Screw Gauge Experiment Introduction Edunovus Online Smart Practicals

Summary

The micrometer screw gauge is a precise instrument used to measure small objects, such as wire diameters. It works on the principle of a screw and nut mechanism, amplifying tiny linear movements into measurable rotations. The device features a linear scale (pitch scale) and a circular scale for accurate readings. The least count of the screw gauge is 0.01mm, making it highly precise. However, errors like zero error and backlash can affect measurements, and these must be corrected. The gauge is ideal for measuring small objects, such as the diameter of wires, with high accuracy.

Takeaways

• 😀 The screw gauge, also known as the micrometer screw gauge, is used for precise measurement of small objects such as wires.
• 😀 The principle behind the screw gauge is based on the micrometer screw principle, where a threaded screw moves linearly within a closely fitted nut.
• 😀 The distance moved by the screw in one full rotation is called the pitch and is constant.
• 😀 The screw gauge is equipped with two scales: the linear scale (or pitch scale) and the circular scale (or head scale).
• 😀 The pitch of the screw is the distance moved by the screw in one complete rotation and can be calculated using the linear scale readings.
• 😀 The least count of the screw gauge is derived by dividing the pitch by the number of divisions on the circular scale, and it is typically in micrometers.
• 😀 A common error in screw gauges is the zero error, where the zero of the circular scale does not coincide with the reference line of the linear scale.
• 😀 Zero error can be either positive or negative, and it affects the accuracy of the measurements taken.
• 😀 Backlash error occurs when there is a delay or jerky motion as the screw moves due to improper thread alignment.
• 😀 To find the diameter of a wire, the object is placed between the fixed stud and the screw, and the distance moved by the screw is measured to calculate the length.

Q & A

What is the micrometer screw gauge commonly used to measure?

The micrometer screw gauge is most commonly used to measure small objects such as wire, particularly the diameters of wires governed by standard numbers called standard wire gauges.

Why is the device called a 'screw gauge'?

It is called a screw gauge because it is most commonly used to measure the diameters of wires, which are defined by a standard system known as the standard wire gauge.

What is the principle behind the functioning of a micrometer screw gauge?

The micrometer screw gauge works on the principle of a micrometer screw, where an accurately cut single-threaded screw is placed inside a closely fitted nut and rotated, creating both circular and linear motion of the screw along its axis.

What is the pitch of a screw gauge and how is it calculated?

The pitch of the screw gauge is the linear distance moved by the screw in one complete rotation. It is calculated by measuring the linear scale readings before and after a complete rotation and dividing the difference by the number of rotations.

How do you determine the least count of a screw gauge?

The least count of a screw gauge is determined by dividing the pitch of the screw (the distance moved in one complete rotation) by the number of divisions on the circular scale. This gives the smallest measurable length, typically in micrometers.

What is zero error in a micrometer screw gauge, and how is it corrected?

Zero error occurs when the zero of the circular scale does not coincide with the reference line of the linear scale when the screw completely touches the fixed stud. If the zero of the circular scale is to the right of the reference line, it’s a positive error, and the correction is negative. If it’s to the left, it’s a negative error, and the correction is positive.

What is backlash error in a screw gauge?

Backlash error occurs when there is a lag in the linear movement of the screw, causing jerky motion or delayed movement in the opposite direction. This is due to improper alignment of the screw threads, which leads to irregular gaps or increased gaps between them.

How is zero error calculated in a screw gauge?

Zero error is calculated by observing the position of the zero on the circular scale relative to the reference line of the linear scale. Depending on whether the zero is to the right or left of the reference line, either a positive or negative correction is applied to the observed measurement.

How is the diameter of a wire measured using a screw gauge?

To measure the diameter of a wire, the wire is placed between the fixed stud and the screw. The screw is rotated using the ratchet until the wire is gently held. The diameter is the distance the screw has moved, which is the sum of the linear scale reading and the divisions crossed on the circular scale.

What does the term 'portion Y' refer to in the measurement of a wire's diameter?

Portion Y refers to the part of the screw's movement that is less than 1 mm, which is measured based on the divisions crossed on the circular scale. In the example, 31 divisions on the circular scale represent 0.31 mm, contributing to the total measurement of the wire's diameter.