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How to use a tubular
inside micrometer

Shop for Micrometers
When taking some internal measurements, you may need to use an extension rod if the measuring capacity of your micrometer is not great enough. When taking internal measurements, you may need to use an extension rod if the measuring capacity of your micrometer is not great enough.
To select the correct extension rod, insert each of the rods provided with your micrometer into the tool and hold them inside the space to be measured. To select the correct extension rod, insert each of the rods provided with your micrometer into the instrument and hold them inside the space to be measured.
The correct rod will be the largest one that can be fitted into hole or space. The correct rod will be the largest one that can be fitted into the hole or opening.
Step 1 When you have determined which rod to use and have attached it to the end of the micrometer, turn the thimble until the micrometer reads zero.

Step 1 – Zero micrometer

When you have determined which rod to use and have attached it to the end of the micrometer, turn the thimble until the micrometer reads zero.

Step 2 Insert the micrometer into the hole you are measuring.

Step 2 – Insert micrometer

Insert the micrometer into the opening you are measuring.

Step 3 Rotate the thimble until the measuring faces of the micrometer make contact with the edges of the space being measured. Pivoting the tool whilst you turn the thimble will ensure that the micrometer is as horizontal as possible. Do not use excessive force; light but firm pressure ensures accurate measurements.

Step 3 – Rotate thimble

Turn the thimble using the ratchet speeder until the spindle is close to the object. As you approach the edge of the hole, pivot the micrometer, keeping it square. Continue turning until the spindle stops rotating.

The ratchet will keep turning, applying the correct amount of force for an accurate measurement. Using the thimble alone requires a degree of skill and practice to achieve the correct “feel”.

Step 4 Turn the lock nut to secure the distance between the measuring faces so that you can remove the micrometer. Read the measured value (See How to Read a Micrometer).

Step 4 – Turn locking device

Turn the lock nut to secure the distance between the measuring faces so that you can remove the micrometer.

To acquire the actual measurement of the inside diameter or expanse, add the size of the extension rod to the measured value indicated on the micrometer scale.

See How to read a metric micrometerfor additional information on reading the scale.

Wonkee Donkee says: 'When taking measurements, try not to touch the measuring faces of the micrometer. Even the smallest amount of oil on your hands can affect the accuracy of your readings.'