Grinding wheel structure numbering and density In manufacturing processes, the 'structure' number of a vitrified grinding wheel indicates the relative spacing between abrasive grains. Based on standard wheel nomenclature, is a dense (closely packed) structure correctly denoted by higher structure numbers such as 9 to 15 (or above)?

Introduction / Context:
Grinding wheel codes include grit size, grade, structure, and bond. Among these, the structure number describes how tightly or loosely the abrasive grains are packed. Correct interpretation of this number influences stock removal rate, wheel wear, and surface finish.

Given Data / Assumptions:

• Conventional vitrified wheels used for general grinding.
• Structure numbers typically range from about 1 (very dense) to 15 (very open).
• Other variables (grit size, grade, bond) are kept constant for comparison.

Concept / Approach:
Structure number ↑ means more spacing and porosity between grains. Dense wheels (low structure number) have more cutting points per unit area and usually produce finer finishes but load more easily. Open wheels (high structure number) admit coolant and chips more readily, useful for softer or gummy materials and heavy cuts.

Step-by-Step Solution:
Define density: closely packed grains = dense structure.Relate to numbering: lower structure numbers (about 1–5) = dense; higher numbers (about 9–15) = open.Therefore, stating that dense wheels are ”9–15 or higher” is incorrect.

Verification / Alternative check:
Manufacturing catalogs list structure progression from dense to open as the number increases, confirming the interpretation.

Why Other Options Are Wrong:

• “Only for coarse grits”: structure is independent of grit size.
• “Depends on grade”: grade is bond hardness, not grain spacing.
• “Bond type indicates density”: bond affects strength and porosity type, but structure number explicitly denotes spacing.

Common Pitfalls:
Confusing grade (hard/soft) with structure (dense/open); assuming higher number always means ”more/better.”

Final Answer:
No, higher structure numbers mean a more open (less dense) wheel