Maharashtra SSC Mechanical Technology Pre-Voc/NSQF key terms

Wearable safety gear such as goggles, gloves, apron, safety shoes and helmet that shields the worker from sparks, chips, sharp edges, heat and electrical hazards in the workshop.

The practice of keeping floors, benches and machines clean and clear of chips, oil, scrap and tools so that slips, trips and fire risks are avoided in the workshop.

Fixed or interlocked covers fitted over rotating parts such as gears, belts, chucks and shafts to prevent the operator's hands or clothing from being caught.

A metal made by melting two or more elements together so that the mixture gains properties, such as strength or corrosion resistance, that the pure metal lacks.

Any metal whose main constituent is iron, such as mild steel, cast iron and high carbon steel; these are magnetic and contain iron as the base element.

A metal that contains no iron as its base element, such as aluminium, copper, brass, zinc or lead; these resist rust and are generally lighter and softer.

Controlled heating and cooling of a metal to change its internal structure and therefore its hardness, strength, toughness or machinability without changing its shape.

A softening process in which metal is heated to a suitable temperature and then cooled very slowly, usually in the furnace, to relieve internal stress and improve machinability.

Heating steel above its critical temperature and quenching it rapidly in water or oil so that it becomes very hard and wear-resistant, though more brittle.

Reheating hardened steel to a lower temperature and cooling it to reduce brittleness and relieve stress while keeping a useful level of hardness and toughness.

A measuring instrument with a main scale and a sliding vernier scale used to read outside, inside and depth dimensions to a least count of usually 0.02 mm.

The smallest measurement an instrument can read reliably; for a vernier caliper it equals one main scale division minus one vernier scale division.

A precision measuring instrument using a calibrated screw and thimble to measure small outside dimensions, commonly reading to 0.01 mm with better accuracy than a vernier caliper.

A reading shown by an instrument when the jaws or anvils are fully closed but the scale does not read zero; it must be added or subtracted to correct measurements.

A heavy, accurately machined flat cast iron or granite plate used as a true reference surface for marking out, checking flatness and supporting work during inspection.

A sharp-pointed hardened steel tool used to scratch fine layout lines on metal surfaces during marking out, usually guided along a rule or try square.

An L-shaped checking and marking tool with a hardened steel blade set at exactly 90 degrees to a stock, used to test squareness and to mark right angles.

A clamping device fixed to a workbench, with two jaws opened and closed by a screw, used to hold jobs securely during filing, sawing, chipping and tapping.

A hardened steel hand tool with rows of cutting teeth on its faces, used to remove small amounts of metal and to bring a job to shape, size and finish.

A hand saw with a thin, fine-toothed hardened blade held under tension in a frame, used to cut metal bars, pipes and sheet to length.

A rotating cutting tool with helical flutes and a pointed tip, held in a drill chuck or machine spindle, used to produce round holes in metal and other materials.

A machine in which a vertical spindle rotates a drill bit that is fed downward into a clamped workpiece to cut a hole; the pillar type is common in workshops.

A hardened, threaded cutting tool used by hand or machine to cut an internal thread inside a drilled hole, usually supplied as taper, second and bottoming taps.

A hardened steel tool with an internal thread that is rotated over a rod to cut an external thread, often held in a die stock for hand threading.

The diameter of the hole drilled before tapping, calculated as the nominal thread diameter minus the thread pitch, so that the tap cuts cleanly without breaking.

A machine tool that rotates the workpiece about a horizontal axis while a single-point tool is fed against it to turn, face, bore, knurl or cut threads.

A device mounted on the lathe spindle, with three or four jaws that grip and centre the workpiece so it rotates with the spindle during machining.

A lathe operation in which a single-point tool removes metal from the outside of a rotating cylindrical workpiece to reduce its diameter and improve surface finish.

A fusion welding process in which an electric arc between an electrode and the workpiece produces intense heat that melts the metal and forms a joint.

A metal rod, often coated with flux, that carries the welding current, melts into the joint as filler metal and, in coated form, shields the molten pool from air.

A joining process in which a non-ferrous filler metal with a melting point above 450 degrees Celsius but below that of the parent metal is drawn into a heated joint by capillary action.

A joining process using a low-melting filler metal, usually a tin-lead or lead-free alloy melting below 450 degrees Celsius, with flux to bond metal parts electrically or mechanically.

A drawing method in which front, top and side views of an object are projected onto planes at right angles, showing true shape and size without perspective distortion.

A pictorial drawing in which the three axes are spaced 120 degrees apart and lengths are drawn to the same scale, giving a single three-dimensional view of the object.

The system of adding sizes, notes, arrows and extension lines to a drawing so that the object can be manufactured exactly to the intended measurements and tolerances.

The total permissible variation in a dimension, being the difference between the upper and lower limits within which a part must be made to function correctly.

A gauge with go and no-go ends used on the shop floor to check quickly whether a part dimension lies within its specified upper and lower limits.

A device such as a bolt, nut, screw, rivet or pin used to hold two or more parts together, either permanently or so that they can be taken apart again.

A wrench that indicates or limits the turning force applied to a fastener, ensuring bolts are tightened to a specified value and not overstressed or loosened by vibration.

A nut designed to resist loosening under vibration, by an inserted nylon collar, a deformed thread, a split pin or a second jam nut tightened against it.

Scheduled inspection, cleaning, lubrication and adjustment of machines and equipment carried out before breakdown occurs, to keep them reliable and extend their service life.

Repair work done only after a machine has failed and stopped production; it is reactive, usually costs more and causes unplanned downtime compared with planned maintenance.

Applying oil, grease or another lubricant between moving surfaces to reduce friction and wear, carry away heat and protect parts from rust and corrosion.

A workplace organisation method with five steps: sort, set in order, shine, standardise and sustain, used to create a clean, safe and efficient work area.

A Japanese term meaning continuous improvement; small, ongoing changes made by the whole team to processes, tools and working methods to raise quality and productivity.

The activities used to check that products meet specified requirements, including inspection, measurement, testing and rejection or rework of items that fail.

Giving full attention to a speaker, noting the main points and confirming understanding by asking questions or restating, so that instructions are followed correctly.

Clear exchange of information, instructions and feedback among workers and supervisors through speech, writing, drawings, signs and reports so that work is done safely and correctly.