How is a wheel profile trued?

A wheel profile is trued using a wheel truing machine, also known as an underfloor wheel lathe or wheel profiling machine, which removes metal from the wheel tread to restore the wheel to its original or specified profile. The wheelset (the wheel and axle assembly) is mounted in the machine, and cutting tools are used to precisely remove material from the wheel tread, flange, and sometimes the wheel back. The machine rotates the wheelset while the cutting tools are advanced to remove the worn or damaged material. The cutting tools are shaped to create the desired wheel profile, ensuring that the wheel meets the required dimensions and tolerances. Wheel truing can be performed with the wheelset mounted on the railcar (underfloor truing) or with the wheelset removed from the railcar and placed in a separate lathe. Underfloor truing is more efficient because it eliminates the need to remove the wheelset from the railcar. Wheel truing is performed to correct wheel defects such as flats (caused by skidding), out-of-roundness, and flange wear. Truing restores the wheel profile, improving ride quality, reducing wheel-rail forces, and extending the life of the wheel. The amount of material removed during truing is carefully controlled to minimize wheel wear and maintain the wheel diameter within acceptable limits. After truing, the wheel profile is inspected to ensure that it meets the required specifications.