Grinding technology: The overall structure (spacing and openness) of a grinding wheel primarily depends on which factors?

Introduction / Context:
Choosing a grinding wheel is not only about abrasive and bond. The wheel structure—how open or dense the wheel is—directly affects chip accommodation, wheel loading, and thermal behavior. Successful grinding requires matching structure to job conditions.

Given Data / Assumptions:

• Structure refers to the relative spacing between abrasive grains.
• Other parameters (abrasive type, grit size, grade, bond) are held constant for comparison.
• We consider typical shop operations: rough grinding, finish grinding, and varying workpiece hardness.

Concept / Approach:
Open structures provide larger chip spaces and are preferred for soft, gummy materials or heavy stock removal to prevent loading. Denser structures support finer finishes on harder materials where chip volumes are lower. Thus, structure selection depends on work hardness, operation type, and finish requirement.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer selection charts map structure numbers to application classes: roughing vs finishing and work material characteristics corroborate this logic.

Why Other Options Are Wrong:

• Only hardness: ignores process intent and finish goals.
• Only operation nature: neglects work material response.
• Only finish: without considering chip load and material behavior, finish alone is insufficient.

Common Pitfalls:
Selecting a dense wheel for gummy materials leads to glazing and burn; conversely, overly open wheels can harm dimensional control on hard parts.

Final Answer:
All of these