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Maharashtra HSC Mechanical Technology (Vocational) study materials
Maharashtra HSC Mechanical Technology (Vocational) study resources

Maharashtra HSC Mechanical Technology (Vocational) practice questions

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Question 1Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a centre lathe, the tailstock is mainly used to

  1. support the free end of a long workpiece with a centre Correct answer.
  2. move the carriage along the bed automatically
  3. grip the workpiece and rotate it under power
  4. hold the tool in position during facing

Explanation

The tailstock supports the far end of a slender workpiece, often through a dead centre, and it can also hold drills for axial operations. It does not drive the work; that is the function of the headstock.

Question 2Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

In climb (down) milling, the cutter tooth at the point of contact moves

  1. at right angles to the workpiece feed
  2. opposite to the workpiece feed direction
  3. only during the return stroke of the table
  4. in the same direction as the workpiece feed Correct answer.

Explanation

In climb milling the cutter rotates so that its teeth travel in the same direction as the feed at the contact point. This gives a thinner chip at entry and can improve finish on backlash-free machines.

Question 3Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The standard point angle of a general-purpose twist drill for drilling mild steel is

  1. 135°
  2. 90°
  3. 60°
  4. 118° Correct answer.

Explanation

A 118° included point angle is the common general-purpose drill geometry for mild steel and many other materials. Flatter points such as 135° are used for harder or thinner work.

Question 4Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The quick-return mechanism of a shaping machine is provided to

  1. hold the clapper box firmly during cutting
  2. give automatic cross-feed to the table
  3. reduce the time taken by the return stroke Correct answer.
  4. increase the cutting speed during the forward stroke

Explanation

A shaping machine cuts only on the forward stroke, so the return stroke is made faster to save non-cutting time. The quick-return mechanism achieves this by using a slotted link and crank arrangement.

Question 5Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

For grinding a mild steel workpiece, the usual abrasive in the grinding wheel is

  1. silicon carbide
  2. diamond
  3. aluminium oxide Correct answer.
  4. cubic boron nitride

Explanation

Aluminium oxide abrasive is tough and suitable for grinding ferrous materials such as mild steel. Silicon carbide is generally chosen for non-ferrous metals and some cast irons, while diamond and CBN are for very hard or specialised work.

Question 6Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

When a taper is turned with the compound rest of a lathe, the compound rest is swivelled through

  1. half the included angle of the taper Correct answer.
  2. the full included angle of the taper
  3. 90° minus the included angle of the taper
  4. twice the included angle of the taper

Explanation

The compound rest is set to half the included angle because the tool moves along one side of the taper. The included angle is measured across the full cone, so the swivel angle is half of it.

Question 7Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A dividing head with a 40:1 worm ratio is used to mill 12 equally spaced teeth. The indexing crank movement for each tooth is

  1. 3 turns and 8 holes on a 39-hole circle
  2. 4 turns and 13 holes on a 39-hole circle
  3. 3 turns and 13 holes on a 39-hole circle Correct answer.
  4. 3 turns and 13 holes on a 24-hole circle

Explanation

For simple indexing, crank turns = 40/N = 40/12 = 3 1/3. A third of a turn equals 13 holes on a 39-hole circle, so the setting is 3 turns plus 13 holes.

Question 8Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

Reaming a drilled hole is mainly done to

  1. locate the hole accurately for drilling
  2. produce an internal thread in the hole
  3. increase the hole diameter by a large amount
  4. improve the dimensional accuracy and surface finish Correct answer.

Explanation

Reaming removes a small amount of material to bring a drilled hole closer to size and to improve its finish and straightness. It is not a bulk material removal operation and does not cut threads.

Question 9Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a mechanical shaping machine, the length of the ram stroke is adjusted by

  1. changing the radial position of the crank pin Correct answer.
  2. adjusting the cross-slide feed ratchet
  3. changing the position of the clapper box
  4. moving the tool post along the ram

Explanation

The stroke length depends on the crank radius, so moving the crank pin radially in the crank disc changes it. The ram and tool positions are then set so the tool clears the work at both ends.

Question 10Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The operation of sharpening a glazed or blunt grinding wheel by removing the dulled abrasive layer is called

  1. balancing
  2. truing
  3. dressing Correct answer.
  4. loading

Explanation

Dressing removes the glazed or worn outer layer so fresh abrasive grains can cut efficiently. Truing, by contrast, restores the geometric shape of the wheel.

Question 11Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a centre lathe, the lead screw is engaged to the carriage mainly when

  1. turning long cylindrical surfaces with automatic feed
  2. rotating the tailstock handwheel for centre drilling
  3. cutting screw threads with the half-nut engaged Correct answer.
  4. adjusting the compound rest swivel angle

Explanation

The lead screw is used with the half-nut to move the carriage in exact relation to spindle rotation, which is necessary for cutting screw threads. Ordinary longitudinal turning uses the feed rod, while the tailstock and compound rest have separate manual functions.

Question 12Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The flutes of a standard twist drill are provided mainly to

  1. increase the shank diameter for gripping
  2. allow chips to escape and form the cutting edges Correct answer.
  3. reduce the point angle during regrinding
  4. supply coolant directly to the drill point

Explanation

The flutes form the cutting edges along the drill body and provide a helical passage that lifts chips out of the hole. Coolant may flow along the flutes, but chip removal and edge formation are their primary purposes.

Question 13Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The clapper box on a shaping machine is used to

  1. increase the ram stroke length
  2. change the quick-return ratio
  3. lift the tool clear of the work during the return stroke Correct answer.
  4. hold the workpiece on the table

Explanation

The clapper box hinges so the tool lifts slightly on the return stroke, preventing the cutting edge from rubbing on the workpiece. This reduces tool wear and avoids dragging marks on the machined surface.

Question 14Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A mild steel bar of 40 mm diameter is turned on a centre lathe at a cutting speed of 30 m/min. The spindle speed nearest to the correct value is

  1. 480 rpm
  2. 120 rpm
  3. 240 rpm Correct answer.
  4. 750 rpm

Explanation

The spindle speed is calculated from N = 1000V/(πD), where V is cutting speed in m/min and D is diameter in mm. Substituting V = 30 m/min and D = 40 mm gives about 239 rpm, so 240 rpm is the nearest choice.

Question 15Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A slab milling cutter has 8 teeth and rotates at 120 rpm. If the table feed is 60 mm/min, the feed per tooth is

  1. 0.250 mm/tooth
  2. 0.0625 mm/tooth Correct answer.
  3. 0.500 mm/tooth
  4. 0.125 mm/tooth

Explanation

Table feed per revolution equals feed rate divided by cutter speed: 60/120 = 0.5 mm/rev. Dividing by the 8 teeth gives 0.5/8 = 0.0625 mm/tooth.

Question 16Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

In a grinding wheel marking, the grade letter indicates the

  1. abrasive grain size
  2. strength of the bond holding the abrasive grains Correct answer.
  3. maximum wheel peripheral speed
  4. type of abrasive material

Explanation

In a standard grinding wheel marking, the letter grade indicates the strength of the bond or the amount of bond holding the abrasive grains. Soft grades release dull grains easily, while hard grades retain them longer.

Question 17Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A pilot hole is drilled before a large-diameter twist drill mainly to

  1. improve hole location and reduce thrust force Correct answer.
  2. eliminate the need for a drill bushing
  3. produce a mirror finish in the hole
  4. increase the drill point angle

Explanation

A pilot hole establishes the drill axis and removes a small central core, which reduces the thrust needed by a large drill and improves hole location. It does not finish the hole; that may require boring or reaming.

Question 18Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a shaping machine, the cutting stroke takes 1.2 s and the return stroke takes 0.8 s. The quick-return ratio, stated as cutting time : return time, is

  1. 2.00
  2. 1.50 Correct answer.
  3. 0.67
  4. 1.20

Explanation

The quick-return ratio is the cutting-stroke time divided by the return-stroke time, so 1.2/0.8 = 1.5. A ratio greater than one shows that the return stroke is faster than the cutting stroke.

Question 19Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A lathe has a lead screw of 6 mm pitch. For cutting a metric thread of 2.0 mm pitch, the number of spindle revolutions to one revolution of the lead screw must be

  1. 2:1
  2. 1:2
  3. 1:3
  4. 3:1 Correct answer.

Explanation

One spindle revolution must advance the carriage by one thread pitch, 2.0 mm. Since the lead screw advances 6 mm per revolution, it must turn 2/6 = 1/3 revolution per spindle revolution, giving 3 spindle revolutions per lead screw revolution.

Question 20Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A 20 mm diameter hole is drilled through a 30 mm thick plate at a cutting speed of 25 m/min and a feed of 0.2 mm/rev. The drilling time, ignoring approach and overtravel, is nearest to

  1. 60.0 s
  2. 11.3 s
  3. 22.6 s Correct answer.
  4. 45.2 s

Explanation

Spindle speed is N = 1000 × 25/(π × 20) ≈ 398 rpm, and feed rate is 0.2 × 398 ≈ 79.6 mm/min. Drilling time for 30 mm travel is 30/79.6 ≈ 0.377 min, or about 22.6 s, ignoring approach and overtravel.

Question 21Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

In a drilling machine, the Morse taper on the shank of a large twist drill is provided mainly to

  1. allow the drill to be changed while the spindle is rotating
  2. carry coolant directly to the cutting edges
  3. drive the drill and centre it in the spindle socket Correct answer.
  4. reduce the shank diameter so that the drill can pass through the hole

Explanation

The Morse taper is a self-holding taper: friction between the shank and the spindle socket drives the drill and keeps it centred. A drift is used to release it, but the drill is not changed while the spindle rotates.

Question 22Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The swivel base provided under a machine vice on a milling machine allows the workpiece to be

  1. moved longitudinally by hand during the cutting stroke
  2. tilted about a horizontal axis for angular milling
  3. clamped above the table surface without using clamps
  4. rotated about a vertical axis to a required angle Correct answer.

Explanation

A swivel-base vice has graduations and can be rotated about a vertical axis so that the workpiece is presented at an angle to the cutter. Tilting about a horizontal axis needs a tilting or universal vice.

Question 23Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The grinding operation in which a cylindrical workpiece is rotated between centres and a rotating grinding wheel is fed radially is called

  1. cylindrical grinding Correct answer.
  2. internal grinding
  3. surface grinding
  4. creep-feed grinding

Explanation

In cylindrical grinding, the workpiece rotates between centres while the grinding wheel rotates and is fed radially or axially. The result is an accurate cylindrical surface.

Question 24Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

Counterboring a drilled hole is carried out mainly to

  1. improve the alignment of a drilled hole before reaming
  2. reduce the hole diameter by squeezing metal inward
  3. form a flat seat for a socket-head screw Correct answer.
  4. cut an internal thread in a single operation

Explanation

A counterbore has a pilot that follows the drilled hole and a flat cutting end, producing a flat seat for a socket-head screw. It is not a reaming or threading operation.

Question 25Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

The thread-chasing dial on a centre lathe is used to

  1. engage the half-nut at the correct instant Correct answer.
  2. measure the pitch of an existing thread on the workpiece
  3. set the spindle speed for thread cutting
  4. lock the carriage during parting off

Explanation

The thread-chasing dial is geared to the lead screw and shows the positions at which the half-nut may be closed so that the tool enters the same thread groove on each pass. This is needed when the carriage is returned for the next cut.

Question 26Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A side and face milling cutter is particularly suitable for

  1. milling a flat surface at right angles to the spindle
  2. cutting slots and straddling two parallel faces Correct answer.
  3. drilling holes on a milling machine
  4. finishing curved profiles with a ball-nose cutter

Explanation

A side and face cutter has teeth on the periphery and on both side faces, so it can cut a slot and simultaneously machine two parallel faces in straddle milling. It is not intended for drilling or ball-nose profiling.

Question 27Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a mechanical shaping machine, the automatic table feed is applied during the

  1. cutting stroke, so that the tool produces a spiral path across the work
  2. return stroke, with the tool clear of the work Correct answer.
  3. pause at each end of the stroke
  4. whole stroke at a constant rate

Explanation

In a mechanical shaper the table cross-feed is driven by a ratchet and pawl that act during the return stroke, when the tool is clear of the work. Feeding during cutting would leave a stepped or damaged surface.

Question 28Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A lathe faceplate is preferred to a three-jaw chuck when the workpiece is

  1. too long to be held without a tailstock
  2. irregular in shape and must be clamped individually Correct answer.
  3. made of hardened steel that cannot be gripped
  4. a small cylindrical bar that needs quick centring

Explanation

A faceplate has radial slots and a plain face, so irregular castings or large workpieces can be bolted and independently balanced. A three-jaw chuck is for quickly centring regular cylindrical work.

Question 29Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A single-point carbide tool used for rough machining hardened steel is often given a negative rake angle mainly to

  1. allow the tool to be used without a tool holder
  2. strengthen the cutting edge under heavy or interrupted loads Correct answer.
  3. increase the clearance angle at the flank
  4. reduce the cutting force and the built-up edge

Explanation

A negative rake angle places more tool material behind the cutting edge, giving it greater strength under heavy or interrupted loads. The penalty is higher cutting force, so it is suited to robust carbide tools and tough conditions.

Question 30Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

Web thinning on a twist drill is carried out mainly to

  1. increase the diameter of the drill near the shank
  2. provide more space for chip removal along the flutes
  3. shorten the chisel edge and reduce thrust at the point Correct answer.
  4. change the helix angle for drilling aluminium

Explanation

Repeated point grinding increases the web thickness and lengthens the chisel edge, which raises thrust and makes the drill wander. Web thinning removes material near the point to shorten the chisel edge and restore centring.

Question 31Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a centre lathe, the tailstock is deliberately set over to turn

  1. a diamond knurl on a small handle
  2. a taper on a workpiece held between centres Correct answer.
  3. a flat face on a short cast-iron disc held in the chuck
  4. a metric screw thread using the lead screw and change gears

Explanation

Setting over the tailstock offsets the two centres, so the workpiece axis becomes inclined to the lathe bed axis. As the carriage feeds the tool parallel to the bed, this inclination generates a taper along the workpiece.

Question 32Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

Compared with up milling, down milling is characterised by

  1. the cutter and table feed moving in the same direction at the cut Correct answer.
  2. the table feed being obtained from the rapid-traverse motor
  3. the cutter being mounted on a stub arbor instead of a long arbor
  4. the cutter rotating against the table feed and the chip thickening from zero

Explanation

In down milling the cutter edge moves in the same direction as the table feed at the point of contact. The chip therefore starts at maximum thickness and decreases to zero, which tends to pull the workpiece towards the cutter and requires a backlash-free table.

Question 33Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A 20 mm diameter hole is to be finished by reaming after drilling. Using a usual reaming allowance of about 0.1 mm per side, the twist drill diameter should be

  1. 20.2 mm
  2. 20.0 mm
  3. 18.0 mm
  4. 19.8 mm Correct answer.

Explanation

Reaming is a sizing and finishing operation that removes only a small layer of material from the drilled hole. The drill diameter is therefore the finished diameter minus twice the allowance per side: 20 - 2(0.1) = 19.8 mm.

Question 34Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A surface grinding wheel is marked A 46 K 5 V. In this marking, the number 46 indicates

  1. the abrasive grain size Correct answer.
  2. the maximum safe peripheral speed
  3. the wheel diameter in millimetres
  4. the bond material and its strength

Explanation

In the standard wheel marking, the letter A denotes the abrasive type, 46 denotes the grit or grain size, K denotes the grade, 5 denotes the structure, and V denotes the vitrified bond. The number 46 therefore refers to the abrasive grain size.

Question 35Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

A 40:1 dividing head is used on a milling machine to cut 28 equally spaced flutes. Using simple indexing with a Brown & Sharpe index plate, the index crank movement per flute is

  1. 2 turns plus 3 holes on the 21-hole circle
  2. 1 turn plus 11 holes on the 21-hole circle
  3. 1 turn plus 7 holes on the 21-hole circle
  4. 1 turn plus 9 holes on the 21-hole circle Correct answer.

Explanation

For simple indexing, the crank turns per division equal 40 divided by the number of divisions: 40/28 = 1 3/7. Since 3/7 is equivalent to 9/21, the setting is one full turn plus nine holes on the 21-hole circle.

Question 36Machining and Machine Tools (lathe, milling, drilling, shaping, grinding)

On a crank-and-slotted-link shaping machine, the length of the ram stroke is changed by

  1. adjusting the swivel angle of the tool head
  2. changing the position of the clapper box on the ram
  3. changing the number of teeth in the bull gear
  4. moving the crank pin radially in the crank disc Correct answer.

Explanation

The stroke length depends on the radius of the crank pin. Moving the crank pin radially outward increases the crank radius and hence the ram travel, while moving it inward shortens the stroke.

Question 37Engineering Drawing and Computer-Aided Drafting

In a mechanical engineering drawing, which line style is specified for representing hidden edges and contours?

  1. Dashed narrow line Correct answer.
  2. Chain thin line
  3. Continuous wavy line
  4. Continuous thick line

Explanation

Hidden edges and contours are shown by short dashes of narrow line thickness so that they are clearly distinguished from visible outlines. The dashes should meet at corners and should not be used where a hidden feature coincides with a centre line. This convention follows standard drawing practice such as IS 10714 / SP 46.

Question 38Engineering Drawing and Computer-Aided Drafting

What is the standard trimmed size of an A3 drawing sheet used for vocational drawing work?

  1. 210 mm × 148 mm
  2. 420 mm × 297 mm Correct answer.
  3. 297 mm × 210 mm
  4. 594 mm × 420 mm

Explanation

The A-series is based on halving the area at each step, so an A3 sheet measures 420 mm × 297 mm. A4 is 297 mm × 210 mm and A2 is 594 mm × 420 mm. The trimmed size is the final sheet size after cutting, before any folding margin is considered.

Question 39Engineering Drawing and Computer-Aided Drafting

In CAD software, which drafting aid constrains the cursor to move only along the horizontal or vertical axis?

  1. Polar tracking
  2. Grid snap (SNAP)
  3. Object snap (OSNAP)
  4. Ortho mode Correct answer.

Explanation

Ortho mode locks cursor movement to directions parallel to the horizontal and vertical axes of the current coordinate system. It is useful for drawing straight horizontal and vertical lines without accidental slant. Polar tracking differs because it allows movement at preset angles other than 90°.

Question 40Engineering Drawing and Computer-Aided Drafting

In first-angle orthographic projection, where is the top view placed relative to the front view?

  1. To the right of the front view
  2. Above 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 projection plane, so the top view is projected below the front view. The left-side view is projected on the right of the front view. Third-angle projection reverses these positions.

Question 41Engineering Drawing and Computer-Aided Drafting

Which symbol is placed immediately before a dimension value to indicate a diameter in a mechanical drawing?

  1. Ø Correct answer.
  2. □
  3. R
  4. SR

Explanation

The symbol Ø identifies a diameter dimension, for example Ø25 means a diameter of 25 mm. The letter R denotes a radius and SR denotes a spherical radius. A square symbol is used for square sections or square features.

Question 42Engineering Drawing and Computer-Aided Drafting

In a sectional view, hatching lines representing a cut surface are normally drawn as:

  1. Dashed lines at 30° to the cutting-plane line
  2. Thick continuous lines at 45° to the outline
  3. Thin chain lines parallel to the section plane
  4. Thin continuous lines at 45° to the principal axis Correct answer.

Explanation

Cut surfaces are indicated by evenly spaced thin continuous hatching lines, usually at 45° to the principal axis or outline of the part. Different adjacent parts are hatched at different angles or spacings so the parts remain distinguishable. Thick lines and dashed lines are not used for section hatching.

Question 43Engineering Drawing and Computer-Aided Drafting

In the hole-basis system of limits and fits, the fit designated H7/g6 is a:

  1. Line fit
  2. Clearance fit Correct answer.
  3. Interference fit
  4. Transition fit

Explanation

In the hole-basis system the hole H has its lower deviation at zero, and the shaft g has a negative upper deviation. The shaft is therefore always smaller than the hole, giving a clearance fit. Interference fits use shaft letters such as p, s or u, while transition fits use letters such as j, k or n.

Question 44Engineering Drawing and Computer-Aided Drafting

Which file format is the native drawing file format of AutoCAD?

  1. DXF
  2. PDF
  3. STEP
  4. DWG Correct answer.

Explanation

DWG is the native file format in which AutoCAD saves its drawings, including layers, blocks and dimension styles. DXF is a drawing exchange format used to transfer data between different CAD programs. STEP and PDF are exchange and plotting formats rather than native AutoCAD drawing files.

Question 45Engineering Drawing and Computer-Aided Drafting

When an isometric drawing is constructed using the true isometric scale, a line of 100 mm true length is drawn at approximately what length?

  1. 100 mm
  2. 122.5 mm
  3. 70.7 mm
  4. 81.6 mm Correct answer.

Explanation

True isometric projection foreshortens all three axes by the factor cos 35.26°, which is about 0.816. A 100 mm true length therefore appears as about 81.6 mm on the isometric scale. In ordinary isometric drawing practice, full scale is used along the axes instead of the true isometric scale.

Question 46Engineering Drawing and Computer-Aided Drafting

A surface roughness symbol on a drawing specifies Ra 3.2. What does this indicate?

  1. Maximum waviness height of 3.2 mm
  2. The total tolerance band is 3.2 µm
  3. The arithmetic mean roughness value is 3.2 µm Correct answer.
  4. The minimum machining allowance is 3.2 mm

Explanation

Ra is the arithmetic mean deviation of the assessed surface profile, and its value is expressed in micrometres. Ra 3.2 therefore means an arithmetic mean roughness of 3.2 µm for the finished surface. It is a roughness parameter, not a tolerance band, waviness height or machining allowance.

Question 47Engineering Drawing and Computer-Aided Drafting

In orthographic projection, the view obtained by projecting an object onto the vertical plane is called the:

  1. front view Correct answer.
  2. side view
  3. top view
  4. bottom view

Explanation

The vertical plane receives the front view in orthographic projection. The top view is projected onto the horizontal plane, while side views are projected onto profile planes.

Question 48Engineering Drawing and Computer-Aided Drafting

In CAD drafting, which command creates a duplicate of selected geometry at a specified displacement without removing the original?

  1. COPY Correct answer.
  2. TRIM
  3. MOVE
  4. ROTATE

Explanation

COPY duplicates selected objects at a displacement and leaves the originals in place. MOVE changes the position of the original objects instead of creating a duplicate.

Question 49Engineering Drawing and Computer-Aided Drafting

A centre line in a mechanical drawing is drawn to show:

  1. axes of symmetry and centres of circles Correct answer.
  2. hidden edges and contours
  3. visible outlines of the object
  4. the path of a cutting plane

Explanation

Centre lines are thin chain lines used to mark axes of symmetry, centres of circles and pitch circles. They are not used for visible outlines or hidden edges.

Question 50Engineering Drawing and Computer-Aided Drafting

A shaft dimension is written as 40 ±0.05 mm. The total tolerance on the shaft diameter is:

  1. 0.05 mm
  2. 0.10 mm Correct answer.
  3. 0.025 mm
  4. 40.05 mm

Explanation

The tolerance is the difference between the upper and lower limits. With ±0.05 mm, the upper limit is 40.05 mm and the lower limit is 39.95 mm, giving a zone width of 0.10 mm.