Telescopic gauges are used to measure the internal diameter of a bore, hole or groove up to 150mm (6″) in diameter, for example camshaft bearings or connecting rod bore bearings.
They are primarily used by mechanics measuring the bore size of a crankcase in an engine where the pistons move up and down.
Mechanics need to measure the bore in a crank case as the piston head and the cylinder must match perfectly to stop any unwanted escape of fuel or power, causing the engine to malfunction.Measuring the diameter of the bore enables them to check that the piston head will fit perfectly.
In many cases, telescopic gauges are used where the hole or bore is too small for a vernier calliper or internal micrometer to fit.
