Grinding practice – reducing glazing on a wheel: In production grinding, a wheel may “glaze” (dulled abrasive tips, shiny surface). Which change most effectively reduces glazing and restores cutting action?

Difficulty: Easy

Correct Answer: Using a softer wheel or by decreasing the wheel speed

Explanation:


Introduction / Context:
Glazing of a grinding wheel occurs when abrasive grains become dull but are not shed by the bond. The wheel surface turns shiny, chip space clogs, forces rise, temperature increases, and the part may burn. This question tests corrective actions rooted in grinding wheel selection and cutting speed control.



Given Data / Assumptions:

  • Wheel has glazed (dull cutting points, high rubbing).
  • Work material and coolant remain unchanged.
  • Machine is capable of adjusting wheel grade and speed (or allowing a wheel change).


Concept / Approach:
Abrasive self-sharpening relies on timely grain fracture or pull-out. If the wheel is too hard or the peripheral speed is too high, dull grains are held too strongly and continue rubbing. Selecting a softer grade promotes grain release; lowering wheel speed reduces rubbing and encourages renewed cutting.



Step-by-Step Solution:

Identify symptom: shiny wheel face, higher power, poor surface → glazing.Root cause: wheel too hard for the job or speed too high, so dull grains cannot dislodge.Corrective actions: choose softer grade to enhance self-sharpening; reduce wheel speed to reduce rubbing and heat.Supplement: increase infeed or dress more aggressively to open the wheel structure.


Verification / Alternative check:
After switching to a softer wheel or reducing speed, the specific grinding energy drops, sparks become more active, and the surface finish improves without burn—evidence of restored cutting.



Why Other Options Are Wrong:

  • Harder wheel/increase speed: aggravates glazing.
  • Harder wheel/decrease speed: still retains dull grains too long.
  • Softer wheel/increase speed: higher speed promotes rubbing; mixed outcome.
  • Dress less frequently: opposite of what is needed; dressing opens the wheel.


Common Pitfalls:
Confusing glazing with loading; loading is chip packing, fixed by dressing and coolant filtration, not merely wheel grade.



Final Answer:
Using a softer wheel or by decreasing the wheel speed

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