A surgical robot tool has a thread driver 66 for driving suture thread 65 from a thread holder 64 through the hollow lumen of a needle 63 at an end effector 62 disposed at a distal end of an elongate hollow shaft 60. The thread passes between a friction pad 69 and leaf spring 70 in a hollow member 60 with a flag 71 driven by a drive tab of a robot arm to pay out the thread in one direction, preferably during insertion and withdrawal of the needle during suturing operations. The robot arm has an interface fastening structure for attachment to different surgical tools and a drive mechanism with extending linkage configured to provide mechanical drive to the flag 71 of a tool fastened to the arm interface.
