SI Practice Test 5: Tools, Joining and Materials

Answer: D

Correct answer: Spirit level. Plumb means truly vertical. A spirit level placed against the post shows plumb when the bubble in its vertical vial is centered between the marks.

• A: A try square checks a 90-degree angle between two surfaces, not whether a post is vertical.
• B: A marking gauge scribes a line parallel to an edge; it cannot sense vertical.
• C: Dividers transfer distances or scribe arcs and give no information about plumb.
• D (correct): Its bubble vials show level (horizontal) or plumb (vertical) when the bubble is centered.

Answer: A

Correct answer: A welding helmet with a suitable filter shade. An exposed welding arc can injure the eyes and skin. Use a welding helmet or screen with a filter shade suited to the operation; ordinary safety glasses do not provide that filtering.

• A (correct): Arc radiation requires a proper filter lens; a helmet with the right shade provides it.
• B: Side shields stop flying particles from the side but do not filter intense arc radiation.
• C: Polarized sunglasses reduce glare but are not rated filters for welding arc radiation.
• D: A dust mask addresses breathing, not eye exposure to arc light.

Answer: C

Correct answer: Metric thread pitch in millimeters. In a metric thread callout, M means ISO metric thread, the first number is the nominal major diameter in millimeters, and the number after × is the pitch, the axial distance from one thread crest to the next. So M8 × 1.25 is an 8 mm thread with crests 1.25 mm apart, the standard coarse pitch for that size. The tempting misreading carries over inch habits, where the second number is a thread count; metric callouts give the distance between threads instead.

• A: An M thread is metric and the value is the pitch here, not shaft length.
• B: Torque requirements are specified separately from the ordinary thread pitch notation.
• C (correct): The notation indicates adjacent-thread axial pitch of 1.25 mm for this metric callout.
• D: The nominal major diameter is approximately 8 mm and 1.25 is not a thread count.

Answer: B

Correct answer: 200 GPa. Young's modulus E is the slope of the elastic part of the stress-strain curve: E = stress ÷ strain. Since strain has no units, E carries the units of stress: 80 MPa ÷ 0.0004 = 200,000 MPa, and dividing by 1,000 converts that to 200 GPa. This value is typical of steel, which makes a good sanity check. A frequent mistake is multiplying stress by strain; a stiff material needs a large stress to produce a tiny strain, so E must be far larger than the stress.

• A: Dividing strain by stress inverts the required modulus relation.
• B (correct): 80 MPa divided by 0.0004 is 200,000 MPa, or 200 GPa.
• C: This mistakes the given stress magnitude for the much larger modulus.
• D: Multiplying stress by strain does not produce the elastic modulus.

Answer: B

Correct answer: The size of the bolt head or nut it fits. A socket has two separate sizes. The drive size (3/8 in) is the square hole for the ratchet or extension, while the opening size (17 mm) is the hex head it fits; the two numbers are unrelated.

• A: That is the drive size, which here is the 3/8 in marking, not the 17 mm marking.
• B (correct): The opening size names the fastener the socket fits, here a 17 mm hex head.
• C: Drive size is a separate square-hole measurement; the 17 mm figure is unrelated to the handle.
• D: Socket markings for size describe the opening, not the overall length of the socket.

Answer: B

Correct answer: 1/8 inch. The work rest supports the piece being ground. If the gap between the rest and the wheel is too wide, the work can be pulled down and wedged between them, which can jam the wheel, break it, or drag fingers in. OSHA therefore limits the work-rest opening on offhand grinders to 1/8 inch, and the gap must be readjusted as the wheel wears. The common confusion is the 1/4-inch limit, which applies to the upper tongue guard, not the rest.

• A: Half an inch is well above the specified work-rest maximum.
• B (correct): 29 CFR 1910.215(a)(4) sets a maximum one-eighth-inch work-rest opening for the covered offhand machines.
• C: One quarter inch relates to the distinct adjustable upper tongue opening in covered machines.
• D: Such an opening exceeds the applicable work-rest limit and increases jamming risk.

Answer: C

Correct answer: Center punch. A center punch has a hardened, conical point. Struck once with a hammer, it leaves a small dimple that keeps a drill bit from wandering across smooth metal as drilling begins. Layout lines are usually scribed first, and the punch marks their intersection. The tempting confusion is the pin punch, which has a flat, straight tip for driving pins out of holes and cannot make a pointed mark. A file removes material over an area rather than marking a point.

• A: A pipe wrench grips round pipe.
• B: A pin punch drives an existing pin rather than making a point.
• C (correct): The pointed center punch establishes a drill-start location.
• D: A file shapes material over an area.

Answer: B

Correct answer: Mechanical retention against full nut rotation. A castle nut has slots cut across its top, and the stud has a drilled cross hole. When a slot lines up with the hole, a cotter pin passes through both and is bent over, so the nut cannot turn off even if it loosens slightly. This positive locking is common on axle and steering components. The pin does not set or indicate preload; correct torque is applied first, then the nut is aligned to the next slot.

• A: It retains a nut rather than changing thread geometry.
• B (correct): The pin physically blocks rotation of a suitably slotted nut in a designed assembly.
• C: The pin prevents a defined rotation path but cannot indicate the axial tension or clamping force in the bolt.
• D: A cotter pin is a thin split pin with no broad bearing surface, so it cannot spread load the way a washer does.

Answer: A

Correct answer: 1.70 mm. Value of one division = 0.5 mm / 50 = 0.01 mm.

• A (correct): Each division is 0.5 / 50 = 0.01 mm, so 3(0.5) + 20(0.01) = 1.50 + 0.20 = 1.70 mm.
• B: This takes each division as 0.001 mm instead of 0.5 / 50 = 0.01 mm.
• C: This assumes 1 mm per revolution, ignoring the stated 0.5 mm advance.
• D: This takes each division as 0.005 mm, dividing the 0.5 mm pitch by 100 instead of by the 50 divisions.

Answer: D

Correct answer: Crook. Match the defect to the direction of the curve: along the face is bow, along the edge is crook, across the width is cup, and corners out of plane is twist. Here the face is flat but the edge is curved, so the defect is crook.

• A: Bow is curvature along the face over the length; this board lies flat on its face, so it is not bowed.
• B: Cup is curvature across the width; the problem describes a curve along the length of the edge.
• C: Twist means the four corners are out of one plane; this board sits flat with its whole face on the bench.
• D (correct): Crook is curvature along the edge of a board, in the same plane as its face.