Aluminum Trim Questions

Hello All Again.
I noticed in some of the posts you guys mentioned "ripping down" the alum. trim to a certian size. Excatly how does one go about that since it's aluminum.
If you use tin snips, it would leave an uneven edge.
Also, what is the optimum "thickness" for angle or "T" trim to be able to bend it around cuves (not sure how to spell RADI ?) 1/4", 1/8", 1/16", etc.
thanks,
Bob
I noticed in some of the posts you guys mentioned "ripping down" the alum. trim to a certian size. Excatly how does one go about that since it's aluminum.
If you use tin snips, it would leave an uneven edge.
Also, what is the optimum "thickness" for angle or "T" trim to be able to bend it around cuves (not sure how to spell RADI ?) 1/4", 1/8", 1/16", etc.
thanks,
Bob