Abrasive Wheels Training Certificate Work Rest Adjustment and Operating Techniques 2 — Questions and Answers
Question 1: What is the correct stance for an operator using a bench or pedestal grinder?
- Stand directly in front of the wheel's plane of rotation
- Stand to one side, clear of the wheel's plane of rotation (Correct answer)
- Crouch below the height of the wheel centre
- Stand as far back from the machine as possible
Correct answer: Stand to one side, clear of the wheel's plane of rotation
Standing to the side of the wheel's plane of rotation means that if the wheel bursts, the fragments are less likely to strike the operator directly.
Question 2: When applying a workpiece to a rotating abrasive wheel, what is the correct pressure to use?
- Heavy and constant pressure for fastest material removal
- Light, even, and controlled pressure (Correct answer)
- Intermittent heavy bursts of pressure
- No pressure — allow the wheel's rotation to do all the work
Correct answer: Light, even, and controlled pressure
Light, even pressure ensures controlled grinding, prevents overheating of the workpiece, and reduces the risk of the wheel shattering due to sudden impact loading.
Question 3: Which surface of a straight abrasive wheel should be used for general purpose grinding on a bench grinder?
- The flat side face of the wheel
- The peripheral (outer) face of the wheel (Correct answer)
- Either the side or peripheral face depending on preference
- The inner bore surface with a suitable fixture
Correct answer: The peripheral (outer) face of the wheel
General purpose grinding must only be performed on the peripheral face; using the flat side creates lateral stresses that straight wheels are not designed to withstand, risking breakage.
Question 4: How should a workpiece be supported when grinding on a bench grinder?
- Held completely freehand without additional support
- Firmly supported on the work rest (Correct answer)
- Gripped with both hands held well away from the wheel face
- Secured in a floor-mounted vice beside the machine
Correct answer: Firmly supported on the work rest
The workpiece must be firmly supported on the work rest at all times to maintain control and prevent it from being snatched violently by the rotating wheel.
Question 5: For how long should a newly mounted abrasive wheel be run before commencing grinding work?
- No running-in period is required if the ring test was passed
- At least one minute at full operating speed with the guard in place (Correct answer)
- 30 seconds at half the rated speed
- 5 minutes at reduced speed followed by 5 minutes at full speed
Correct answer: At least one minute at full operating speed with the guard in place
A newly mounted wheel must be run for at least one minute at full operating speed with guards fitted to reveal any faults such as vibration, cracks, or imbalance before it contacts a workpiece.
Question 6: If a workpiece becomes excessively hot during grinding, what should the operator do?
- Continue grinding to complete the task as quickly as possible
- Allow the workpiece to cool naturally or apply suitable coolant (Correct answer)
- Increase grinding pressure to reduce the total grinding time
- Quench it immediately in any available liquid to hand
Correct answer: Allow the workpiece to cool naturally or apply suitable coolant
The workpiece should be allowed to cool or appropriate coolant should be applied; continuing to grind an overheated workpiece risks burning the operator and can adversely alter the material's properties.
Question 7: What does 'loading' of an abrasive wheel refer to?
- Placing a heavy workpiece on the work rest before grinding
- The wheel's pores becoming blocked with ground material, reducing cutting efficiency (Correct answer)
- Setting the machine to its maximum permitted operating speed
- Adding counterweights to balance an out-of-balance wheel
Correct answer: The wheel's pores becoming blocked with ground material, reducing cutting efficiency
Loading occurs when swarf or metal particles clog the pores between the abrasive grains, preventing the wheel from cutting effectively and causing excessive heat through friction.
Abrasive Wheels Training Certificate Work Rest Adjustment and Operating Techniques 2
What is the correct stance for an operator using a bench or pedestal grinder?