RE: Cutting Aluminum spinners....best tool?
First measure and mark what you want cut! Measure again to make sure both cutouts are marked the same. Measure again to make sure the first measurement was right. Measure one last time to be sure the double check was right. You can't get it right by eye.
When you cut, plan your cut ahead of time. Don't cut all the way to the line. Always leave the line. The line is your friend, don't destroy him. I use a cutoff wheel at this point to do the rough cutting. Cutoff wheels and lines don't get along. The cutoff wheel will ruin all your careful measuring and marking. Just get it close. You'll clean it up later. Don't run the cutter too fast and let it get away from you or it'll be mean to your line.
Switch to a sanding drum. The sanding drum is much friendlier to your line. Go easy and right up to the line, again leaving the line. Try to get an even amount left all the way around. On the last pass bring it as close to the line as you can.
Be sure to balance it after you're done.
Dave