You will probably need to mask it with a circular mask at some point. It will certainly help if you use a canvas larger than the size you want to end up with so that you can mask off the edges. If you find definition lacking try Auto Levels or just manually tweaking the contrast through Image->Adjust->Brightness/Contrast or Curves. Also, highlights can be airbrushed on with a white and Color Dodge mode and shadows with black and multiply. Also, a little manual work might be required on the very center becuase of course Radial Blur has little effect on the center of the blur. I think Alien Skin have filter that emulates this type of brushed metal, but it's more fun to try to achieve it with the tools supplied :)