Grinding wheels: The statement “an open structure is denoted by structure numbers 1 to 8” is…

Introduction / Context:
The “structure” of a grinding wheel describes the relative spacing between abrasive grains. A more open structure contains more voids, enhancing chip accommodation and coolant access. Correctly interpreting structure numbers is important for selecting wheels for soft, gummy materials or heavy stock removal.

Given Data / Assumptions:

• Standard vitrified/resin wheel nomenclature: grain size – grade – structure – bond.
• Structure numbers increase with openness (more space between grains).
• Typical catalog ranges: roughly 1 (very dense) to around 12–15 (very open), depending on manufacturer.

Concept / Approach:
Lower structure numbers indicate denser wheels; higher numbers indicate open structures. Therefore, stating that “open structure is denoted by 1 to 8” is misleading, because 1 is actually very dense, and truly open wheels generally carry higher structure values than mid-range, often beyond 8.

Step-by-Step Solution:

Verification / Alternative check:
Consult any major wheel catalog: structure numbers are listed with qualitative descriptions (dense, medium, open). You will find openness correlated with higher numbers.

Why Other Options Are Wrong:
The claim cannot be made true by specifying special bonds or materials; the numeric convention is consistent across wheel types. Hence qualifiers about resin, diamond, or non-ferrous applications do not fix the incorrect statement.

Common Pitfalls:
Confusing “grade” (bond hardness) with “structure” (spacing); assuming a single vendor’s mid-range equals “open.” Always check the legend in the catalog used.

Final Answer:
Incorrect