A bore gauge refers to a set of tools used for accurately measuring bores or holes. An essential tool for engineers and machinists to have in their toolbox, a bore gauge comes in a variety of forms and sizes and are used in different applications. 

The various types of bore gauges include dial bore gauge, telescope bore gauge, small hole gauge, beam bore gauge and dial bore gauge. Typically made of steel, these precision instruments are used within micrometres.

You can find various forms of gauges for different levels of accuracy. For instance, expanding gauges are used for a more accurate measuring solution, while solid gauges are used for basic levels of measurements. Usually made up of one or two anvils, these gauging devices can be inserted into a hole and evaluated after removal to determine the exact diameter. The accuracy of your measurements will always be assured with this gauge paired with a precision calliper.

How to use a bore gauge?

Let us take a look at the steps to read measurements using a dial bore gauge:

  • Put the bore gage inside the micrometre and rotate the dial until the pointer points at the zero mark of the dial face.
  • Then place the dial gauge in the bore you want to measure. Make sure that the anvils touch the sides of the bore.
  • Gently move the bore gauge back and forth without disturbing the anvils. The pointer will swing clockwise or counter-clockwise. 
  • At a particular point, the pointer will start to reverse itself and move in the opposite direction towards the zero mark. 
  • Record the precise measurement when the pointer starts heading towards zero.
  • Now you need to add or subtract the recorded value from the target number the indicator was calibrated to. Let’s make the calculation easier with an example. Imagine the bore gauge’s indicator was zeroed to 4 inches and the pointer changed direction at the 0.009 inches marking on the dial face, the final measurement of the hole is 4.009 inches. On the other hand, if the pointer moved counter-clockwise and changed 0.009 inches to the left, the final measurement of the hole is 3.991 inches.

What mistakes do you need to avoid when using bore gauges?

Never drop or mishandle a bore gauge: Bore gauges are precision instruments. If they are dropped or damaged while operating, the calibration may change and you will get an error while measuring.

Never use a damaged dial bore gauge: Once damaged, either give it for repair or replace it. As mentioned earlier, a damaged gauge could give incorrect data.

Do not forget to zero the gauge: Failing to zero the gauge after usage could also lead to wrong measurements.

Not storing the gauge components properly: Always store the gauge in an internally lined storage case.

Not maintaining the gauge properly: The bore gauge should be kept in a good and clean condition.

Not keeping the work area clean: Similarly, the work area should not be cluttered, slippery or dirty. It is better to wear nonslip shoes while using a bore gauge.

Avoid storing at extreme temperatures: Ideally store the dial bore gauge at room temperature.

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