The first precision tool we used was a dial bore gauge. Note the anvils in the foreground. They are used along with a micrometer to preset the exact dimension to be measured. In this case, we used the 4.00-inch anvil and the 0.100 washer and set the dial indicator to zero. A 4.100 bore gauge in a 4.030 bore should swing the gauge 0.070. Get it?