clifto writes:

Dremel also makes a fiberglas cutoff disc. Somewhat more expensive than
the thin quarter-sized ones in the tube, but they last a LOT longer and
work a LOT better. I've never had one fly into pieces yet, though it
doesn't seem impossible.

Those are also several times as thick as the thin Dremel ones, so it
will take longer to cut through whatever you're cutting (since the power
available from a Dremel tool is rather limited).

This still sounds like a good idea for anything as thick as a padlock
shackle, since it will be difficult keeping the really thin disc
perfectly aligned with the slot for the duration of the cut. The thin
disc breaks really easily if it gets twisted in a slot that it is
cutting.

Dave