Lock Cylinder Non-Functional

Disconnect the negative battery cable.
Deactivate the supplemental restraint system (SRS), see DISABLING & ACTIVATING AIR BAG SYSTEM .
Remove the steering wheel; see STEERING WHEEL REMOVAL/INSTALLATION .
Twist off the cap from the lock cylinder.
Use a 1/8-inch diameter drill bit to drill out the lock cylinder retaining pin.
Use a 3/8-inch diameter drill bit to drill down the middle of the ignition lock key slot until the ignition switch lock cylinder breaks loose.

Fig 1: Locating Drilling Diameter
Courtesy of MAZDA MOTORS CORP.
Remove and discard the lock cylinder and drill shavings from the steering column.
Remove the bearing retainer (1), bearing (2) and gear (3). Thoroughly clean all drill shavings from the steering column and inspect it for damage.

Fig 2: Removing Bearing Retainer, Bearing And Gear
Courtesy of MAZDA MOTORS CORP.
NOTE:
- Use a new lock cylinder.
Install in reverse order of removal.
Verify lock cylinder operation.