The invention relates to a device for a clamping tool for applying pressure to a workpiece. 
Furthermore, the invention relates to a clamping tool. 
An example of a clamping tool comprising a device for applying pressure to a workpiece is a screw clamp wherein a spindle acts upon a workpiece by means of a device for applying pressure to a workpiece. 
From DE 18 47 400 U1, there is known a clamping device which has a pressure-exerting piece that ends in a ball.  Furthermore, there is provided a pressure plate which is fixed in removable manner to the ball of the pressure-exerting piece.  A spring is provided as the means for the removable attachment of the pressure plate. 
From DE Patent 929 357, there is known a screw clamp comprising mounting devices which are arranged on the two pressure plates and are in the form of rotary bearings for exchangeable and rotatable pressure pads which serve as work-piece supports.  The rotary bearings of these pressure pads are in the form of pushbutton bearings. 
From DE 74 02 870 U1, there is known a clamping tool comprising a threaded spindle and a pressure cap.  The pressure cap encloses a head of the threaded spindle with a footstep bearing in positive manner.  A spring or a snap ring forms the edge of the step bearing. 
From DE 197 51 599 A1, there is known a screw cramp which has a pressure plate that is fixed on a threaded spindle in pivotal manner.  The pressure plate can be aligned linearly by means of an adjusting device and arrest a spindle on an upper surface of a sliding arm. 
From U.S. Pat.  No.  3,052,462, there is known a C-clamp incorporating a screw, wherein the screw carries a ball head.  A push button is seated on the ball head.  This push button has a boring and a ring-like groove by means of which there is defined a lip which is connected by a neck to the rest of the body of the push button.