The paper discusses the NC polishing and NC repairing of the arc surface with an ultra-large radius of the paper machine’s press roll. It is very difficult to polish and repair press rolls whose radius is up to several thousands of meters because it is quite beyond the range which a NC system permits. The special NC reconstruction of a machine tool and its principle and method were elaborated. In an example the accuracy of parameters conversion was calculated and related formulas were derived, and also the methods of eliminating errors and the measures to compensate errors were discussed. In view of the abrasion of the grinding (or polishing) wheel, the measure for instantaneous automatic compensation was discussed.