Abstract: A system for securely placing threaded caps on threaded containers. The system includes a cap feeding device which facilitates the initial placement of caps on container necks. After initial placement, the cap and container are brought into engagement with a spindle assembly which grips the cap and prevents rotation of the container. The spindle assembly engages a is brought into contact with a rotation inducing device, which causes the tightening of the cap onto the container neck. The chuck of the spindle assembly and the rotation inducing device each have the ability to prevent overtightening of the cap onto the container. In addition, the cap and container are specially configured to facilitate initial placement in a manner which reduces the possibility of misalignment.