Visually, both ball pressure screws and spring plungers look just like grub screws with a ball bearing fixed on the end but they are very different in function.
Ball pressure screws are designed to apply pinpoint pressure to a part in a clamping application. The steel ball channels the applied pressure creating a positive holding result.
Ball pressure screws are offered in versions such as round ball pressure screws and flattened ball pressure screws, which are also available with smooth or serrated surfaces.
Spring plungers look similar but unlike ball pressure screws where the ball is fixed, the ball in a spring plunger is spring loaded to enable release at certain pressures.
Spring plungers are known as spring loaded devices (SLDs), and are also described as devices that enclose a spring within a threaded capsule.
Ball pressure screws are typically used in jig and fixture applications where the operator needs to achieve a high clamping force in limited space. The hardened ball end, while achieving positive clean holding is also less likely to damage the workpiece being held.
The variations available are many ranging from grub screw-type headless to socket cap screws.
The ball end can be constructed from steel, stainless steel or Delrin.