of the tool adapter 8 the connecting webs 30 31 act as return means 34 35 which provide compensation for the various differences in length that occur as a result of bending of the compression beam 3 during a working stroke and thus counteract associated shifting between the compression beam 3 and the tool adapter 8 effectively preventing the tool adapter 8 from migrating along the compression surface 9 as a result fig3 illustrates another embodiment of a tool adapter 8 fitted with a return element 36 in this embodiment the return means 36 acts between the tool adapter 8 and the compression beam 4 the tool adapter 8 is essentially the same as that of the embodiment described with respect to the previous drawings although it should be pointed out that with this design when the tool adapter 8 is displaced on the compression beam 4 on completion of the compression stroke and hence the bending action due to the different bending lines the return means 36 returns the tool adapter 8 on the compression beam 4 to the original position to this end the tool adapter 8 and or the compression beam 4 have a sliding or rolling means 37 which reduces the friction value in the connecting region in the embodiment illustrated as an example rolling elements are provided between the tool adapter 8 and the compression beam 4 which enable a relative.