Originally Posted by GAMEOVER
Originally Posted by willwren
Those obviously WEREN'T hardened rotors.
you can drill through anything will
remember i deal with metal everyday
with a carbide drill you can drill through hardened material
also there are different degrees of hardness
and process to make material more harder than others
Wire EDM is the preferred method of drilling or machining hardened materials, particularly when you get to the RC 58-60 range or harder in steels. However.......
Then you know all about stress cracks in hardened materials. You weaken the rotor by drilling after hardening, and even somewhat STILL if you drill before hardening. The holes need to be CAST into the blanks to prevent stress cracks (before hardening) to be suitable fore everyday street use, and still provide no real benefit to you other than looks, and decreasing the surface area 'bite' that the pads can achieve. Crossdrilling will in effect REDUCE your ability to brake.
Slotting, however, has proven benefits, and doesn't cause the stresscracking problem. Slots allow the pad to outgas, preventing a gas layer from being trapped in between the pad and rotor (imagine an air hockey table.....same effect). Slotting also allows water to escape, further improving wet braking, and allows pad friction material to be effectively removed from the rotor.