EE WAS ASSISTING MECHANIC HELPING TO REMOVE A SIDE FRAME PIN FROM THE EQUALIZER BAR ON A475 KNOMATSA DOZER. HE WAS HOLDING A BAR AS THE PIN WAS DRIVEN OUT. WHEN THE PIN CLEARED THE BAR SLID IN TO THE BORE OF THE EQUALIZER BAR, WITH THE FRAMEWEIGHT OFF THE EQUALIZER, IT ROTATED UP, TWISTING THE BAR AND PINCHING LEFT THUMB.