A method for determining part wear, such as using a wear metric, includes receiving, from a sensor, sensor data representing a surface of a wear part. The method further includes determining distances between measured points in the sensor data and points on one or more part models, which part models may include new part models and/or worn or wear limit part models. The method further includes using a bounding model that at least partially envelopes the part model(s) and the measured points to determine a direction along which the distances are measured. The method may also include quantifying wear using the measured distances.