What is the main function of the carriage on a lathe?

The carriage on a lathe primarily serves to support the cutting tool and allow it to slide along the ways of the machine. This functionality is crucial because it enables the tool to move precisely along the length of the workpiece, facilitating accurate shaping and machining operations. As the carriage moves, it can engage with the workpiece to perform various operations, such as turning, facing, or boring, depending on the setup of the lathe.

The design of the carriage ensures stability and precision as it travels, which is essential for achieving desired tolerances and surface finishes in the machined parts. By enabling both longitudinal and cross motions, the carriage plays a pivotal role in the overall operation of the lathe, ensuring that the cutting tool can operate effectively across the entire surface of the material being worked.

The other options describe functions that are not primarily performed by the carriage. For instance, holding the workpiece is the function of the chuck or other workholding devices, providing power is typically the role of the motor, and controlling coolant flow involves a separate coolant system that maintains tool and workpiece temperature during machining.