An apparatus configured to measure a thread profile of an internally threaded surface of an object, the internally threaded surface comprising a plurality of crests in the longitudinal direction of the internally threaded surface, the apparatus comprising: a support extending longitudinally from the apparatus, the support comprising at least two distal contact surfaces, distal to the apparatus, and at least two proximal contact surfaces, proximal to the apparatus, wherein the at least two distal contact surfaces and the at least two proximal contact surfaces are separated by a space and are configured to register to at least four contact locations on the internally threaded surface of the object including at least two longitudinally spaced contact locations on the internally threaded surface; two external contacts configured to make physical contact with an external surface of the object; at least one motion stage configured to controllably move an optical head along a measurement axis over the internally threaded surface, wherein the measurement axis is substantially parallel to a line drawn through the thread crests of the internally threaded surface, the optical head comprising: (i) an emission optical element in optical communication with a first light source configured to emit a first incident light beam onto the internally threaded surface to generate scattered light off of the internally threaded surface at a measurement point; and (ii) a detector optical element in optical communication with a first detector configured to receive at least a portion of the scattered light from the measurement point, and wherein the first detector is configured to output a detector signal indicative of the intensity and the position of the received scattered light, and a computer configured to transform the detector signal into a measurement of the distance from the optical head to the measurement point. a support extending longitudinally from the apparatus, the support comprising at least two distal contact surfaces, distal to the apparatus, and at least two proximal contact surfaces, proximal to the apparatus, wherein the at least two distal contact surfaces and the at least two proximal contact surfaces are separated by a space and are configured to register to at least four contact locations on the internally threaded surface of the object including at least two longitudinally spaced contact locations on the internally threaded surface; two external contacts configured to make physical contact with an external surface of the object; at least one motion stage configured to controllably move an optical head along a measurement axis over the internally threaded surface, wherein the measurement axis is substantially parallel to a line drawn through the thread crests of the internally threaded surface, the optical head comprising: (i) an emission optical element in optical communication with a first light source configured to emit a first incident light beam onto the internally threaded surface to generate scattered light off of the internally threaded surface at a measurement point; and (ii) a detector optical element in optical communication with a first detector configured to receive at least a portion of the scattered light from the measurement point, and wherein the first detector is configured to output a detector signal indicative of the intensity and the position of the received scattered light, and (i) an emission optical element in optical communication with a first light source configured to emit a first incident light beam onto the internally threaded surface to generate scattered light off of the internally threaded surface at a measurement point; and (ii) a detector optical element in optical communication with a first detector configured to receive at least a portion of the scattered light from the measurement point, and wherein the first detector is configured to output a detector signal indicative of the intensity and the position of the received scattered light, and a computer configured to transform the detector signal into a measurement of the distance from the optical head to the measurement point.