A bore gauge measures the inside dimension of a bore, cylinder, or tube. It can be used with a micrometer or master calibration rings for an exact reading. Dial and electronic indicators are available, with variable size bases or interchangeable extension pins. The gauge is inserted into the opening and moved until centered, with a reading taken from the dial or electronic display. Fully electronic gauges are also available, with transducers and wired or wireless readouts. Extensions can be added for greater depth and size range.
A bore gauge is a measuring device for determining the inside dimension of a bore, cylinder or tube. In combination with a micrometer or master calibration rings, a bore gauge can give an exact reading of hole size. The measurement is achieved by inserting the base of the bore gauge into the opening to be measured and gently moving the base until it exactly fits the diameter of the opening. Available instruments include dial and electronic indicators with several basic configurations.
A dial bore gauge has a base with a fixed point on one side and a protruding pin on the opposite side which will retract when it contacts the inside wall of the pipe or cylinder. A spring-loaded centering mechanism in combination with a fixed and a movable point provides very exact measurements. These gauges can have variable size bases for use with a variety of aperture sizes or can have interchangeable extension pins to adjust the size of the base.
A user records a measurement of the inside diameter of the tube end and selects an appropriately sized base or extension pin. Using a master calibration ring or micrometer, the user determines the distance between the fixed point and the stud on the base and notes the reading. The dial reading on the indicator has a bezel that is zeroed to match the size of the base used.
The base is inserted into the tube opening at a slight angle. Once the base is inside, the user gently moves it back and forth until the gauge is centered in the tube. The bore is then removed from the tube and the measurement read off the dial. The result, a positive or negative number, is added or subtracted from the micrometer or master calibration ring measurement to calculate a final result.
Some gauges can replace the traditional dial with a digital or electronic display. An electronic readout is calibrated by measuring the base of the gauge in a master calibration ring. Any subsequent measurements are compared to that calibration point. The base of the gauge is similarly inserted into the bore opening and moved back and forth until the gauge is centered. The reading indicates a “minimum” measurement which is the diameter of the hole at the point where it was measured.
Fully electronic bore gauges are now available that read bore openings through the use of transducers to report the readings. Models include units connected to a wired readout and others that use wireless technology. Electronic meters can be manufactured with two or three sensor points to measure accuracy. Some gauges can be modified with extensions to measure greater depths and wider size ranges.
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