Grinding wheel grit size selection: The required abrasive grain size for a grinding wheel primarily depends on which factors?

Introduction / Context:
Grit size influences chip thickness, cutting force, and final surface finish in grinding. Selecting the proper grain size ensures the right balance between productivity and quality. The decision involves more than a single parameter; it is a multi-factor choice reflecting stock removal needs, work material properties, and finish specifications.

Given Data / Assumptions:

• Conventional bonded abrasive wheels (aluminium oxide or silicon carbide).
• Shop objectives may vary from roughing to fine finishing.
• Wheel structure and grade are held constant for discussion; focus is on grit size.

Concept / Approach:
Coarse grits remove stock quickly and tolerate large chip thickness, preferred for heavy allowances and tough materials when finish is secondary. Fine grits create many small cutting points for superior finish and dimensional control, especially on hard or brittle materials. Work material hardness affects grit choice: harder materials often require finer grits to avoid micro-fracturing of the surface and to maintain stable cutting action.

Step-by-Step Solution:

Verification / Alternative check:
Reference selection charts from wheel manufacturers correlate grit size with material hardness and finish grade; they consistently consider all three factors together.

Why Other Options Are Wrong:
Each single factor is relevant; therefore picking only one would be incomplete. The comprehensive and correct choice includes all listed factors.

Common Pitfalls:
Ignoring the interaction with wheel grade and structure; grit size should be chosen together with bond hardness and porosity to avoid wheel loading or excessive wear.

Final Answer:
all of these