The steel saw is a weaker version of the auto axe, dealing roughly half as much damage. It appears to be a modified concrete cutter or concrete saw, with a rotating metal blade. Slaves use the steel saw for cutting through metal objects. However, this does not translate to an in-game damage bonus against robots.
A chance to loot this item occurs during the slave revolt: several slaves will die, and some may have this weapon on their bodies.
Can be found on Adan's body, near the bus, during the slave revolt.
You can get one by killing Brand near the ammo press in the mill but you'll lose karma, you'll have to hide from other slaves and slave masters, and a certain slave will stay hostile until you use a Stealth Boy although she seems to have an incredibly low Perception so she's not very dangerous.