Abrasive Wheels Training Certificate Guarding Requirements — Questions and Answers
Question 1: What does PUWER 1998 Regulation 11 require regarding guards on abrasive wheel machines?
- Guards must be provided and maintained that enclose the wheel as much as possible consistent with normal operation, and must be strong enough to retain fragments in the event of wheel burst (Correct answer)
- Guards are only required for bench grinders, not portable angle grinders
- Guards may be removed during fine finishing operations
- A written risk assessment substitutes for a physical guard if justified
Correct answer: Guards must be provided and maintained that enclose the wheel as much as possible consistent with normal operation, and must be strong enough to retain fragments in the event of wheel burst
PUWER Regulation 11 requires that dangerous parts of machinery — including rotating abrasive wheels — are guarded by fixed or adjustable guards. For abrasive wheels, the guard must enclose the maximum practicable portion of the wheel, provide structural protection against wheel burst fragments, and comply with relevant British Standards.
Question 2: What is the maximum angle of exposure permitted for the grinding face of a bench grinder wheel?
- Maximum 90 degrees of wheel exposure above the work rest (the remaining arc must be enclosed by the guard) (Correct answer)
- 180 degrees — the top half may be exposed
- 360 degrees is acceptable if a transparent shield is fitted
- There is no angle limitation — only the maximum gap dimension is regulated
Correct answer: Maximum 90 degrees of wheel exposure above the work rest (the remaining arc must be enclosed by the guard)
For bench grinders, the guard must enclose the wheel except for the necessary working area. BS 4481 specifies that the grinding exposure (the arc of wheel open to the work) should not exceed 90 degrees above the horizontal plane of the work rest. This minimises the arc of wheel exposed to the operator.
Question 3: What is the maximum permitted angle of wheel exposure for a portable angle grinder guard?
- 180 degrees — the guard must cover at least the upper half of the disc to deflect fragments away from the operator (Correct answer)
- 90 degrees for grinding operations
- 360 degrees with only a gap for the workpiece contact point
- Guards on angle grinders are advisory only under PUWER
Correct answer: 180 degrees — the guard must cover at least the upper half of the disc to deflect fragments away from the operator
For angle grinders, BS EN 60745 and PUWER require the guard to cover at least 180 degrees of the disc (the upper half facing the operator). The lower 180 degrees is the working sector. The 180-degree guard deflects fragments from wheel burst away from the operator and prevents hand contact with the upper disc face.
Question 4: What action must be taken if the adjustable guard on a bench grinder cannot be positioned within 3mm of the wheel face?
- The wheel has worn too small and must be replaced — do not continue using the machine with an inadequate guard-to-wheel gap (Correct answer)
- The gap is acceptable up to 10mm if a secondary safety screen is fitted
- Adjust the work rest to compensate for the guard gap
- Remove the guard and use only a face shield as a substitute
Correct answer: The wheel has worn too small and must be replaced — do not continue using the machine with an inadequate guard-to-wheel gap
As a grinding wheel wears, the guard must be adjusted to maintain the correct clearance. If adjustment is no longer possible because the wheel has worn to minimum usable size, the wheel must be replaced. Using a wheel that has worn beyond the point where the guard can be properly adjusted compromises both burst protection and contact prevention.
Question 5: A worker removes the guard from an angle grinder claiming it is needed to access a confined area. What is the correct response?
- Work must stop — the guard must not be removed; if the area is inaccessible with the guard, an alternative tool or method must be found (Correct answer)
- Guard removal is acceptable if the work lasts less than 5 minutes
- Guard removal can be authorised by the supervisor if access is genuinely restricted
- A smaller angle grinder with its guard in place is acceptable only if the same disc size is used
Correct answer: Work must stop — the guard must not be removed; if the area is inaccessible with the guard, an alternative tool or method must be found
Removing a guard from an angle grinder is prohibited under PUWER 1998 and is a serious criminal offence. If access is the issue, the correct solution is to select a smaller angle grinder with guard, or use an alternative tool. Access difficulties do not justify accepting the catastrophic consequences of unguarded disc burst or contact injury.
Question 6: What is the role of the 'tongue guard' (spark deflector) on a bench grinder?
- To limit the top portion of wheel exposure to a maximum gap and deflect sparks and fragments downward, away from the operator's eyes (Correct answer)
- To prevent the workpiece from being dropped into the guard housing
- To prevent the grinding wheel from contacting the guard body during operation
- To indicate the correct grinding angle to the operator
Correct answer: To limit the top portion of wheel exposure to a maximum gap and deflect sparks and fragments downward, away from the operator's eyes
The tongue guard (adjustable top guard) on a bench grinder closes the gap at the top of the wheel to a maximum specified distance (typically 6mm from wheel surface). It deflects sparks, grinding particles, and potentially wheel burst fragments downward rather than towards the operator's face. It must be adjusted as the wheel diameter reduces.
Abrasive Wheels Training Certificate Guarding Requirements
What does PUWER 1998 Regulation 11 require regarding guards on abrasive wheel machines?