With the bottom washer on the shaft drill a 5mm hole just above the washer through the centre of the shaft as shown in the picture. Once you have drilled through to the other side slide the bolt back into the hollow shaft. Mark the bolt with a marker or the drill. Remove the bolt and drill a 4.5mm hole through the centre. Tip: grind a small flat on where you want to drill the hole on the bolt to stop the drill bit slipping on the round surface.
