addition of the individual forces.

The state of a body at rest or in uniform motion, in which the vector sum of all forces and the sum of all moments acting on it are both zero.

The turning effect of a force about a point, equal to the force multiplied by the perpendicular distance from the point to the line of action.

A sketch of an isolated body showing all external forces and moments acting on it, with supports replaced by their reaction forces, used to set up equilibrium equations.

The internal force per unit area developed in a material to resist deformation, usually expressed in newtons per square millimetre or megapascals.

The deformation of a material per unit of its original length, a dimensionless ratio of change in length to original length.

The ratio of direct stress to direct strain within the elastic range of a material, a measure of stiffness expressed in the same units as stress.

A basic device such as a lever, pulley, inclined plane or screw that changes the magnitude or direction of an applied force without adding energy.

The ratio of the load overcome by a machine to the effort applied to it, indicating how many times the machine multiplies the applied force.

The ratio of useful work output to work input for a machine, expressed as a percentage and always below 100 because of friction losses.

The principle of energy conservation applied to a system, stating that net heat supplied equals the change in internal energy plus work done by the system.

A thermodynamic property defined as internal energy plus the product of pressure and volume, useful for analysing steady-flow processes such as boilers and turbines.

A process in which no heat is transferred to or from the system, so any work done causes a corresponding change in internal energy and temperature.

The mass of dry saturated vapour in a mixture divided by the total mass of the mixture, indicating how much of the wet steam is vapour rather than liquid.

A closed pressure vessel in which water is heated by burning fuel to generate steam at a pressure above atmospheric for power or process use.

The sequence of suction, compression, power and exhaust strokes that a piston makes in four movements of the crankshaft, completing one working cycle in two revolutions.

The ratio of the cylinder volume before compression to the volume after compression, a key parameter affecting the power and efficiency of an engine.

The statement that mass flow rate is constant along a stream tube, so the product of density, cross-sectional area and velocity is the same at every section.

An energy relation for steady, incompressible, frictionless flow stating that pressure energy, kinetic energy and potential energy per unit weight sum to a constant along a streamline.

A fluid property that measures resistance to shear flow, equal to the shear stress divided by the velocity gradient, and which falls as temperature rises for liquids.

A rotodynamic pump that uses a rotating impeller to throw liquid outward, converting the velocity imparted to the liquid into pressure at the casing outlet.

The formation and collapse of vapour bubbles in a liquid where local pressure drops below vapour pressure, causing noise, loss of performance and damage to pump or turbine surfaces.

The relationship stating that current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance, at constant temperature.

An alternating supply using three voltages of equal magnitude displaced by 120 electrical degrees, which delivers constant power and drives industrial motors efficiently.

An AC motor in which currents induced in the rotor by the rotating stator field produce torque, the most common drive for industrial machinery.

The deliberate connection of exposed metalwork or a circuit point to the general mass of earth, providing a low-resistance path so protective devices operate during a fault.

Clothing and gear such as helmets, goggles, gloves and safety shoes worn to shield a worker from hazards that cannot be removed by engineering controls.

A procedure that isolates energy sources and attaches personal locks and warning tags before maintenance, ensuring equipment cannot be started while someone is working on it.

A written authorisation that records the hazards, precautions and responsible persons for a high-risk job, and must be signed before work starts and closed after completion.

A workplace condition such as dust, noise, heat, vibration or chemical exposure that can cause illness or injury over time if not controlled.

The activity of identifying an opportunity, organising resources and bearing the risk of starting and running a business venture to create value.

The level of sales at which total revenue equals total cost, so the business neither makes a profit nor a loss, found by dividing fixed costs by contribution per unit.

The funds tied up in day-to-day operations, calculated as current assets minus current liabilities, needed to pay for materials, wages and overheads before sales are collected.

A short written summary of a person's education, skills, experience and achievements, tailored to the job applied for and used by employers to shortlist candidates.

Non-technical workplace abilities such as communication, teamwork, punctuality and problem solving that determine how effectively a person works with others.