Read a Dial Indicator
Dial indicators are used to measure points on a 3-dimensional surface that would be impossible to measure with linear measuring tools. They can be used to measure outer surfaces or the inner expanses of apertures, such as holes. Dial indicators are available at hardware stores. Use these tips to learn how to read a dial indicator.
Contents
Steps
Prepare the Dial Indicator for Use
- Loosen the beam lock of the dial indicator.
- Slide the indicator back and forth to check for smooth operation.
- Close the large flat dial indicator jaws by bringing them fully together. Check that the dial now reads 0.
Take the Desired Measurement
- Measure outer surfaces by closing the large flat jaws of the dial gauge gently on the part to be measured.
- Measure a cylindrical surface, such as a pipe, by making sure that the body of the dial gauge is held perpendicular to the axis of the cylinder. Failure to hold the dial gauge perpendicular to the axis of the cylindrical body being measured will cause inaccurately large measurements.
- Measure inner apertures with the smaller pointed jaws on the back of the dial gauge head. Insert the small jaws into the aperture and extend them until they touch the inner surfaces.
- Measure the inside diameter of a round hole by making sure that the body of the dial gauge is held in the same plane as the hole. Failure to hold the dial gauge body in the plane of the hole will result in inaccurately large measurements.
- Measure the inside diameter of a round hole by making sure that the dial gauge jaws are measuring the full diameter of the hole. Keep one jaw of the dial gauge in place and sweep the other back and forth. Find the spot where the dial gauge jaw being swept no longer has the room to sweep. This technique will result in the measurement of the full diameter of the hole.
Obtain the Measurement Reading From the Dial Gauge
- Determine the position of the leading surface of the dial gauge head along the marked scale on the body of the dial gauge. The lines on the body are numbered, with each number representing a step of 1 cm (0.394 inches). There are 10 unnumbered lines between the numbered lines. Each unnumbered line represents 0.1 cm (0.039 inches). Use the highest line that is visible to the left of the leading surface of the dial gauge head. For example, if the highest line to the left of the leading edge of the dial gauge head is 2 unnumbered lines above the numbered line 3, note that as 3.2 cm (1.260 inches).
- Convert the reading to mm. Multiply by 10. In the example started above, 3.2 cm (1.260 inches) is changed to 32 mm (1.260 inches).
- Obtain the reading from the dial of the dial gauge. One full revolution of the dial represents 1 mm (0.0394 inches). 100 divided lines are shown on the face of the dial gauge to give a resolution of 0.01 mm (0.0039) per line. Add this to the reading. To continue the example started above, a dial reading of 64 would add 0.64 mm (0.025 inches) to the number measured as 32 mm (1.260 inches). This brings the final measurement to 32.64 mm (1.285 inches).
Things You'll Need
- Dial indicator
