Useful Tips of Using the Micrometer Caliper
We can use a micrometer caliper to measure the size of objects with a precision of one hundredth of a millimetre.The object to be measured should be placed between the jaws of the micrometer and the jaws are carefully closed on the object by rotating the thimble.The distance between the jaws and the size of the object is read on the barrel of the micrometer. A micrometer caliper works on the principal of a screw. If a screw is turned by one revolution, it advances by a distance equal to the pitch of the screw. Then a fraction of a rotation advances it by a corresponding fraction of the pitch. It is common that a micrometer caliper to have a screw with a pitch of 0.5 mm per revolution, and a thimble calibrated in fiftieths of a revolution.One fiftieth of a revolution is equal to 0.01 mm travel of the screw, so the readings on the thimble give the distance that the screw has moved to the nearest 0.01 mm.
Calibration marks on the sleeve of the micrometer give readings of how far the jaws are open to the nearest 0.5 mm.The reading on the sleeve is added to the reading on the thimble to give the total distance between the jaws of the micrometer. Micrometer calipers often do not read zero when the jaws are closed.To correct for this, a“zero reading”must always be taken. This zero reading is then either added to or subtracted from the reading obtained for the object. If the zero reading is below the reference mark, it is added to the reading; if it is above the reference mark, it is subtracted from the reading.
It is extremely important for us to close the micrometer caliper gently any where at any time because the screw has a very high mechanical advantage and a large tension can easily be put on the jaws if one is not careful. Use the ratchet on the end of the thimble if there is one.This will automatically put the correct tension on the jaws.When you are finished using a micrometer caliper, always put it away with the jaws slightly open to allow for any thermal expansion.