First time repair M8x1.25 rocker arm. The special step core drill included will not bind on the slotted area at the top of the hole which would normally snap any 2 flute drill when drilling by hand. The core drill will allow a special 11.7mm length no flange insert P/n 18125117N to be installed deeper than the standard kit. The largest diameter of the step drill is .380 inches or 9.7mm.  Some detail notes on the type of repair. Instructions