A tooling mandrel for use in assembling a disk drive having a disk drive base and a head stack assembly with a pivot bearing cartridge. The cartridge includes a shaft and a sleeve. The shaft includes a shaft first end with an engagement feature. The shaft defines an axis of rotation and a shaft outer circumferential surface. The sleeve defines a sleeve inner circumferential surface disposed towards the shaft outer circumferential surface. The tooling mandrel includes a retainer element defining a longitudinal axis and including a distal end. The distal end engages the engagement feature. The tooling mandrel includes tooling fingers angularly fixed to the retainer element with respect to the longitudinal axis. The tooling fingers each include a tip portion. Each tip portion engages the pivot bearing cartridge through cooperative radial movement with respect to the axis of rotation with the distal end engaged with the engagement feature.