Odisha CHSE +2 Vocational PDFM (RMPDFM) flashcards

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

Shrinkage allowance

Extra size added to a pattern to compensate for metal contraction on cooling; roughly 1-2% for cast iron and about 1.3% for steel, applied in all directions.

Draft allowance

Taper given to vertical faces of a pattern so it can be withdrawn from the sand without tearing the mould; typically 1 to 3 degrees.

Riser in casting

A reservoir of molten metal that feeds the casting during solidification and must solidify after the casting to prevent shrinkage cavities.

Core and chaplet

A core forms internal cavities in a casting; chaplets are metal supports that hold the core in position against buoyancy during pouring.

Bend allowance

Length of the neutral axis in a bend, calculated as angle in radians multiplied by (inside radius plus K times thickness), added to flat length.

Tap drill size

Drill diameter for tapping a thread, approximately major diameter minus pitch; for M10 x 1.5 the tap drill is 8.5 mm.

Drilling spindle speed

Rotational speed N = (1000 x V)/(pi x D), where V is cutting speed in m/min and D is drill diameter in mm.

First-angle projection

Projection method where the object lies between observer and plane; the top view appears below the front view and the left view on the right.

Representative fraction

Ratio of drawing length to actual length, written as 1:n for a reducing scale; for example 1:20 means 1 mm represents 20 mm.

H7/g6 fit

ISO hole-basis fit designation: H7 is the hole tolerance and g6 the shaft tolerance, producing a close running fit with small clearance.

Hidden line convention

Dashed thin lines represent edges not visible in the view; they are avoided in dimensioning, where dimensions are placed on true-shape views.

Grey cast iron carbon

Grey cast iron contains about 2 to 4 percent carbon, mostly as flake graphite, giving good compressive strength, damping and castability but low ductility.

Annealing purpose

Heat treatment of heating and slow cooling to soften metal, relieve internal stresses and refine grain, improving machinability after casting or welding.

Hacksaw blade pitch

Number of teeth per inch; use 14 TPI for thick sections, 18 general and 24 for thin tube, ensuring at least three teeth engage the work.

Vernier least count

Difference between one main scale division and one vernier division; a 50-division vernier on a 1 mm scale gives a least count of 0.02 mm.

Micrometer least count

Screw pitch divided by number of thimble divisions; a 0.5 mm pitch screw with 50 divisions gives a least count of 0.01 mm.

Accuracy versus precision

Accuracy is closeness of a measurement to the true value; precision is repeatability of readings. Systematic errors affect accuracy, random errors affect precision.

Pareto chart

A bar chart of defects ordered by frequency, used in quality control to show that a few causes account for most problems.

Stress and strain

Stress is force divided by cross-sectional area in N/mm2 (MPa); strain is change in length divided by original length, a dimensionless ratio.

Taper formula

Taper equals (large diameter minus small diameter) divided by length; the half-angle is found from tan(theta) = (D - d)/(2L).

Ohm's law

Voltage equals current multiplied by resistance (V = I x R); electrical power P = V x I = I squared R, and energy in kWh is watts times hours divided by 1000.

Break-even quantity

Number of units to sell where total revenue equals total cost, computed as fixed cost divided by (selling price minus variable cost per unit).

Udyam registration

Online Indian government portal where micro, small and medium enterprises register to obtain MSME benefits, based on investment and turnover criteria.

Communication feedback loop

Communication requires sender, message, encoding, channel, receiver, decoding and feedback; noise is any interference that distorts the message.

Seven Cs of communication

Guidelines for effective messages: clear, concise, concrete, correct, coherent, complete and courteous, applied to letters, reports and emails.

CAD object snap

Precision drawing aid that locks the cursor to exact geometric points such as endpoint, midpoint, centre or intersection, ensuring accurate CAD geometry.

DXF file format

Drawing exchange format used to share CAD drawings between different software packages; DWG is the native format and PDF is used for viewing.

Absolute cell reference

Spreadsheet reference such as $A$1 that stays fixed when a formula is copied, unlike relative references which adjust to the new position.

Silicosis hazard

Lung disease caused by inhaling fine silica dust in foundries and sand blasting; prevented by dust extraction, wet methods and approved respirators.

Arc eye

Painful inflammation of the cornea caused by ultraviolet light from welding arcs; prevented by welding screens, helmets and correct filter shade.

Noise action level

Exposure at or above 85 dB(A) averaged over eight hours requires hearing protection and noise control measures; sound level meters measure this.

Burn first aid

Cool the burn with clean running water for at least 20 minutes, cover with a sterile non-stick dressing, and never apply oil or ice.