[Joe Johnson]

It is hard but if you are careful and go back and forth and back and forth you can make the standard chain breaker the OP discussed work but it is definitely a "you have to be patient and you have to develop the knack" type skill.

SO... ...of late, my chain breaker of choice is a Dremel. Seriously. If you take a paint pen and mark the link that needs to be cracked (which you should probably get in the habit of doing anyway) and then you get that link clamped in a vise and then grind off the pins (and part of the plate), you can use a screw driver to pop off the plate and then you're in business.

It ain't elegant but you get a nice clean cut with no risk of damaged chain going back on your robot.

YMMV.

Dr. Joe J.