How should spindle cone hole diagonally run out of error check?

The lever dial gauge is fixed on the machine tool, so that the dial gauge measuring the top of the head on the inside surface of the spindle cone hole, the dial gauge measuring head is straight on the inside surface of the cone hole, rotate the spindle to check, the reading difference value of the dial gauge is the value of the oblique circle runout error. This inspection method is often used to check the cone hole of the spindle of inner grinding head.