Grinding machines :
A grinding machine is a power-operated machine tool where the workpiece is fed against a constantly rotating abrasive wheel to remove the thin layer of material from work.
Grinding Wheel :
• A grinding wheel is a multi-tooth cutter made up of many hard particles known as abrasives which have been crushed to leave sharped edges for machining
• Every grinding wheel has two constituents:
• Abrasive used for cutting
• Bond that holds the abrasive materials
Functions of Grinding Wheel :
- Removal of stock
- Generation of flat, curved and cylindrical surfaces
- Production of highly finished surfaces
- Cutting off operations
- Production of sharp edges and points
Principle of the grinding process:
• The workpiece is fed against the rotating abrasive wheel.
•Due to the action of rubbing or friction between the abrasive particles and workpiece material is removed.
Purpose of grinding:
•Grinding is a surface finishing operation where a very thin layer of material is removed in the form of dust particles.
• The thickness of the material removed is in the range of 0.25 to 0.50 mm.
• The tool used is an abrasive wheel.
Grinding process :
Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.
Abrasives :
- Abrasive is the material employed for sharpening, grinding and polishing operations.
- Natural abrasive – emery, corundum, quartz, sandstone, diamond, etc.
- Artificial abrasive – carborundum, aloxite, alundum, etc.
Applications of abrasives:
Corundum :
- It is a natural mineral consisting of aluminium oxide. Hardest natural substance after diamond.
- Used for shaping, finishing and polishing other tools.
Emery :
- natural abrasive consisting of aluminium oxide and a small amount of iron oxide.
Silicon carbide :
- Synthetic abrasive is harder than aluminium oxide.
- Used to grind metals like iron, brass and soft bronze.
- Used in non-metals like wood and leather industries.
Zirconia aluminia :
- It is a mixture of zirconium oxide and aluminium oxide.
- Used in casting and foundry industries.
Cubic boron nitride :
- It is made up of boron nitride with a cubic crystalline structure.
- Used for hard coating material.
Diamond :
- Industrial diamonds are used in grinding wheels as an abrasive material. These diamonds are specifically processed for industrial applications, rather than for jewellery.
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