Grinding wheel behaviour: A wheel becomes “glazed” (glass-like cutting edge appearance) primarily due to

Introduction / Context:
Grinding performance depends on the interplay between abrasive grains and bond. When the abrasive tips dull but do not dislodge, the wheel “glazes,” rubbing instead of cutting, raising heat and harming finish.

Given Data / Assumptions:

• Conventional vitrified or resinoid bonded wheel.
• Work material causing dulling without sufficient self-sharpening.
• No recent dressing operation.

Concept / Approach:
Glazing occurs when cutting points flatten (wear) and the bond is too strong to release them. The wheel surface becomes shiny and slides on the work, increasing power draw and burning risk. Dressing restores sharpness by fracturing grains and exposing new edges.

Step-by-Step Solution:

Verification / Alternative check:
Power and temperature rise during glazing; dressing restores normal amperage and chip formation.

Why Other Options Are Wrong:

• Wear of bond: would cause wheel to act too soft, not glazed.
• Breaking of grains: produces fresh sharp edges—opposite of glazing.
• Cracks: a safety issue but not the mechanism for glazing.

Common Pitfalls:
Blaming only speed; while speed matters, incorrect grade and infrequent dressing are common root causes.

Final Answer:
Wear (dulling) of abrasive grains