Grinding practice – effect of glazing on performance In production grinding, “glazing” occurs when the abrasive grains become dull and the wheel surface turns shiny, causing rubbing instead of cutting. How does glazing influence the cutting capacity (material removal ability) of a grinding wheel?

Introduction / Context:
Glazing is a common phenomenon in grinding where the wheel surface becomes smooth and shiny because worn abrasive grains are not shed. Instead of sharp cutting points penetrating the work, glazed wheels rub and plough. Understanding its effect on cutting capacity is essential for choosing dressing frequency, wheel grade, and operating parameters.

Given Data / Assumptions:

• A vitrified or resinoid-bonded grinding wheel is in steady operation.
• Abrasive grains have dulled and are no longer fracturing or releasing.
• No significant change in machine power or coolant aside from the glazing condition.

Concept / Approach:
Cutting capacity depends on the number of active, sharp cutting points and their ability to penetrate the work. A glazed wheel presents rounded, blunt grains that slide on the surface, producing frictional heat. The lack of self-sharpening reduces chip formation and increases rubbing. Therefore, glazing must reduce the net material removal rate at the same feed and depth of cut.

Step-by-Step Solution:
Identify state: grains are dull and bond is holding them too firmly.Consequence: fewer effective cutting points, more rubbing and ploughing.Effect on process: higher grinding power and temperature for the same feed.Result: cutting capacity (MRR for given inputs) decreases; surface burn risk rises.

Verification / Alternative check:
Practical shop remedy for glazing is dressing the wheel to expose new sharp edges. A freshly dressed wheel immediately restores cutting action and lowers power draw at the same infeed, confirming that glazing had reduced cutting capacity.

Why Other Options Are Wrong:
“Increases” contradicts the loss of sharp points. “No effect” ignores the measurable rise in power and temperature. “Initially increases, then decreases” does not match glazing behavior; that describes certain wear-in phases, not glazing. “Reverses force direction” is unrelated to wheel sharpness.

Common Pitfalls:
Confusing glazing with loading (chip packing). Both reduce performance, but glazing stems from dull grains; loading stems from swarf clogging. Remedies differ in dressing aggressiveness and coolant strategy.

Final Answer:
Decreases cutting capacity