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ITI/NCVT Sheet Metal Worker (AITT Theory) study materials
ITI/NCVT Sheet Metal Worker (AITT Theory) study resources

ITI/NCVT Sheet Metal Worker (AITT Theory) practice questions

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Question 1Trade Safety, Occupational Health and Environment

In a sheet metal workshop, which fire extinguisher class is specifically intended for fires involving combustible metals such as magnesium and aluminium swarf?

  1. Class D Correct answer.
  2. Class A
  3. Class B
  4. Class C

Explanation

Class D extinguishers use dry powders such as graphite or sodium chloride that smother combustible metal fires by excluding oxygen and absorbing heat. Metal swarf and dust burn at very high temperature and can react violently with water or carbon dioxide, so only a Class D agent is appropriate.

Question 2Trade Safety, Occupational Health and Environment

A guillotine shear operator must keep hands clear of the blade during a cut. Which safeguard is the primary engineered control for this hazard?

  1. Wearing cotton gloves while feeding the sheet
  2. Placing a warning sign on the machine body
  3. A fixed or interlocked guard around the blade and hold-down Correct answer.
  4. Working in pairs so one person watches the blade

Explanation

The hierarchy of controls puts engineering measures first, and for a guillotine the fixed guard with an interlocked feed opening physically prevents hands from entering the blade zone. Warning signs and supervision are administrative controls that only supplement the guard.

Question 3Trade Safety, Occupational Health and Environment

When lifting a heavy sheet of mild steel plate manually, which practice best reduces the risk of back injury?

  1. Bend at the waist, keep legs straight and twist to swing the plate
  2. Hold the plate at arm's length away from the body
  3. Keep the load close to the body, bend the knees and avoid twisting Correct answer.
  4. Lift quickly with a jerking motion to overcome inertia

Explanation

Safe manual handling keeps the load close to the trunk, uses the leg muscles by bending the knees, and keeps the spine from twisting under load. Twisting while bearing weight sharply increases shear stress on the lumbar discs. Team lifting or mechanical aids should be used when the plate exceeds a safe individual weight.

Question 4Trade Safety, Occupational Health and Environment

Which welding process hazard is best controlled by local exhaust ventilation positioned close to the arc?

  1. Exposure to welding fume and metal oxide particulates Correct answer.
  2. Electric shock from the return cable
  3. Noise from the transformer
  4. Ultraviolet radiation of the arc

Explanation

Welding fume contains fine metal oxide particles and gases generated at the arc, and extraction at source captures them before they reach the breathing zone. Local exhaust ventilation is the standard engineering control for fume, while other hazards need different controls such as insulation, screens or hearing protection.

Question 5Trade Safety, Occupational Health and Environment

A worker must enter a closed sheet metal tank that previously held solvent. Which sequence of precautions is correct before entry?

  1. Purge the tank with oxygen and then enter without testing
  2. Ventilate the tank, test the atmosphere, and enter with a standby person and rescue plan Correct answer.
  3. Wear a dust mask and enter alone with a torch
  4. Open the manhole and enter immediately to finish the job quickly

Explanation

Confined space entry requires isolation, ventilation, atmospheric testing for oxygen and flammable or toxic gas, and a trained standby attendant outside with a rescue arrangement. These controls must be in place before anyone enters, because rescue from inside a tank is extremely difficult.

Question 6Trade Safety, Occupational Health and Environment

Why is compressed air never used to blow metal dust off clothing or the skin in a sheet metal shop?

  1. It damages the fabric of the overalls
  2. It is prohibited only because of the noise level
  3. It cools the skin too quickly
  4. It can force particles into the skin or eyes and create an airborne dust cloud Correct answer.

Explanation

A compressed air jet can drive metal particles into soft tissue and eyes, and it disperses fine dust into the breathing zone where it may be inhaled or form an explosive cloud. Low-pressure air with a chip guard, or brushing and vacuum extraction, should be used instead.

Question 7Trade Safety, Occupational Health and Environment

A tin snip used on stainless steel sheet has developed a slightly loose pivot rivet. What is the correct action?

  1. Oil the pivot to take up the slack
  2. Tighten the rivet and check the cutting edges before further use Correct answer.
  3. Swap it with a shear for the rest of the shift and report it later
  4. Continue using it and grip harder to compensate

Explanation

A loose pivot lets the blades cross or slip, which can cause the tool to jump and cut the hand, so the joint must be tightened and the edges inspected before use. Hand tools that cannot be restored to safe condition must be withdrawn from service and reported.

Question 8Trade Safety, Occupational Health and Environment

In a rolling shop, the noise level beside a power shear measures about 92 dB(A) over an eight-hour shift. What does this require under standard occupational noise practice?

  1. No action, because the level is below 100 dB(A)
  2. Only a warning sign at the machine
  3. Rotation of operators every two hours with no hearing protection
  4. Hearing protection and audiometric testing as part of a hearing conservation programme Correct answer.

Explanation

An eight-hour exposure of 92 dB(A) exceeds the usual 85 dB(A) action level, so a hearing conservation programme with hearing protection, training and audiometric testing is required. Engineering noise control at source should also be considered first in the hierarchy of controls.

Question 9Trade Safety, Occupational Health and Environment

During gas welding, a flashback occurs at the torch. What is the correct immediate response and the reason for it?

  1. Increase both gas flows to push the flame back to the tip
  2. Shut the acetylene valve first, then the oxygen valve, to cut off the fuel supply Correct answer.
  3. Leave the torch burning and close the cylinder valves at the regulator
  4. Shut the oxygen valve first, then the acetylene valve, to starve the flame of oxidant

Explanation

A flashback is flame travelling back into the torch or hose, so the fuel gas must be shut off first to remove what the flame is burning, followed by the oxygen. Shutting oxygen first would leave acetylene flowing and feeding the flame. Flashback arrestors on the regulators and torch are the preventive device.

Question 10Trade Safety, Occupational Health and Environment

A press brake operation involves reaching into the die area to position small parts. Which combination of controls best reduces the risk of a crush injury?

  1. Longer gloves and a verbal warning before each stroke
  2. Presence-sensing light curtain interlocked with the stroke plus correctly set tooling and a safe working method Correct answer.
  3. A faster ram speed so the operator's hand is in the die for less time
  4. Foot pedal operation with the operator standing further back

Explanation

A light curtain interlocked to stop the stroke when the beam is broken prevents the ram from closing while hands are in the die, and it must be combined with correct tooling and a method that keeps hands out of the pinch zone. Engineering controls of this type take priority over gloves, warnings or speed changes.

Question 11Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

In a sheet metal drawing, a development (flat pattern) is drawn primarily to show which of the following?

  1. The welding sequence to be followed during fabrication
  2. The assembled position of the component in the machine
  3. The true shape of the unfolded surface before bending Correct answer.
  4. The surface finish required after painting

Explanation

A development unfolds the surface of a sheet metal article onto a single plane so that the true shape and size of each face is visible. This flat pattern is the direct basis for marking and cutting the blank. Assembly position, welding sequence and paint finish are conveyed by other views or notes, not by the development.

Question 12Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A drawing is drawn to a scale of 1:5. A line measuring 36 mm on the drawing represents what actual length?

  1. 180 mm Correct answer.
  2. 41 mm
  3. 7.2 mm
  4. 720 mm

Explanation

A scale of 1:5 means one unit on the drawing represents five units on the object, so the drawing measurement is multiplied by the scale denominator. Here 36 mm × 5 = 180 mm actual length. Dividing instead of multiplying, or adding the scale value, gives the wrong results.

Question 13Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

Which line type is standard for representing hidden edges and outlines in an engineering drawing?

  1. A continuous thin wavy line
  2. A continuous thick line
  3. A chain line of long and short dashes
  4. A dashed line of short equal strokes Correct answer.

Explanation

Hidden outlines and edges are shown by a dashed line made of short strokes of equal length, spaced evenly. Continuous thick lines are used for visible outlines, chain lines for centre lines, and wavy lines for limits of partial views. Using the wrong line type makes the drawing ambiguous to the shop floor.

Question 14Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

On a sheet metal drawing, the symbol consisting of two short parallel lines perpendicular to a fold line indicates which feature?

  1. A centre line of a cylindrical seam
  2. A cut-out to be removed by shearing
  3. A spot weld location on the joint
  4. A bend line where the sheet is to be folded Correct answer.

Explanation

The bend line convention marks the position of a fold and tells the worker where the metal is to be bent. It is placed on the development at the correct distance from the edge. Cut-outs, weld spots and centre lines each have their own distinct conventions and symbols.

Question 15Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A drawing shows a sheet metal component with the title block reading 'Scale 2:1'. A dimension on the object measures 25 mm. What length will that dimension appear on the drawing?

  1. 12.5 mm
  2. 27 mm
  3. 23 mm
  4. 50 mm Correct answer.

Explanation

A scale of 2:1 is an enlargement, so each actual unit is drawn twice its size. Multiplying 25 mm by 2 gives 50 mm on the drawing. Dimensions written on the drawing always state the true size regardless of scale, but the drawn length is enlarged here.

Question 16Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

In a first-angle projection drawing, where is the view from the top of the object placed relative to the front view?

  1. Above the front view
  2. To the right of the front view
  3. To the left of the front view
  4. Below the front view Correct answer.

Explanation

In first-angle projection the object is imagined between the observer and the plane, so the top view is projected onto the plane below and appears below the front view. The view from the left appears on the right, and the view from the right appears on the left. This is the reverse of third-angle projection.

Question 17Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A cylindrical duct of diameter 200 mm is developed as a flat rectangle. Which dimension of the rectangle corresponds to the circumference of the duct?

  1. 628 mm Correct answer.
  2. 314 mm
  3. 400 mm
  4. 200 mm

Explanation

The width of the development equals the circumference of the cylinder, calculated as π × diameter. Using π = 3.14, the circumference is 3.14 × 200 = 628 mm. The diameter itself and half the circumference are not the developed width.

Question 18Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

When developing a truncated cylinder, the heights of the ordinates on the development are taken from which feature of the elevation?

  1. The horizontal width of the elevation
  2. The slant height measured along the cut edge
  3. The vertical distances from the base line to the cut line Correct answer.
  4. The diameter of the cylinder

Explanation

The development of a truncated cylinder requires the true vertical height at each division line, measured from the base line up to the inclined cut. These heights are transferred to the corresponding ordinates on the flat pattern. Slant heights are not used, because the development preserves true lengths measured perpendicular to the base.

Question 19Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A square pyramid is to be developed. Why must the true slant edge length be found before drawing the development?

  1. Because the apex angle is always a right angle
  2. Because the development uses the true length of the slant edge as the radius for laying out the triangular faces Correct answer.
  3. Because the base perimeter is measured along the slant edge
  4. Because the development is drawn to a reduced scale

Explanation

Each face of a pyramid develops as a triangle whose two equal sides are the true slant edge length. If the edge is foreshortened in the plan or elevation, the true length must be obtained by construction or rotation before the arcs can be struck. The base perimeter is laid out separately along the base edges.

Question 20Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A drawing carries the note '3 mm CRCA sheet'. What does this note convey to the sheet metal worker?

  1. The sheet has three corrugations and is made of cast iron
  2. The sheet is 3 mm wide and made of copper alloy
  3. The sheet must be cut into three pieces of carbon steel
  4. The sheet is 3 mm thick and made of cold rolled close annealed steel Correct answer.

Explanation

The figure 3 mm states the material thickness, and CRCA is the standard abbreviation for cold rolled close annealed steel sheet. Thickness governs the bend radius, allowance and tooling selection. The abbreviation does not refer to width, corrugations or the number of pieces.

Question 21Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A seam joint on a sheet metal drawing is shown with a single row of small circles along the lap. What do these circles most likely represent?

  1. Index marks for assembly
  2. Rivets or spot welds fixing the lap joint Correct answer.
  3. Bend relief notches
  4. Holes for ventilation

Explanation

A row of small circles along a lap indicates the fasteners, either rivets or spot welds, that hold the seam. Their spacing and number are read directly from the drawing. Ventilation holes, bend reliefs and assembly marks are shown by different conventions.

Question 22Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

In a drawing of a sheet metal box, the corner where two bends meet is shown with a small circular cut-out. What is the purpose of this feature?

  1. To indicate the grain direction of the sheet
  2. To allow the metal to clear the corner during bending and prevent tearing Correct answer.
  3. To reduce the weight of the box
  4. To provide a hole for a fixing screw

Explanation

A corner relief is provided so that the material at the intersection of two bends does not overlap, pucker or tear when folded. It is a standard feature of box and tray developments. It is not a screw hole, a weight-saving measure, or a grain direction mark.

Question 23Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A drawing shows a tolerance of ±0.5 mm on a developed blank length of 500 mm. What is the permissible range of the blank length?

  1. 499.5 mm to 500.5 mm Correct answer.
  2. 499.5 mm to 501.5 mm
  3. 500.0 mm to 500.5 mm
  4. 499.0 mm to 501.0 mm

Explanation

A bilateral tolerance of ±0.5 mm means the dimension may vary half a millimetre either way from the nominal value. Adding and subtracting 0.5 mm from 500 mm gives a range of 499.5 mm to 500.5 mm. Any wider range would exceed the stated tolerance.

Question 24Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

In third-angle projection, the view placed to the right of the front view represents which side of the object?

  1. The left side
  2. The top
  3. The right side Correct answer.
  4. The bottom

Explanation

In third-angle projection the plane is between the observer and the object, so each view is placed on the same side as the direction from which it is seen. The view to the right of the front view is therefore the right side view. In first-angle projection the arrangement would be reversed.

Question 25Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A development of a cone is laid out as a sector of a circle. The radius of that sector equals which true length of the cone?

  1. The base diameter
  2. The vertical height
  3. The slant height Correct answer.
  4. The base radius

Explanation

When a right cone is unrolled, each generator becomes a radius of the sector, and every generator is equal to the slant height. The arc length of the sector equals the base circumference. The vertical height and base radius are shorter than the slant height and cannot be used as the sector radius.

Question 26Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

When laying out the development of an oblique cylinder, why is the surface divided into a number of equal parallel elements?

  1. To reduce the number of dimensions on the drawing
  2. To avoid the need for a scale
  3. To approximate the curved surface by a series of measurable straight elements whose true lengths can be transferred Correct answer.
  4. To make the drawing look symmetrical

Explanation

An oblique cylinder cannot be developed by a single simple formula, so the curved surface is divided into equal elements. The true length of each element is measured and transferred to the development, and the points are joined to form the curved edge. More divisions give a more accurate curve.

Question 27Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A bend allowance of 2 mm is to be added for each 90° bend in a developed length. A channel section has two 90° bends and a developed straight length of 240 mm. What is the total developed length?

  1. 242 mm
  2. 244 mm Correct answer.
  3. 248 mm
  4. 246 mm

Explanation

Each bend adds its allowance to the flat length, so two bends add 2 × 2 = 4 mm. Adding this to the 240 mm of straight development gives 244 mm. This total is the blank size required before bending.

Question 28Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A drawing shows a component with a dimension marked as a reference dimension in brackets, such as (150). How should the sheet metal worker treat this dimension?

  1. It is the controlling dimension to be measured and inspected
  2. It is the thickness of the material to be used
  3. It is for information only and is not to be used for manufacturing or inspection Correct answer.
  4. It is the maximum permissible size of the part

Explanation

A dimension enclosed in brackets is a reference dimension, given for information or convenience only. It is derived from other dimensions and is not used for production or inspection. The controlling dimensions are the untoleranced or toleranced ones elsewhere on the drawing.

Question 29Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

In the development of a transition piece from a rectangular duct to a round duct, the surface is divided into a set of triangles. What is the essential requirement for each triangle before it is laid out?

  1. The triangle must be equilateral
  2. The triangle must be drawn to full scale
  3. All three sides must be true lengths Correct answer.
  4. The triangle must contain a right angle

Explanation

Triangulation develops a warped surface by treating it as a series of triangles, and each triangle can be laid out only when all three sides are known in true length. Foreshortened edges must first be corrected by rotation or auxiliary views. The triangles need not be equilateral, right angled, or drawn full size.

Question 30Engineering Drawing, Sketching and Reading of Sheet Metal Drawings

A sheet metal drawing indicates the grain direction of the sheet with an arrow. Why is this information important when laying out a bend?

  1. The grain direction determines the welding process
  2. Bending across the grain gives a different result from bending along the grain, affecting cracking and springback Correct answer.
  3. The grain direction sets the tolerance on the blank
  4. The grain direction fixes the material thickness

Explanation

Rolled sheet has a grain direction, and bending parallel to the grain is more likely to crack on the outside of the bend, while bending across the grain behaves differently in springback. The drawing shows the grain so the blank can be oriented correctly on the sheet. Grain direction does not set thickness, welding process or tolerance.

Question 31Materials and Hand Tools for Sheet Metal Work

Which property of a sheet metal makes it suitable for being hammered into a hollow shape without cracking?

  1. High hardness
  2. High malleability Correct answer.
  3. High brittleness
  4. Low ductility

Explanation

Malleability is the ability of a metal to be deformed permanently under compressive force, such as hammering or pressing, without fracture. A malleable sheet can be stretched and formed over a stake or into a die without splitting. Brittle or hard sheets resist deformation and tend to crack instead.

Question 32Materials and Hand Tools for Sheet Metal Work

A sheet metal worker needs a light, corrosion-resistant sheet for a kitchen exhaust hood. Which material is the most common choice for this application?

  1. Stainless steel Correct answer.
  2. Galvanised mild steel
  3. Copper
  4. Aluminium

Explanation

Stainless steel contains chromium that forms a passive oxide layer, giving good corrosion resistance and hygiene, which suits kitchen hoods exposed to steam and grease. It also tolerates cleaning chemicals and moderate heat. Aluminium is light but softer and less resistant to strong cleaning agents, while galvanised steel loses its zinc coating in wet conditions.

Question 33Materials and Hand Tools for Sheet Metal Work

What is the standard designation of the tool used to scribe layout lines on sheet metal without cutting into the surface deeply?

  1. Scriber Correct answer.
  2. Cold chisel
  3. Divider
  4. Punch

Explanation

A scriber is a sharp-pointed steel tool used to scratch fine layout lines on metal surfaces. It produces a narrow, accurate line that guides cutting and bending. A cold chisel cuts metal, a punch marks points, and a divider transfers distances rather than drawing a straight line.

Question 34Materials and Hand Tools for Sheet Metal Work

Which hammer is normally used for general sheet metal forming and riveting because of its light, well-balanced head?

  1. Ball peen hammer Correct answer.
  2. Claw hammer
  3. Sledge hammer
  4. Club hammer

Explanation

The ball peen hammer has a flat face for general striking and a rounded peen for riveting and shaping. Its moderate weight and balance make it suitable for sheet metal work on stakes and formers. A sledge or club hammer is too heavy for controlled sheet forming, and a claw hammer is intended for nails.

Question 35Materials and Hand Tools for Sheet Metal Work

What does the gauge number of a sheet metal indicate?

  1. The length of the sheet in millimetres
  2. The weight of the sheet per square metre
  3. The width of the sheet in inches
  4. The standard thickness of the sheet Correct answer.

Explanation

Sheet metal gauge is a standard numbering system for thickness. A lower gauge number corresponds to a thicker sheet, and the actual thickness varies between material standards. Gauge does not describe length, width or weight directly.

Question 36Materials and Hand Tools for Sheet Metal Work

Which measuring tool is best suited for checking the depth of a recessed flange on a formed sheet metal part?

  1. Try square
  2. Steel rule
  3. Feeler gauge
  4. Vernier caliper Correct answer.

Explanation

A vernier caliper has a depth rod that can measure the depth of a recess or flange to a fraction of a millimetre. A steel rule is less precise and cannot reach into a recess easily. A try square checks squareness and a feeler gauge measures small clearances.

Question 37Materials and Hand Tools for Sheet Metal Work

A sheet of aluminium alloy is bent through a sharp 90 degree corner and cracks on the outside of the bend. Which property most directly explains this failure?

  1. High electrical resistance
  2. High thermal conductivity
  3. Low fatigue strength
  4. Low ductility Correct answer.

Explanation

Cracking on the outside of a bend indicates that the material cannot stretch enough on the tension side, which is a ductility limitation. The outer fibres must elongate during bending, so a low-ductility alloy cracks when the bend radius is too tight. Fatigue, conductivity and electrical resistance do not cause immediate cracking in a single bend.

Question 38Materials and Hand Tools for Sheet Metal Work

Why is zinc coating applied to mild steel sheets in the galvanising process?

  1. To provide a sacrificial protective layer against corrosion Correct answer.
  2. To make the sheet easier to paint without preparation
  3. To improve the electrical conductivity of the sheet
  4. To increase the tensile strength of the steel

Explanation

Zinc is more reactive than iron, so it corrodes preferentially and protects the steel even where the coating is scratched. This is called sacrificial protection. Galvanising does not significantly increase tensile strength and may actually require care during welding.

Question 39Materials and Hand Tools for Sheet Metal Work

A pattern is transferred from a drawing to a flat sheet using a pair of dividers set to a fixed radius. What is this operation called?

  1. Snapping a line
  2. Centre punching
  3. Prick punching
  4. Scribing an arc Correct answer.

Explanation

Dividers have two sharp points and are used to scribe arcs or circles and to step off equal distances on the workpiece. One point is placed at the centre and the other scratches the arc. Centre punching marks a point for drilling, and snapping a line uses a chalked string.

Question 40Materials and Hand Tools for Sheet Metal Work

Which snip is designed for cutting tight curves and small radii in sheet metal?

  1. Aviation snip with curved blades Correct answer.
  2. Straight snip
  3. Hacksaw
  4. Bench shear

Explanation

Aviation snips with curved blades allow the cutting edge to follow a tight radius without distorting the sheet. Straight snips are intended for straight cuts and gentle curves. Bench shears cut straight lines, and a hacksaw is used for thicker sections or rods.

Question 41Materials and Hand Tools for Sheet Metal Work

What is the main purpose of a sheet metal stake in hand forming?

  1. To measure the angle of a bend
  2. To act as an anvil or former that supports the sheet during hammering Correct answer.
  3. To punch rivet holes in the sheet
  4. To clamp the sheet firmly to the bench

Explanation

Stakes are shaped steel supports that act as small anvils or formers. The sheet is held against the stake and hammered so the metal takes the stake's shape. They do not clamp, measure angles or punch holes.

Question 42Materials and Hand Tools for Sheet Metal Work

A rivet joint in a duct is failing because the rivet holes were drilled oversize. What is the most appropriate corrective action?

  1. Use a larger rivet in the same hole
  2. Reduce the rivet pitch and add more oversize rivets
  3. Hammer the rivet head flatter to spread it
  4. Weld the hole closed and redrill to the correct size Correct answer.

Explanation

Oversize holes reduce the bearing area and allow the joint to work loose, so the correct repair is to restore the hole to the specified size, for example by welding and redrilling or by using a suitable repair bush. Using a larger rivet changes the specified joint and may not fit the parts. Adding more oversize rivets does not restore the fit.

Question 43Materials and Hand Tools for Sheet Metal Work

Which tool is used to check that two adjacent faces of a folded sheet metal box are at exactly 90 degrees?

  1. Inside caliper
  2. Micrometer
  3. Engineer's try square Correct answer.
  4. Vernier depth gauge

Explanation

An engineer's try square has a hardened blade set at exactly 90 degrees to the stock and is used to check squareness of folded corners. Calipers measure internal or external sizes, a depth gauge measures depth, and a micrometer measures thickness or diameter.

Question 44Materials and Hand Tools for Sheet Metal Work

What is the effect of work hardening on a sheet metal that has been hammered and bent repeatedly?

  1. It becomes harder and less ductile Correct answer.
  2. It becomes lighter in weight
  3. It becomes non-magnetic
  4. It becomes softer and more ductile

Explanation

Repeated plastic deformation distorts the crystal lattice and increases dislocation density, making the metal harder and stronger but less ductile. This is work hardening, and it is why annealed sheet is used when severe forming is required. Weight and magnetic properties are not changed by work hardening.

Question 45Materials and Hand Tools for Sheet Metal Work

A tinner's snip leaves a burr on the cut edge of a sheet. Which operation removes this burr safely?

  1. Bending the edge back and forth until it breaks
  2. Filing along the edge with a smooth file Correct answer.
  3. Hammering the edge flat on the bench
  4. Grinding the edge with the sheet held by hand

Explanation

A smooth file drawn along the edge removes the sharp burr and produces a safe, clean edge. The sheet should be supported and the file used away from the body. Hammering flattens but does not remove the burr, and grinding or bending an unsupported thin edge is unsafe.

Question 46Materials and Hand Tools for Sheet Metal Work

Which of the following best describes the difference between a punch and a die in a sheet metal press tool?

  1. The punch and die are identical and interchangeable parts
  2. The punch holds the sheet while the die cuts it
  3. The punch is the lower member and the die is the upper member
  4. The punch is the male member that enters the die, which is the female member Correct answer.

Explanation

In a press tool the punch is the male component that is forced into the die opening, which is the female component. The clearance between them controls the shearing action. They are not interchangeable, and their vertical positions depend on the press design rather than their function.

Question 47Materials and Hand Tools for Sheet Metal Work

During bending, a sheet develops a crack on the outside of the bend while the inside shows no defect. Which change to the process is most likely to prevent the crack?

  1. Use a sharper punch nose with zero clearance
  2. Increase the bending speed sharply
  3. Increase the bend radius and orient the bend across the grain Correct answer.
  4. Reduce the bend radius further

Explanation

Cracking on the outside of a bend is caused by excessive tensile strain on the outer fibres. Increasing the bend radius reduces that strain, and bending across the rolling grain direction improves ductility in the bend. A sharper punch or a smaller radius increases strain and worsens the problem.

Question 48Materials and Hand Tools for Sheet Metal Work

A mild steel sheet and an aluminium sheet of the same thickness are compared for springback after identical bending. Which statement is correct?

  1. Aluminium shows more springback because of its lower modulus of elasticity Correct answer.
  2. Mild steel shows more springback because it is denser
  3. Springback depends only on the bend angle and not on the material
  4. Both show identical springback because thickness is the same

Explanation

Springback is proportional to the elastic recovery, which is greater when the elastic modulus is lower. Aluminium has a lower modulus than steel, so it springs back more for the same bend geometry. Thickness alone does not fix springback, and the material's modulus and yield strength both matter.

Question 49Materials and Hand Tools for Sheet Metal Work

A layout is to be transferred from a developed pattern to a sheet using a prick punch and then a centre punch. Why is the prick punch used first?

  1. To make a deep hole for the rivet
  2. To harden the surface of the sheet
  3. To mark the position lightly so it can be checked before enlarging Correct answer.
  4. To remove the layout dye from the area

Explanation

A prick punch makes a small, shallow mark that can be checked against the drawing and adjusted if necessary. Once the position is confirmed, a centre punch enlarges the mark to guide a drill. The prick punch does not drill, harden or clean the surface.

Question 50Materials and Hand Tools for Sheet Metal Work

A fabricated duct shows a leak along a folded seam after pressure testing. Inspection shows the seam was set with insufficient overlap and no locking. Which corrective measure best ensures a leak-tight joint?

  1. Re-form the seam with the specified overlap and a proper lock, then seal as specified Correct answer.
  2. Reduce the test pressure so the leak is not detected
  3. Apply more solder over the outside of the seam only
  4. Increase the rivet spacing along the seam

Explanation

A leak-tight folded seam depends on the specified overlap and a correctly formed lock that grips the sheets together. Re-forming the seam to the drawing restores the mechanical seal, and any specified sealant can then be applied. External solder alone does not compensate for a poor mechanical joint, and reducing test pressure or changing rivet spacing does not correct the seam.