Abstract: A method of measuring the internal taper (Miu) of an internally upset tube is disclosed along with the apparatus for practicing the method. The apparatus includes a first link mechanism that is operated to move a plurality of locating arms outwardly to a position near the inner wall of the tube. The locating arms are moved into the taper until the forward end of each arm is deflected toward the center of the tube far enough to pivot the other end into engagement with the tube and stop further movement of the first link mechanism. A second link mechanism is moved toward the outer end of the taper until it engages the taper adjacent its outer end. The distance between a reference joint on the first mechanism and a reference joint on the second is approximately the length of the taper.