Padlock pre-assembly machines add all components required prior to the pinning process. Depending on the design of the padlocks, the machines insert plugs (barrels) together with anti-pick plates and plug retainer pins into padlock bodies. The machines also install shackles with shackle springs and retainer pins and all locking bolts with springs. Vibratory feeder bowls feed all components with the exception of the padlock body and the shackle, which are fed from a magazine stack. The assembly is automatically unloaded into a chute. An operator is required to maintain levels of components in the two magazine stacks.