The internal taper gauge measures the largest diameter of a conical bore or a conical keyway. An IKT replaces previous slower and more expensive gauging methods.. Internal taper gauge (IKT). Direct gauging of major diameter of internal tapers or tapered slots. Models with 60°, 90° and 127° taper. Application range: Ø 0.5 mm to 120 mm. Measuring range: 11.5 mm for 60° taper19.5 mm for 90° and 127° taper.