Grinding wheel grit size vs. work material A coarse-grained grinding wheel is best suited for which type of materials to avoid wheel loading and improve chip accommodation?
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AHard and brittle materials
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BSoft and ductile materials
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CHard and ductile materials
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DSoft and brittle materials
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EGlass and fused silica only
Answer
Correct Answer: Soft and ductile materials
Explanation
Introduction / Context:Wheel selection must match work material characteristics. Grain size affects chip space and cutting aggressiveness. Soft, ductile materials tend to smear and clog wheels, so grit size and structure are crucial to performance and finish.
Given Data / Assumptions:
- Conventional abrasives and bonds (aluminium oxide or silicon carbide).
- Goal is efficient cutting with minimal loading and burning.
Concept / Approach:Coarse grains create larger chip pockets and stronger points, enhancing chip evacuation and reducing loading on ductile materials. For hard-brittle materials, finer grits can control micro-fracture and surface integrity; coarse grit may cause chipping.
Step-by-Step Solution:
Identify loading tendency on soft, ductile materials.Select coarse grit to increase chip clearance and promote self-sharpening.Conclude: coarse-grained wheels are preferred for soft, ductile materials.Verification / Alternative check:Handbooks advise coarse/open-structure wheels with softer grade for aluminium and mild steels to prevent glazing.
Why Other Options Are Wrong:Hard-brittle materials often benefit from finer grit control. “Glass only” is too narrow and misinterprets the role of grit size.
Common Pitfalls:Choosing fine, hard wheels on soft metals leads to glazing, heat, and poor finish.
Final Answer:
Soft and ductile materials