I don't know how he did it but i would extrude a cube along a curve the same shape as the groove and then duplicate it around an axis in the center of the disc so they are all in the right place. Then use a Boolean operation to subtract the shape from the disc. I'd also do the holes in the same way.
Originally posted by NitroLiq
Hey Bri, can you go into detail abit on how you created the swirled interior (grooves) with the holes?