A dial indicator is a device used to measure tiny increments. It is used in the mechanized process to quantify the precision of metal parts. There are usually three types of incremental measures used by the dial indicator. The largest increase is .005, pronounced five hundredth of an inch. The smallest is .001, pronounced one-thousandth of an inch. The most accurate measurements are .0001, called ten-thousandth of an inch. Reading a dial indicator is just a matter of understanding the two dials in the large indicator. A small dial, located at the bottom of the large pointer, indicates a revolution of the large dial in a movement of .100. The large indicator is made up of the measures of the small indicators. The precision of the specification of the measurement of the indicators is always shown on the face of the device. For the lower example, the indicator drive arm has a total movement of 1 inch and is divided into .0001 “increments.
- Notice the large dial on the side of the indicator. The large dial has numbers graded by 10. It is numbered from 0 to 90. Between each number 9 small lines are indicating a measure of .001 “.
- Notice the smallest dial placed under the big needle of the movement .001. “It has numbers on the front side and is also divided into ten separate numbers. The range is from .0 to.9, where .9 equals .900 “or nine-thousandths of an inch. One inch in this dial indicator is equal to the reading 1,000 “.
- Adjust the indicator to zero by loosening the outer indicator ring. You must be able to relax a hand screw and tighten it to adjust the measuring ring to .001. “By moving the ring to zero, you can calibrate the indicator in any position.
- Press the indicators arm. Adjust the dials to the next position. The small dial is at .4 “. The large dial at 10. The ring reading would be .410”.
- Releases some pressure in the movement arm. Lower the large dial 5 lines below 10. The reading in inches is now .405 “.
- Let the dial indicator return to zero by releasing the drive arm. Check the outer ring twice to register that the 0 is below the large dial on the front display.
- Move the indicator to the next position. Place the small dial on .1 and the large five lines after the number 20. The reading in inches is .125 “or 1/8 of an inch.
- Reduce the rod even further until the small dial is at .2 and the larger dial at 50. The reading is now .250 “or 1/4 inch.
- Push the rod a little further until the small dial is at .5 and the large dial at 0. This indicates that the drive arm has now moved .500 “or 1/2 inch.
- You can practice a little more by moving your arm to the following positions. The small dial in .3 and the large 5 lines after the 70, which is equal to .375 “or 3/8 of an inch, the small dial in .6 and the large 5 lines after the 20, which equals. 625 “or 5/8 inch. The small dial in .7 and the large dial in 50, which is equal to .750 “or 3/4 of an inch.