As a child, Samuel "Starr" Saxon was always fascinated by robots. When he was fourteen years old, he stumbled across one of Doctor Doom's Servobots, which had been destroyed by the Fantastic Four. He used the pieces of the Servobot to create his own automaton. He was soon threatened to lose his creations by his mother, who thought of his passion for robots unhealthy. Starr murdered her and made it look to be a laboratory accident, collecting the insurance money. Years passed, and Starr became noticed by the Tinkerer, who took him under his wing. He created a cyborg assassin, which battled Daredevil. Although he lost, Starr developed a zeal for battling the super hero, and took the guise of Mr. Fear. During the battle, Starr fell from his hover platform and died. However, the robots he had stationed around him rescued him, encoding the entire contents of his brain onto a computer. When he awoke, he was in the body of a cyborg.

Taking the name Machinesmith, Starr created various drones to sell, including a Magneto robot, which battled the X-Men on several occasions until destroyed by Sentinels. His robots also briefly battled the Thing and Jack Of Hearts. Later, Machinesmith used Dragon Man to battle Captain America. After numerous battles with super heroes, Machinesmith grew saddened over the loss of his former body and being stuck in a cyborg. Due to his programming, he could not end his existence, so he had Captain America do it unknowingly. Captain America succeeded in destroying Machinesmith's consciousness. However, soon after, he was revived by one of his cyborg bodies. He had an epiphany and found that living as a cyborg was far superior to organic life.

Machinesmith was eventually contacted by Red Skull, who invited him to join him in the Skeleton Crew. Alongside the Skeleton Crew, Machinesmith fought the Avengers several times, and developed a romantic obsession with Vision. Machinesmith also served briefly as Iron Man's aide, though the stint was short-lived. Upon the apparent death of the Red Skull, Machinesmith attempted to destroy the world by nuclear holocaust, but his plans were thwarted by Captain America.

After the Skeleton Crew disbanded, Machinesmith joined the Masters Of Evil, under the Crimson Cowl's leadership. The team was subsequently defeated by the Thunderbolts and disbanded. Most recently, Machinesmith created a techno-organic virus. The New Warriors were sent to stop him, though they proved to do little against Machinesmith.