Micrometer, its construction, reading ITI fitter, and science 11 & 12 students

Micrometer Screw gauge

Micrometer Screw gauge. 

Introduction 

Micrometer screw gauge is a form of calipers used for measuring small dimensions. Screw gauge in extensively used in the engineering field for obtaining precision measurements. The article describes the principle and main parts of a basic micrometer screw gauge.

Micrometer screw gauge (or micrometer caliper) is an instrument or device for measuring the length of an object which is more precise than a ruler and vernier caliper. It because a micrometer screw gauge has the smallest scale of 0.01 mm. The device is widely used in mechanical engineering for measuring small diameter, thickness, or angles to a high degree of accuracy.

Screw gauge or micrometer screw gauge is a measuring instrument used for precision measurement. 

Micrometer Screw Gauge

Frame of Micrometer screw gauge

Anvil 

Spindle

Measuring faces

Main scale, Barrel or Sleeve

Thimble, Micrometer Scale

Ratchet stop

Spindle lock nut

Least count of Micrometer

Thimble one round.

1 mm displacement micrometer

Discount calculation

Micromete screw gauge

Micromete screw gauge

Micromete screw gauge

Micromete screw gauge

Micromete screw gauge

Objects measurement with Micrometer

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

Measuring of object with micrometer screw gauge

A screw gauge consists of a “U” shaped metallic structure, which is attached to a hollow cylindrical tube on one end. The hollow tube has a uniformly threaded nut inside it. A long stud with a plane face is fitted into this nut. Exactly on the opposite side of this nut and on the other end of the U shaped frame, a smaller stud with a plane face is also attached. Faces of both the studs are exactly parallel to each other.

This U shaped metallic structure is known as the frame of the micrometer screw gauge. the smaller stud is known as the anvil and the longer one is known as the spindle. the anvil is the fixed part of the device, whereas the spindle moves as and when the head is moved. the frame carries both the anvil and barrel, and is also heavier than the rest of the parts. The object to be measured is held between the anvil and the spindle.

The Barrel or sleeve is connects the frame to the cylindrical tube. It is a non-movable part of the screw gauge and has a scale inscribed over it which is the main scale of the device. Moreover, it also carries the most important part of the micrometer the screw.

The screw is the heart of the micrometer and is located inside the barrel. The screw converts small dimensions into measurable distance using a scale. The thimble or head is the end of the cylindrical tube and is turned to move and adjust the spindle. The thimble carries the vernier or secondary scale. There is one more part called the ratchet which is provided at the end of the tube. The ratchet is kind of limiting device which applies a pressure by slipping at a predetermined torque and thus prevents the spindle from moving further. Some screw gauges also consist of locking devices which holds the scales at a particular position for prevent any kind of error while taking readings.

A micrometer screw gauge also uses two scales –main and secondary scales. The secondary scale is provided on the thimble and is the measurement of the pitch of the screw. This means that the reading on the secondary scale measures the distance moved by the thimble per rotation. The scale on thimble is divided into 100 equal parts and measures hundredths of a millimeter. The thimble scale rotates over the spindle or the main scale. The main scale is a millimeter scale subdivided into equal parts with half a millimeter distance. When the object is to be measured, it is placed in between the anvil and the spindle. Readings from both the scales are taken into account for arriving at the final measurement.

Micrometer screw gauge is a delicate device and thus special care should be taken while handling it. Moreover, it is also important that the micrometer is well calibrated to prevent any kind of error in the final reading.

Precaution Steps

The spindle and anvil are cleaned with a tissue or cloth, so that any dirt present will not be measured.

Watch video to Learn reading of
Micrometer screw gauge reading without the help of tutor. It is very easy to understand.

Micrometer screw gauge: