Fiber frequency settings

Is anyone aware of a good description of the relationship between power, speed, and frequency? especially frequency. I am having trouble dialing in my settings mostly because I just don’t know what to change when something is not working. For example, I CANNOT get my settings right on powder-coated tumblers. It’s either too deep and cutting into the metal or not enough to remove the powder coat. I feel like I’m just going in circles because of the three settings that can be changed. I think if I understood better the relationship among the three, I would be better able to problem solve. thanks in advance!