How to Read Metric Depth Micrometers

Written by emile heskey | 13/05/2017
How to Read Metric Depth Micrometers
A depth micrometer can find the depth of a hole. (wood hole image by Allyson Ricketts from

Using a metric depth micrometer involves two sets of skills. You will need to know how to use a depth micrometer to find the depth of holes or other gaps. You will also need to know how to convert metric units to Imperial measurements. By combining these skills, you will be able to use a depth micrometer in your projects without having to buy one calibrated for imperial units. Using a simple calculation, you can convert units and make your micrometer useful.

Place the depth micrometer over the hole you are attempting to find the depth of. Place it squarely, so that the base of the device is flat.

Twist the ratchet clockwise to extend the spindle. Keep twisting until the spindle face touches the base of the hole. You will no longer be able to turn the ratchet. Look at the figure on the sleeve. The thimble will indicate the depth of the hole by moving down the sleeve.

Work out the amount that is shown on the micrometer face. The numbers that are obscured by the thimble on the sleeve are millimetres, usually with half millimetres marked with a smaller dash. The numbers printed on the sleeve are usually hundredths of a millimetre. The area where the sleeve meets the thimble will tell you the depth of the hole in millimetres, half millimetres and hundredths of a millimetre. Add these together to find the precise depth of the hole.

Convert the reading into inches if you want them to be in Imperial measurements. If the units used are millimetres, divide by 10 to find centimetres. Twenty-three millimetres is 2.3 centimetres. Multiply the centimetres by 0.393700 to find it in inches. One inch equals 2.54 centimetres.

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