Abrasive Wheels Training Certificate Inspection and Storage 2 — Questions and Answers
Question 1: Why must abrasive wheels be protected from frost during storage?
- Frost changes the colour of the wheel
- Water absorbed into the wheel can freeze and expand, causing internal cracks (Correct answer)
- Frost makes the wheel too hard to use
- Frost has no effect on abrasive wheels
Correct answer: Water absorbed into the wheel can freeze and expand, causing internal cracks
Moisture that has been absorbed into an abrasive wheel (particularly resinoid-bonded wheels) can freeze and expand during cold conditions. This expansion creates internal micro-cracks that weaken the wheel structure and can lead to catastrophic failure during operation.
Question 2: What should an operator do if they discover a crack in an abrasive wheel during a pre-use inspection?
- Use adhesive to repair the crack and continue
- Immediately remove the wheel from service and destroy it to prevent reuse, then report the finding (Correct answer)
- Continue using the wheel but at reduced speed
- Turn the wheel around so the crack is on the back
Correct answer: Immediately remove the wheel from service and destroy it to prevent reuse, then report the finding
A cracked abrasive wheel must never be used. It should be immediately removed from the machine and destroyed (broken up) to ensure it cannot be inadvertently refitted. The finding should be reported to the supervisor. A cracked wheel can disintegrate at operating speed with lethal consequences.
Question 3: What is the purpose of 'dressing' an abrasive wheel?
- To paint the wheel for identification purposes
- To restore the cutting face by removing glazed or loaded material and truing the wheel surface (Correct answer)
- To wrap the wheel in protective material for storage
- To increase the wheel's maximum operating speed
Correct answer: To restore the cutting face by removing glazed or loaded material and truing the wheel surface
Dressing an abrasive wheel removes glazed, loaded (clogged), or unevenly worn material from the cutting surface and restores its true round shape. This is done using a dressing tool (typically a diamond or star-type dresser). Regular dressing improves cutting efficiency and reduces vibration.
Question 4: How should large vitrified abrasive wheels be stored?
- Stacked flat, one on top of another
- Stored on edge in suitable racks, supported to prevent rolling (Correct answer)
- Leaned against the workshop wall
- Suspended from the ceiling by rope through the bore
Correct answer: Stored on edge in suitable racks, supported to prevent rolling
Large vitrified wheels should be stored on edge in suitable racks with supports to prevent them from rolling. Stacking flat can cause the bottom wheels to crack under the weight of those above. Small wheels can be stored flat with separators between them.
Question 5: What is 'glazing' of an abrasive wheel and why is it a problem?
- It means the wheel has a shiny protective coating applied at the factory
- The abrasive grains become worn flat and smooth, reducing cutting ability and increasing heat and friction (Correct answer)
- It means the wheel has been treated with a waterproof glaze
- Glazing only occurs with diamond wheels
Correct answer: The abrasive grains become worn flat and smooth, reducing cutting ability and increasing heat and friction
Glazing occurs when the abrasive grains become worn flat and smooth rather than fracturing to expose fresh cutting edges. This reduces cutting efficiency, increases friction and heat generation, and can cause workpiece burning. A glazed wheel needs to be dressed to restore its cutting ability.
Question 6: According to PUWER 1998, how often must work equipment including abrasive wheel machines be inspected?
- Only once when first purchased
- At suitable intervals and each time exceptional circumstances occur that may affect safety (Correct answer)
- Every 5 years by the manufacturer
- Inspection is voluntary under PUWER
Correct answer: At suitable intervals and each time exceptional circumstances occur that may affect safety
PUWER 1998, Regulation 6 requires that work equipment is inspected at suitable intervals and each time exceptional circumstances (such as modifications, accidents, or long periods out of use) occur that could jeopardise safety. Records of inspections must be kept.
Abrasive Wheels Training Certificate Inspection and Storage 2
Why must abrasive wheels be protected from frost during storage?