What are known as bore gauges are measuring devices which are used for establishing the interior size of things such as a hole, cylinder, or pipe. Working in conjunction with a micrometer, a bore gauge will deliver a precise reading of any bore size.

This reading is derived by placing the base of the bore gauge into the opening which is to be measured and then gently moving the base until it perfectly fits the diameter of the opening.

Precision Built

The dial bore gauge base has a fixed point on the one side and a protruding stud on the other which retracts after making contact with the inside wall of the pipe or cylinder.

A spring-loaded centralising mechanism working together with the one fixed and one moving point provide extremely precise measurements.

  • This gauge can have a changeable sized base and can be out to use with a number of opening sizes or they might have compatible extension studs to adjust to the size of the base

Taking a Reading

The user will record the size of the interior diameter of the end of the pipe and selects a base or extension stud of a suitable measurement.

  • By making use of a micrometer, the user can then ascertain the distance between the fixed point and the stud on the base and then take note of the reading.

The readout on the gauge has a bezel which is zeroed to match the size of the base which is being used.

A Positive or Negative Number

The base is inserted into the pipe opening at a small angle and after the base is inside, it is rocked carefully back and forth until the gauge has centred in the pipe.

  • The bore gauge is then withdrawn from the pipe and the measurement on the dial is then read and recorded

The outcome, be it a positive or negative number, is then added to or subtracted from the micrometer measurement to work out the final result.

Traditional and Digital

Some more modern gauges have replaced the older traditional dial by way of a digital electronic display. The electronic readout is adjusted by measuring the base of the gauge.

Any following measurements are then compared to that calibration point.

  • The base of the gauge is then likewise placed in the bore opening and then moved back and forth until the gauge has levelled out.

The readout then displays a “minimum” measurement which is the diameter of the bore at the point where measurement took place.

Greater Depths

Currently available are fully electronic bore gauges which can measure bore openings via the use of transducers to give readings.

  • These newer designs also include devices which can connect to a readout by either a cable by way of wireless technology

These gauges can be made with either two or three sensor points for greater measurement accuracy.