A braking and/or clamping device for a shaft which is guided relative to a main body, having an actuating assembly and a shaft coupling assembly (80, 100, 120), - wherein the actuating assembly has a split housing, which has an attachment zone and a bending zone which can bulge elastically in some regions and has two bending plates (15, 16) spaced by a pressure space, - wherein the bending plates (15, 16) each have jaws (23, 24) in two mutually opposing clamping zones, said jaws having friction faces (31, 32) with surface normals pointing inwards, - wherein there is a sealed pressure space between the bending plates (15, 16) and at least one supporting element, which sealed pressure space can be filled with a pressure medium in order to push the friction faces (31, 32) apart elastically, - wherein the shaft coupling assembly (80, 100, 120) has a coupling region which has two mutually spaced friction faces (91, 92) with surface normals pointing outwards, - wherein the shaft coupling assembly (80, 100, 120) has a flange region via which it is arranged on the shaft either directly or indirectly via a clamping mechanism, and - wherein, when the pressure space is relieved of load, the friction faces (31, 32) of the actuating assembly are applied to the friction faces (91, 92) of the shaft coupling assembly (80, 100, 120), providing the clamping and/or braking force, characterised in that - at least one deformation measurement means is arranged in the transition region between the attachment zone and the bending zone, - each bending plate (15, 16) has an axial groove (17, 18) from the pressure space in order to support at least one supporting element, and - the shaft coupling assembly (80, 100, 120) has a slotted or multiply split ring as the brake disc (81, 101, 121). - wherein the actuating assembly has a split housing, which has an attachment zone and a bending zone which can bulge elastically in some regions and has two bending plates (15, 16) spaced by a pressure space, - wherein the bending plates (15, 16) each have jaws (23, 24) in two mutually opposing clamping zones, said jaws having friction faces (31, 32) with surface normals pointing inwards, - wherein there is a sealed pressure space between the bending plates (15, 16) and at least one supporting element, which sealed pressure space can be filled with a pressure medium in order to push the friction faces (31, 32) apart elastically, - wherein the shaft coupling assembly (80, 100, 120) has a coupling region which has two mutually spaced friction faces (91, 92) with surface normals pointing outwards, - wherein the shaft coupling assembly (80, 100, 120) has a flange region via which it is arranged on the shaft either directly or indirectly via a clamping mechanism, and - wherein, when the pressure space is relieved of load, the friction faces (31, 32) of the actuating assembly are applied to the friction faces (91, 92) of the shaft coupling assembly (80, 100, 120), providing the clamping and/or braking force, characterised in that - at least one deformation measurement means is arranged in the transition region between the attachment zone and the bending zone, - each bending plate (15, 16) has an axial groove (17, 18) from the pressure space in order to support at least one supporting element, and - the shaft coupling assembly (80, 100, 120) has a slotted or multiply split ring as the brake disc (81, 101, 121).