This paper considers the problem of wear estimation in a standard industrial robot joint. Motivated by the observation that the wear processes in a robot actuator cause an increase of the friction levels in the joint, static friction observations are used to infer the wear levels. An existing static friction model is extended to include the eects of wear, which are analyzed and modeled. The resulting model can explain friction in a robot joint with respect to changes in speed, load, temperature and wear. Based on this model and a test-cycle that generates static friction observations, a modelbased wear estimator is proposed. The performance of the estimator is found both by means of simulations and experiments on an industrial robot. As it is shown, the method can distinguish the eects of wear even under large temperature variations, opening up for the use of robust joint diagnosis for industrial robots. Abstract: This paper considers the problem of wear estimation in a standard industrial robot joint. Motivated by the observation that the wear processes in a robot actuator cause an increase of the friction levels in the joint, static friction observations are used to infer the wear levels.An existing static friction model is extended to include the effects of wear, which are analyzed and modeled. The resulting model can explain friction in a robot joint with respect to changes in speed, load, temperature and wear. Based on this model and a test-cycle that generates static friction observations, a model-based wear estimator is proposed. The performance of the estimator is found both by means of simulations and experiments on an industrial robot. As it is shown, the method can distinguish the effects of wear even under large temperature variations, opening up for the use of robust joint diagnosis for industrial robots.