ARB RD99 - Manual (Page 14)

3 Installing the Air Locker
12
3.3 Drilling and Tapping the Bulkhead Port
An airline port must be drilled and tapped through the third member
casting to mount the bulkhead fitting into.
Mark a spot on the third member casting in the position shown in
the completed assembly in Figure 5.
Figure 5.
Remove the pinion shaft assembly from the third member.
Press the pinion support bearing out of the third member.
Drill through the housing square to the outside surface using a
11.2mm [7/16”] drill.
Tap the hole from the outside using a ¼” NPT pipe tap.
Remove any sharp edges from the hole that may chip-off and fall
into the housing.