When machining rotors, what is the reason for setting the indexing collars to zero?

Setting the indexing collars to zero when machining rotors is essential for accurately knowing how much metal has been removed from each side of the rotor. This practice is crucial because it helps the machinist monitor the reduction in material thickness, ensuring that each side of the rotor is machined evenly. This information is vital for maintaining proper rotor balance and ensuring optimal braking performance. If the amount of material removed is not known, there could be inconsistencies that may lead to uneven wear or potential safety issues when the rotor is used in the vehicle.

In this context, while determining the proper cut speed, measuring groove depth, or ensuring that cuts are even are relevant aspects of machining, they do not directly address the primary purpose of setting the indexing collars to zero. Proper depth measurement and evenness can also be outcomes of achieving accurate metal removal, but the core reason directly relates to tracking the amount of material being machined.