A crank-operated packer mechanism includes crank pins and crank arms assembled by a tapered spline connection. The connection includes tapered spline features on outer ends of the crank pins and in openings provided at outer ends of the crank arms, which interlock when the crank pins are inserted in the openings. The connection further includes a locking feature for locking the connection, such as a locking nut screwed onto a threaded outer end of the crank pins when inserted into the opening. Fixing of rotary bearings onto the crank pins is done by a fixing nut which at the same time serves as a disassembling aid for the spline connection. The crank arms are shaped in a way that deviates from a straight shape to such an extent that the crank shaft is statically balanced about its central rotation axis. Also a baler including the aforementioned packer mechanism.