These are a range of gauges that are used to measure a bore's size, by transferring the internal dimension to a remote measuring tool. They are a direct equivalent of inside calipers and require the operator to develop the correct feel to obtain repeatable results.Twisting the knurled end of the handles locks the gauges; this action is performed to exert a small amount of friction on the telescopic portions of the gauge (the smaller diameter rods found at the T head of the gauge). To use, the gauge is inserted at a slight angle to the bore and gently locked to a size slightly larger than the bore while at that angle. Then, rocking the handle side-to-side, slowly move the handle across the bore to the other side. The rocking will first align the gauge with the bore axis and the act of moving the handle to the other side of the bore will bring it to the exact bore diameter. This action compresses the two anvils where they remain locked at the bores dimension after being withdrawn.Dial Bore GaugeFEATURESSmall bores from 10mm to 18mm.Highly versatile 18-50mm bore gauge covers a large range for which one needs to generally purchase 2 bore gauges having ranges ? 18-35mm and ? 35-60mm.The third bore gauge covering a range of 50-150 mm, is widely used in Automobile, Aircraft, Engine and Pump manufacturers.High wear resistance due to carbide-tipped stationary and moving anvilsExtra wide bridge ensures automatic centering in the bore. Self- centralizing feature of this bore gauge ensures that the measurement can be done with minimum of skill.Furnished in a sleek wooden case containing measurement anvils and extension rods with necessary tools.SPECIFICATIONSupplied with interchangeable anvils in different sizes. The Dial indicator is fully protected by a rugged cover. Packet as a set with all necessary accessories to ensure the complete range.