CO Core Drilling Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary function of core drilling in construction?
A. Mix concrete
B. Remove debris
C. Create precise holes in concrete
D. Paint surfaces
C. Create precise holes in concrete
Rationale: Core drilling is used to create exact cylindrical holes for
utilities, anchors, or inspection in concrete structures.
2. Which type of core bit is most effective for reinforced concrete?
A. Wood bit
B. Diamond bit
C. Masonry bit
D. Metal bit
B. Diamond bit
Rationale: Diamond bits are durable and can cut through concrete with
embedded steel reinforcement efficiently.
3. Why is water commonly used during core drilling?
A. To soften concrete
B. To clean the drill motor
C. To cool the bit and reduce dust
D. To speed up drilling
,C. To cool the bit and reduce dust
Rationale: Wet drilling prevents overheating, extends bit life, and reduces
hazardous airborne dust.
4. Which safety equipment is essential during core drilling?
A. Gloves only
B. Hard hat, eye protection, hearing protection, gloves, and steel-toed
boots
C. Apron only
D. Earplugs only
B. Hard hat, eye protection, hearing protection, gloves, and steel-toed
boots
Rationale: Core drilling involves flying debris, vibration, and noise; full
PPE is necessary to prevent injury.
5. What is the purpose of a drill stand?
A. Measure concrete thickness
B. Stabilize the drill for accurate holes
C. Store cores
D. Lubricate the bit
B. Stabilize the drill for accurate holes
Rationale: A drill stand ensures straight, precise drilling and reduces
operator fatigue.
6. What is the maximum recommended diameter for handheld core
drilling?
A. 50 mm
B. 100 mm
C. 300 mm
D. 500 mm
B. 100 mm
Rationale: Larger diameters require rigs or stands for safety and precision.
7. How can dust be controlled during dry core drilling?
A. Drill faster
, B. Use vacuum extraction
C. Only drill at night
D. Cover the hole with tape
B. Use vacuum extraction
Rationale: Vacuum systems capture dust at the source, reducing exposure
to silica particles.
8. What is the main hazard when drilling reinforced concrete?
A. Dust inhalation
B. Tripping on cables
C. Hitting rebar
D. All of the above
D. All of the above
Rationale: Reinforced concrete drilling presents multiple hazards including
debris, rebar, dust, and electrical risks.
9. How should feed pressure be applied when core drilling?
A. Excessive downward force
B. Continuous, steady pressure
C. No pressure
D. Hammering
B. Continuous, steady pressure
Rationale: Proper feed pressure prevents binding, overheating, and ensures
efficient cutting.
10. Which motor type is most suitable for large-diameter core
drilling?
A. Handheld electric
B. Hydraulic or pneumatic
C. Manual hand drill
D. Cordless screwdriver
B. Hydraulic or pneumatic
Rationale: Large-diameter core drills require high torque and continuous
power beyond handheld electric motors.
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary function of core drilling in construction?
A. Mix concrete
B. Remove debris
C. Create precise holes in concrete
D. Paint surfaces
C. Create precise holes in concrete
Rationale: Core drilling is used to create exact cylindrical holes for
utilities, anchors, or inspection in concrete structures.
2. Which type of core bit is most effective for reinforced concrete?
A. Wood bit
B. Diamond bit
C. Masonry bit
D. Metal bit
B. Diamond bit
Rationale: Diamond bits are durable and can cut through concrete with
embedded steel reinforcement efficiently.
3. Why is water commonly used during core drilling?
A. To soften concrete
B. To clean the drill motor
C. To cool the bit and reduce dust
D. To speed up drilling
,C. To cool the bit and reduce dust
Rationale: Wet drilling prevents overheating, extends bit life, and reduces
hazardous airborne dust.
4. Which safety equipment is essential during core drilling?
A. Gloves only
B. Hard hat, eye protection, hearing protection, gloves, and steel-toed
boots
C. Apron only
D. Earplugs only
B. Hard hat, eye protection, hearing protection, gloves, and steel-toed
boots
Rationale: Core drilling involves flying debris, vibration, and noise; full
PPE is necessary to prevent injury.
5. What is the purpose of a drill stand?
A. Measure concrete thickness
B. Stabilize the drill for accurate holes
C. Store cores
D. Lubricate the bit
B. Stabilize the drill for accurate holes
Rationale: A drill stand ensures straight, precise drilling and reduces
operator fatigue.
6. What is the maximum recommended diameter for handheld core
drilling?
A. 50 mm
B. 100 mm
C. 300 mm
D. 500 mm
B. 100 mm
Rationale: Larger diameters require rigs or stands for safety and precision.
7. How can dust be controlled during dry core drilling?
A. Drill faster
, B. Use vacuum extraction
C. Only drill at night
D. Cover the hole with tape
B. Use vacuum extraction
Rationale: Vacuum systems capture dust at the source, reducing exposure
to silica particles.
8. What is the main hazard when drilling reinforced concrete?
A. Dust inhalation
B. Tripping on cables
C. Hitting rebar
D. All of the above
D. All of the above
Rationale: Reinforced concrete drilling presents multiple hazards including
debris, rebar, dust, and electrical risks.
9. How should feed pressure be applied when core drilling?
A. Excessive downward force
B. Continuous, steady pressure
C. No pressure
D. Hammering
B. Continuous, steady pressure
Rationale: Proper feed pressure prevents binding, overheating, and ensures
efficient cutting.
10. Which motor type is most suitable for large-diameter core
drilling?
A. Handheld electric
B. Hydraulic or pneumatic
C. Manual hand drill
D. Cordless screwdriver
B. Hydraulic or pneumatic
Rationale: Large-diameter core drills require high torque and continuous
power beyond handheld electric motors.
