If you need to really crank up the tensioning order for the blades to clip, the likely cause is that the tension set has become worn and needs to be replaced if you have an A2 clipper. These can be ordered with next working day delivery from us here.For older clipper models with a Heiniger style clipper head, this can happen when the tension screw has not been loosened before swapping the blades or that the blades are not quite aligned properly. Contact us for support here.