Technically simple method for estimating of the ability of metals and alloys to deformation hardening by determining of the hardness gain in the measurement of Rockwell hardness at the bottom of cup from spherical indenter obtained on Brinell instrument is proposed. Using the example of the experimental application of the "two-hardness testers method", difference in the ability to cold-work hardening two austenitic manganese steels is shown. The method makes it possible to evaluate the ability of materials to cold-work hardening without manufacturing of special samples and the use of deforming equipment.