what is Micrometer Screw gauge: Working Principle, construction, Reading measurements

What is Micrometer Screw gauge: 

A micrometer, also known as a micrometer screw gauge or a micrometer caliper, is a precision measuring instrument used to measure the thickness or diameter of an object with a high degree of accuracy. It is commonly used in manufacturing, engineering, and scientific applications where precise measurements are required.

A micrometer typically consists of a calibrated screw with a spindle at one end and an anvil at the other. The object to be measured is placed between the spindle and the anvil, and the screw is turned until the spindle makes contact with the object. The measurement is then read from the calibrated scale on the micrometer.

Micrometers are available in different types, including outside micrometers for measuring the external diameter of an object, inside micrometers for measuring the internal diameter of an object, and depth micrometers for measuring the depth of a hole or slot. They are capable of measuring dimensions within the range of 0.001 mm to 300 mm, depending on the type and design of the micrometer.

Types of micrometer:

There are several types of micrometers available, including:

1. Outside Micrometer.

2. Inside Micrometer.

3. Depth Micrometer.

4. Digital Micrometer.

5. Vernier Micrometer.

6. Screw Thread Micrometer.

7. Gear Tooth Micrometer.

8. Bore Micrometer.

9. Blade Micrometer.

10. Optical Micrometer.

1. Outside Micrometer: The most common type of micrometer, used for measuring the outer diameter of objects.

2. Inside Micrometer: Used to measure the internal diameter of objects, such as pipes and cylinders.

3. Depth Micrometer: Used for measuring the depth of holes, slots, and other recesses.

4. Digital Micrometer: A micrometer with a digital readout for more accurate and precise measurements.

5. Vernier Micrometer: A micrometer with a vernier scale for measuring more accurately than a standard micrometer.

6. Screw Thread Micrometer: Used to measure the pitch diameter of screw threads.

7.Gear Tooth Micrometer: Used to measure the thickness of gear teeth.

8. Bore Micrometer: Used to measure the diameter of large holes and bores.

9. Blade Micrometer: Used for measuring the thickness of sheet metal and other thin materials.

10. Optical Micrometer: Uses optical techniques for measuring very small distances.

These are some of the common types of micrometers, and there may be other specialized micrometers for specific applications as well.

Working principle:

The basic working principle of a micrometer is based on the screw and nut mechanism.

• The micrometer consists of a C-shaped frame, a spindle, a thimble, a sleeve, a ratchet, and a measuring face. The spindle is a threaded shaft that moves through the sleeve. The sleeve is fixed to the C-shaped frame, and the thimble is attached to the spindle. The measuring face is at the end of the spindle, and it is usually made of carbide or other hard materials to ensure accuracy.
• To measure an object, the spindle is rotated by turning the thimble, and the object is placed between the measuring face and the anvil (a flat surface opposite the measuring face). As the spindle rotates, it moves through the sleeve and advances towards the anvil until it touches the object. The thimble has a scale marked on it, which provides a reading of the distance the spindle has traveled.
• The reading is taken by aligning the markings on the sleeve and thimble. The sleeve has a scale marked on it, which is divided into equal parts called graduations. Each graduation represents a certain distance, usually 0.5mm or 0.1mm. The thimble has a circular scale marked on it, which is divided into 50 or 100 equal parts called divisions. Each division represents a distance of 0.01mm or 0.001mm, depending on the micrometer.
• When the spindle touches the object, the thimble is rotated until the measuring face is in contact with the object. The reading is taken by adding the number of graduations on the sleeve to the number of divisions on the thimble that align with the sleeve scale. The result gives the thickness or diameter of the object being measured.

Construction of micrometer:

The following are the basic components of a micrometer:

1. Frame: The frame of the micrometer is the main body of the instrument. It is usually made of metal and has two arms, one of which houses the measuring spindle and the other houses the stationary anvil.

2. Spindle: The spindle is a threaded rod that moves in and out of the frame. The spindle is attached to the thimble and moves when the thimble is rotated.

3. Thimble: The thimble is a rotating collar that is attached to the spindle. The thimble has a circular scale engraved on it that is used to measure the distance between the spindle and the anvil.

4. Anvil: The anvil is a fixed surface that is used to measure the distance between it and the spindle. The anvil is usually a flat surface that is perpendicular to the spindle.

5. Sleeve: The sleeve is a hollow cylinder that fits over the spindle and the anvil. The sleeve is used to protect the spindle and the anvil from damage and also to provide a smooth sliding surface for the thimble.

6. Locking lever: The locking lever is used to lock the spindle and the anvil in place once the measurement has been taken.

To use a micrometer, the user rotates the thimble to move the spindle towards the anvil. The user then places the object to be measured between the spindle and the anvil and continues to rotate the thimble until the spindle and the anvil gently touch the object. The user then reads the measurement on the scale of the thimble and the sleeve.