Grinding Wheel
A grinding wheel is a cutting tool used for grinding, sharpening, and finishing metal surfaces. It consists of abrasive particles bonded together to form a circular wheel. Grinding wheels are commonly used in bench grinders, surface grinders, and cylindrical grinders for removing small amounts of material and improving surface finish.
Abrasive Materials
Abrasives are hard particles used in grinding wheels to remove material from the workpiece. Common abrasive materials include:
- Aluminium Oxide: Used for grinding steel and ferrous metals.
- Silicon Carbide: Used for grinding non-ferrous metals, cast iron, and carbide tools.
- Cubic Boron Nitride (CBN): Used for grinding hardened steel.
- Diamond: Used for grinding very hard materials such as ceramics and carbide.
Grade of Grinding Wheel
The grade of a grinding wheel refers to the strength with which the abrasive particles are held by the bonding material.
- Soft Grade: Abrasive particles break away easily.
- Medium Grade: Used for general grinding work.
- Hard Grade: Abrasive particles are held strongly by the bond.
Structure of Grinding Wheel
The structure refers to the spacing between abrasive grains in the grinding wheel.
- Dense Structure: Abrasive grains are closely packed.
- Open Structure: Abrasive grains are spaced farther apart.
Bond of Grinding Wheel
The bond is the material that holds abrasive grains together in the grinding wheel.
- Vitrified Bond: Made from clay and ceramic materials.
- Resinoid Bond: Made from synthetic resins.
- Rubber Bond: Used for flexible grinding wheels.
- Shellac Bond: Used for fine finishing.
- Metal Bond: Used for diamond wheels.
Specification of Grinding Wheel
Grinding wheels are specified by several factors such as abrasive type, grain size, grade, structure, and bond type.
Example specification:
A 46 K 5 V
- A – Type of abrasive (Aluminium oxide)
- 46 – Grain size
- K – Grade
- 5 – Structure
- V – Bond type (Vitrified)
Uses of Grinding Wheels
- Sharpening cutting tools
- Finishing metal surfaces
- Removing burrs
- Grinding weld joints
- Shaping metal parts
Mounting of Grinding Wheel
Proper mounting of the grinding wheel is important for safe operation.
- Check the wheel for cracks before mounting.
- Ensure the wheel size matches the grinder.
- Use proper flanges and washers.
- Tighten the wheel securely but not excessively.
- Run the machine at idle speed for a short time to check balance.
Dressing of Grinding Wheel
Dressing is the process of removing dull abrasive grains and exposing new sharp cutting edges. It also restores the correct shape of the grinding wheel.
Dressing tools include:
- Diamond dresser
- Star wheel dresser
- Abrasive stick
Selection of Grinding Wheels
The selection of a grinding wheel depends on several factors such as the type of material, grinding operation, and required surface finish.
- Use aluminium oxide wheels for steel and ferrous metals.
- Use silicon carbide wheels for non-ferrous metals.
- Select proper grain size depending on the finishing requirement.
- Choose suitable grade according to hardness of material.
Bench Grinder
A bench grinder is a machine used for grinding, sharpening, and polishing metal tools. It consists of a motor that rotates grinding wheels mounted on both sides of the shaft.
Parts of Bench Grinder
- Base: Supports the entire machine.
- Electric Motor: Provides power to rotate the grinding wheels.
- Grinding Wheels: Used for grinding operations.
- Wheel Guards: Protect the operator from sparks and fragments.
- Tool Rest: Supports the workpiece during grinding.
- Eye Shield: Protects the operator's eyes from sparks.
- Switch: Used to start or stop the machine.
Uses of Bench Grinder
- Sharpening cutting tools
- Grinding metal parts
- Removing rust and burrs
- Smoothing rough surfaces
Conclusion
Grinding wheels and bench grinders are essential tools used in mechanical workshops for sharpening and finishing operations. Understanding the abrasive materials, grades, structures, bonds, and proper selection of grinding wheels ensures safe and efficient grinding operations.