Elastokinematic
Quarry Creeper
Im sure someone has already posted this link. I didnt search for it on RCC. Just happened across it a while ago. Its for double threaded rod for making links.
http://www.mcmaster.com/#threaded-rods-and-studs/=d362db
http://www.mcmaster.com/#threaded-rods-and-studs/=d362db