The main types of calipers are outside calipers, inside calipers, odd-leg (Jenny) calipers, and Vernier calipers.
They are used to measure external dimensions, internal dimensions, and distances accurately.
Calipers are widely used in engineering, machining, and inspection work.

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Types of Calipers

What is a Caliper?

A caliper is a precision measuring instrument used to measure:

• External dimensions
• Internal dimensions
• Depths
• Steps

Calipers are widely used in:

• Mechanical engineering
• Manufacturing
• Quality control
• Tool rooms
• Automotive industries

They provide more accurate measurements than ordinary rulers.

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Main Types of Calipers

There are several types of calipers, each designed for specific measuring applications.

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1. Vernier Caliper

Definition

A vernier caliper is a precision instrument that uses a main scale and a vernier scale to obtain accurate measurements.

Parts

• Main Scale
• Vernier Scale
• Outside Jaws
• Inside Jaws
• Depth Rod
• Locking Screw

Measurements

External Measurement

Measures:

• Shaft diameter
• Plate thickness
• Rod diameter

Internal Measurement

Measures:

• Hole diameter
• Slot width

Depth Measurement

Measures:

• Hole depth
• Groove depth

Typical Accuracy

±0.02 mm

Advantages

✔ High accuracy
✔ No batteries required
✔ Durable

Disadvantages

✘ Requires reading skill

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2. Dial Caliper

Definition

A caliper that uses a dial indicator instead of a vernier scale.

Working Principle

A rack-and-pinion mechanism moves a pointer across a dial.

Features

• Easier to read than vernier calipers
• Quick measurement

Accuracy

Typically:

±0.02 mm

or

±0.001 inch

Advantages

✔ Easy reading
✔ Faster operation

Disadvantages

✘ Sensitive to shock

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3. Digital Caliper

Definition

An electronic caliper with a digital display.

Features

• LCD display
• Metric/Imperial conversion
• Zero setting at any position

Typical Accuracy

±0.01 mm

Advantages

✔ Very easy to read
✔ High accuracy
✔ Fast measurement

Disadvantages

✘ Requires batteries

Applications

• Inspection
• CNC machining
• Quality control

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4. Outside Caliper

Definition

A traditional caliper used to measure external dimensions.

Construction

Two curved legs with measuring points.

Uses

• Outside diameter of shafts
• Thickness of plates
• External dimensions

Limitation

Requires a scale or micrometer to obtain actual readings.

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5. Inside Caliper

Definition

A caliper used for measuring internal dimensions.

Uses

• Hole diameter
• Slot width
• Internal cavity measurements

Limitation

Actual measurement must be checked using a ruler or micrometer.

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6. Odd-Leg Caliper (Jenny Caliper)

Definition

A caliper with one pointed leg and one bent measuring leg.

Uses

• Scribing lines parallel to edges
• Marking workpieces

Applications

• Layout work
• Sheet metal fabrication

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7. Spring Caliper

Definition

A caliper equipped with a spring and adjusting screw.

Types

Spring Outside Caliper

Measures external dimensions.

Spring Inside Caliper

Measures internal dimensions.

Advantages

✔ Better adjustment control
✔ Improved accuracy

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8. Transfer Caliper

Definition

A caliper designed to transfer dimensions from difficult-to-access areas.

Uses

• Complex castings
• Grooves
• Recessed features

Advantage

Allows measurement transfer where direct measurement is difficult.

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9. Hermaphrodite Caliper

Definition

A special caliper having:

• One pointed leg
• One measuring leg

Uses

• Locating center lines
• Marking parallel lines

Applications

• Tool room work
• Layout operations

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10. Divider Caliper

Definition

A two-pointed instrument often classified with calipers.

Uses

• Transfer distances
• Divide lines equally
• Geometrical constructions

Applications

• Engineering drawing
• Layout work

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Classification by Measuring Function

Type	Purpose
Outside Caliper	External measurements
Inside Caliper	Internal measurements
Vernier Caliper	Precision measurements
Dial Caliper	Precision measurements
Digital Caliper	Electronic measurements
Odd-Leg Caliper	Marking and layout
Spring Caliper	Adjustable measurement
Transfer Caliper	Dimension transfer
Hermaphrodite Caliper	Center marking
Divider	Distance transfer

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Types of Measurements Performed by Calipers

External Measurement

Examples:

• Shaft diameter
• Pipe diameter
• Plate thickness

Internal Measurement

Examples:

• Hole diameter
• Bore diameter
• Slot width

Depth Measurement

Examples:

• Blind hole depth
• Groove depth

Step Measurement

Examples:

• Step heights
• Shoulder dimensions

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Comparison of Common Calipers

Feature	Vernier	Dial	Digital
Reading Method	Vernier Scale	Dial	LCD Display
Accuracy	High	High	Very High
Ease of Use	Moderate	Easy	Very Easy
Battery Required	No	No	Yes
Cost	Low	Medium	Higher

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Applications of Calipers

Manufacturing

• Part inspection
• Process control

Mechanical Engineering

• Machine component measurement

Automotive Industry

• Brake component inspection
• Engine part measurement

Quality Control

• Product verification

Tool Rooms

• Precision measurement work

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Advantages of Calipers

• Versatile measuring tool
• Measures inside, outside, and depth dimensions
• High accuracy
• Portable and easy to use
• Available in manual and digital forms

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Limitations of Calipers

• Less accurate than micrometers
• Requires proper handling
• Digital versions need batteries
• Dirt can affect readings

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Conclusion

Calipers are essential precision measuring instruments used in engineering, manufacturing, and quality control. The major types include Vernier Calipers, Dial Calipers, Digital Calipers, Outside Calipers, Inside Calipers, Spring Calipers, Odd-Leg Calipers, Transfer Calipers, Hermaphrodite Calipers, and Dividers. Among these, digital, dial, and vernier calipers are the most widely used today because they can accurately measure external, internal, depth, and step dimensions with high precision.

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