There is one suitable alternative to a telescopic gauge, called a dial bore gauge. This can be used for exactly the same roles as a telescopic gauge and has many similarities, with two anvils that gauge the diameter of a bore. It needs to be calibrated before it is used. Calibrating involves checking the accuracy of its reading against a known measurement and adjusting the gauge if necessary. A telescopic gauge in comparison relies on a user’s accuracy for every reading.
A dial bore gauge is twice the price of a telescopic gauge. It’s a sensible option if you are going to be measuring bores frequently as the read-out is given on the dial, with no secondary measuring (apart from initial calibration).
