We have considered **the steel grinding balls surface hardness measurement **in the last article. Remind, we have conducted 4 hardness measurements during the hardness determination: three test measurements on vertices the imaginary equilateral triangle and one control measurement in the center of this triangle.

We will considered the steel grinding balls hardness measurements at 1/2 radius depth in this article. This measurement conduct for confirmation grinding balls to the 4th hardness group (DSTU 8538:2015).

The steel grinding balls hardness at 1/2 radius depth determines on one flat surface area prepared in accordance to GOST 9012 and GOST 9013 requirements by removing the ball metal to the required depth.

It is necessary remove metal to 1/2 radius distance at each side of the grinding ball, in order to the sample stably stood on hardness tester table.

At 1/2 radius distance performs four hardness measurements on two mutually perpendicular lines drawn with a pencil, the measurement points should correspond to 1/2 radius of the grinding ball.

The minimum and the maximum hardness values ignore, and the hardness defined as arithmetic average value of the other two dimensions