Dial Test Indicator for Parallelism & Concentricity and Grinding Wheel – Abrasive, Grit, Grade, Bond

In the ITI Turner trade, precision measurement and finishing operations are essential for producing high-quality components. Instruments like the dial test indicator (DTI) are used to check alignment, while grinding wheels are used for finishing operations. This chapter explains the use of dial test indicators for checking parallelism and concentricity, along with the important elements of grinding wheels.

Dial Test Indicator (DTI)

Introduction

A dial test indicator is a precision measuring instrument used to detect small variations in alignment, flatness, and concentricity. It is widely used in lathe work for inspection and setup.

Construction

• Dial with pointer
• Lever-type stylus
• Gear mechanism
• Magnetic stand or holder

Working Principle

The stylus moves when it comes in contact with the surface, and this movement is magnified and shown on the dial.

Use for Parallelism

Procedure

• Fix DTI on magnetic stand
• Place stylus on work surface
• Move the carriage along the surface
• Observe dial reading

If the reading remains constant, the surface is parallel. Any variation indicates lack of parallelism.

Use for Concentricity

Procedure

• Mount workpiece on lathe
• Place stylus on outer surface
• Rotate the workpiece
• Observe dial variation

If the reading is constant, the workpiece is concentric. Variation indicates eccentricity.

Other Uses

• Checking run-out
• Aligning machine components
• Measuring small displacements

Advantages

• High accuracy
• Easy to use
• Sensitive measurement

Precautions

• Handle carefully
• Avoid shock
• Ensure proper contact

Grinding Wheel

Introduction

A grinding wheel is a cutting tool used for finishing and shaping materials. It consists of abrasive particles bonded together.

Main Elements of Grinding Wheel

1. Abrasive

Abrasives are the cutting particles in the grinding wheel.

• Aluminium oxide (for steel)
• Silicon carbide (for non-ferrous materials)

2. Grit

Grit refers to the size of abrasive particles.

• Coarse grit → Fast cutting
• Fine grit → Smooth finish

3. Grade

Grade indicates the hardness of the wheel.

• Soft grade → For hard materials
• Hard grade → For soft materials

4. Bond

Bond holds abrasive particles together.

• Vitrified bond
• Resinoid bond
• Rubber bond

Functions of Grinding Wheel

• Material removal
• Surface finishing
• Sharpening tools

Selection of Grinding Wheel

• Material of workpiece
• Type of operation
• Required finish

Application in Turner Workshop

In the Turner trade, dial test indicators are used for checking alignment and accuracy, while grinding wheels are used for finishing operations and tool sharpening.

Proper use of these tools ensures high-quality machining.

Importance

• Ensures precision
• Improves surface finish
• Enhances productivity

Conclusion

Dial test indicators and grinding wheels are essential tools in the ITI Turner trade. DTIs help in checking parallelism and concentricity, while grinding wheels are used for finishing operations.

Understanding their construction, use, and selection ensures accurate and efficient machining.

In conclusion, mastering these tools is important for achieving precision and quality in engineering work.