Maharashtra SSC Mechanical Technology Pre-Voc/NSQF flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Least count of vernier calliper

The smallest measurement a vernier calliper can read, found by dividing one main scale division by the number of vernier divisions. A 1 mm main scale with 50 vernier divisions reads 0.02 mm.

Tap drill size formula

For metric threads, subtract the pitch from the major diameter to get the tapping drill diameter. For example, an M10 thread with 1.5 mm pitch needs an 8.5 mm drill.

First-angle projection arrangement

The object lies between the observer and the projection plane. The top view is therefore placed below the front view, and the left side view appears to the right of the front view.

Annealing purpose

A heat treatment that softens steel, relieves internal stresses and improves machinability. The steel is heated above the critical temperature and then cooled very slowly, usually in the furnace.

Neutral flame use

An oxy-acetylene flame with equal oxygen and acetylene, giving a well-defined inner cone. It is the standard flame for welding mild steel and most common metals.

Cutting speed formula

Cutting speed V in metres per minute equals pi times diameter in millimetres times spindle speed in rpm, divided by 1000. Rearranged, rpm equals 1000V divided by pi times diameter.

Class C fire extinguisher

A fire involving live electrical equipment. Only carbon dioxide or dry powder extinguishers may be used, because water and foam conduct electricity and risk electrocution.

Brazing temperature range

A joining process using a filler metal that melts above 450 degrees Celsius but below the melting point of the parent metals. The parent metal does not melt during brazing.

Clearance fit definition

A fit in which the largest shaft is always smaller than the smallest hole, so a gap always exists between the mating parts. It allows free relative movement.

Tolerance definition

The total permissible variation in a dimension, calculated as the difference between the upper limit and the lower limit. A smaller tolerance demands more accurate machining.

Micrometer least count

The smallest reading of a micrometer, equal to the screw pitch divided by the number of thimble divisions. A 0.5 mm pitch with 50 divisions gives 0.01 mm.

Grey cast iron properties

Cast iron with graphite in flake form, giving good machinability, damping capacity and wear resistance but low tensile strength and ductility. It is used for machine beds and housings.

Carburising process

A case-hardening treatment that adds carbon to the surface of low-carbon steel by heating it in contact with a carbon-rich medium, then hardening to give a hard wear-resistant skin.

Star-delta starter function

A motor starter that connects the motor windings in star during starting and in delta for running. Starting current and torque are reduced to about one third of direct-on-line values.

Earthing purpose

Connecting the metal body of equipment to earth so that a fault current flows and trips the protective device, preventing electric shock to the operator.

Spring washer function

A split, springy washer placed under a nut or bolt head. Its spring action maintains clamping force and resists loosening caused by vibration during machine operation.

Dowel pin purpose

A plain cylindrical pin fitted into reamed holes in two parts to locate them accurately and resist shear. It keeps assembled components aligned during subsequent machining or use.

Preventive maintenance meaning

Scheduled servicing and inspection carried out before failure occurs, such as lubrication, belt checks and cleaning. It reduces breakdowns and extends machine life.

Accuracy versus precision

Accuracy is how close a measured value is to the true value. Precision is how closely repeated measurements agree with each other, regardless of whether they are correct.

NSQF level range

The National Skills Qualifications Framework grades qualifications from level 1 to level 10 by complexity and autonomy. Each qualification pack states its level and credits.

File card purpose

A stiff-bristled brush used to clean metal chips from the teeth of a file. Chips left in the teeth cause pinning, scratch the work surface and reduce cutting efficiency.

Surface plate function

A flat, accurately machined reference surface used for marking out, inspection and checking flatness. Its surface is kept clean and lightly oiled to prevent rust and damage.

Hacksaw blade pitch choice

Blade pitch is selected by work thickness. Coarse blades of 14 teeth per inch suit thick sections; 24 to 32 teeth per inch suit thin tube and sheet to avoid tooth breakage.

Facing operation on lathe

A lathe operation that produces a flat surface at the end of a workpiece by feeding the tool radially across the rotating work while the work rotates about its axis.

Tailstock offset taper turning

A taper turning method in which the tailstock is set over by a calculated amount so the work axis is inclined to the lathe bed. Offset equals the diameter difference times job length divided by twice the taper length.

Third-angle projection symbol

A drawing symbol showing a truncated cone with the small end toward the observer. It indicates third-angle projection, where the top view is placed above the front view.

Section view hatching

Parallel thin lines drawn at about 45 degrees on cut surfaces in a section view. Adjacent parts in an assembly are hatched in opposite directions to distinguish them.

Spot welding principle

A resistance welding process in which current passes through overlapping sheets held between copper electrodes. Heat generated at the interface forms a small welded nugget.

Soldering flux function

A chemical that removes oxide from the metal surfaces and prevents new oxide forming during soldering, allowing the molten filler to wet and bond to the joint.

Job card purpose

A workplace document that records the work assigned, operations carried out, time taken and quantity produced by a worker, used for tracking and payment.

Feedback in communication

The receiver's response that confirms whether the message was understood as intended. Without feedback, the sender cannot know if communication was effective.

Dial indicator use

A measuring instrument with a spring-loaded plunger and graduated dial, used to check runout, alignment, flatness and backlash. The plunger is set against the surface being checked.