Calipers – Types and Uses (Firm Joint) in ITI Turner Trade

In the ITI Turner trade, accurate measurement is essential for producing high-quality components. Calipers are important measuring tools used to compare dimensions, check sizes, and transfer measurements from one place to another. This chapter focuses on firm joint calipers, their types, construction, and uses in workshop practice.

Introduction to Calipers

Calipers are measuring instruments used to measure the distance between two opposite sides of an object. Unlike precision instruments such as micrometers, calipers are mainly used for comparison measurements rather than direct reading.

In the Turner workshop, calipers are widely used for checking external and internal dimensions of workpieces.

Firm Joint Calipers

Firm joint calipers are the simplest type of calipers. In these calipers, the two legs are joined together at a fixed pivot point. The movement of the legs is controlled manually, and they maintain their position due to friction at the joint.

These calipers are easy to use and are commonly used for rough measurement and comparison work.

Construction of Firm Joint Calipers

A firm joint caliper consists of the following parts:

• Legs: Two curved or straight arms used for measurement
• Joint (Pivot): Connects the legs and allows movement
• Tips: The ends of the legs that touch the workpiece

The joint is designed to provide sufficient friction so that the caliper retains its set position during use.

Material Used for Calipers

Calipers are made from high-quality carbon steel or tool steel. The material is hardened and tempered to provide strength, durability, and resistance to wear.

• Strong and durable material
• Resistant to bending and deformation
• Long service life

Types of Firm Joint Calipers

1. Outside Caliper

Outside calipers are used to measure the external dimensions of a workpiece such as diameter, thickness, or width.

• Legs are curved inward
• Used for shafts, rods, and external surfaces

2. Inside Caliper

Inside calipers are used to measure internal dimensions such as the diameter of holes or slots.

• Legs are curved outward
• Used for holes, bores, and cavities

3. Odd Leg Caliper (Jenny Caliper)

This type has one straight leg and one bent leg. It is used for marking lines parallel to an edge and for layout work.

• One leg acts as a guide
• Other leg is used for marking

Uses of Firm Joint Calipers

Firm joint calipers are widely used in workshop operations:

• Measuring external and internal dimensions
• Comparing sizes of workpieces
• Transferring measurements from one object to another
• Checking uniformity of parts

Working Principle

The working principle of calipers is based on comparison measurement. The caliper is adjusted to match the dimension of the workpiece, and then the measurement is compared with a scale or standard.

This method provides quick and reliable results for general workshop use.

Advantages of Firm Joint Calipers

• Simple construction
• Easy to use
• Low cost
• Suitable for rough measurement

Limitations of Firm Joint Calipers

• Less accurate compared to precision instruments
• No direct reading scale
• Depends on user skill

Precautions While Using Calipers

To ensure accurate measurement and safety, the following precautions should be followed:

• Do not apply excessive force
• Ensure proper contact with workpiece
• Avoid using worn or damaged calipers
• Handle with care to maintain accuracy

Maintenance of Calipers

Proper maintenance increases the life and accuracy of calipers:

• Keep calipers clean and dry
• Apply light oil to prevent rust
• Store in a safe place
• Avoid dropping or bending

Application in Turner Workshop

In the Turner trade, firm joint calipers are used for checking the diameter of shafts, internal diameters of holes, and thickness of workpieces. They are also used in layout work and during machining operations for quick measurement.

These tools help maintain accuracy and consistency in production.

Conclusion

Calipers are essential measuring tools in the ITI Turner trade. Firm joint calipers, being simple and reliable, are widely used for comparison measurement and general workshop tasks.

Understanding their types, construction, and uses helps trainees perform accurate measurements and improve their machining skills.

In conclusion, proper use and maintenance of calipers ensure better performance, accuracy, and efficiency in workshop operations.