Basora, like most ball joints, the joint is comprised of a 'ball & socket' attached to a 'self-locking' taper and a threaded end to pull the taper into a 'very tight seat'. You will not need a hex key for disassembly.

The hex-key socket is used during assembly to keep the taper from turning. Using a common box-end wrench on the nut, and a hex key in the end of the taper, the mechanic begins to pull the taper well into the mating hole in the control arm, and the friction in the self-locking taper will be sufficient that the hex key is no longer required. Final assembly simply replaces the box end wrench with a socket and torque wrench, following BMW's task #31 12 004. Please note, you will need to use a fresh nut upon reassembly.

Your biggest hurdle will be removing the ball joint after you remove the nut. The ball joint will be very tight in that control arm. VERY tight!

BMW shows using a screw style Ball Joint Separator. Please see screen shot photo below. To show the taper, a representative photo of a generic ball joint is shown as well.

best wishes,
Dick

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