Originally Posted by Nullius
Just use an angle grinder, the edge of the disk will go through it in a couple of minutes. It's noisy and will throw a lot of sparks, but if you've got a good space it should be pretty easy.
"Cycling Plus" tried your technique with a 2005 Kryptonite chain. While trying to cut the links, they wore out some disks. Did not make any progress on the chain links...gave up after ten minutes. Kryptonite uses about three different padlocks with its chains. Depending on which Kryptonite padlock is used, an angle grinder with brand new disks will take six to ten minutes to open the padlock. You might have to replace a disk or two. I'm hoping that Kryptonite will soon upgrade their padlocks to Abus quality. According to "Cycling Plus", their cutting disks just wore out trying to cut the best Abus padlock.
This thread may be helpful to a literate, thoughtful, computer-using crook...if such an thing exists.