Metal lathe boring bars are tools used in machining operations to enlarge or create holes in metal workpieces. They are designed to be used in conjunction with a lathe, which is a machine tool used for shaping and machining metal. Boring bars consist of a long, cylindrical body with a cutting tool attached at one end. The cutting tool typically has a hardened and ground insert made from carbide or high-speed steel. The body of the boring bar is inserted into the lathe's tool holder or tool post, and the cutting tool extends out from the lathe's spindle. The primary purpose of a boring bar is to bore precise and accurate holes with a smooth surface finish. It is commonly used to enlarge existing holes, create cylindrical recesses called counterbores, or create tapered holes called tapers. Boring bars can also be used to machine internal threads by using specialized threading inserts. During operation, the workpiece is securely mounted in the lathe's chuck or collet, and the lathe spindle rotates the workpiece while the boring bar is fed into the hole. The cutting tool removes material by shaving off small chips, gradually enlarging the hole to the desired size or shape. The lathe's feed mechanism allows for precise control over the cutting process, ensuring accurate dimensions and surface finish..

External turning tools are used for machining the external surface of a workpiece. A cutting tool is held in a tool post and the workpiece is rotated on a lathe. As the workpiece rotates, the cutting tool removes material from the external surface to shape it to the required dimensions and finish.

Boring bars are widely used in various industries, such as automotive, aerospace, manufacturing, and engineering, where precise machining of metal components is required. They offer versatility and efficiency in creating or modifying holes in workpieces, making them essential tools in metalworking processes.