<p>Cooling lubricants (CL) are used in various machining processes. In addition to heat dissipation, influencing the tribological system is a key function. In particular, the thermomechanical load on the cutting wedge is influenced by a change in friction in the secondary shear zone. In addition to tribological effects, the mechanical forces of the fluid jet have a significant effect on chip formation, particularly when a high-pressure supply of CL is used. However, investigating the mechanical effect of CL on chip formation is challenging due to poor accessibility of the chip formation zone. Using a planing test rig and a high-speed camera, it is possible to show that the mechanical force of the CL supply reduces the chip curvature radius and influences deformation of the chip during machining. In particular the force of the CL-jet force in cutting normal direction has a significant effect on reducing the chip curvature radius.</p>