Our O1 precision-ground tool steel square bar is an oil-hardening alloy that offers superior machinability and a reliable response to heat treatment. These bars are commonly used for manufacturing complex dies, guides, and precision mechanical parts in tool and die shops. The precision-ground finish provides a clean, flat surface that ensures your layout and machining are as accurate as possible. O1 tool steel is prized for its versatility and its ability to achieve a very high level of hardness with minimal risk of cracking. Onlinemetals.com stocks precision-ground O1 square bars to help you achieve the highest quality in your custom fabrications.