6.3 Rail milling issues
When a rail is milled, the milling cutters have been pre-set to establish a specified transverse profile. It is therefore both more difficult than with other reprofiling techniques to vary the profile and also more difficult to establish an “incorrect” profile, unless the specified profile is itself incorrect.
Individual milling cutters create a characteristic finish of small, uniform irregularities which wear out under traffic. In extremely noise-sensitive locations these are sometimes removed with longitudinal “shuffle-block” grinding. Small chips of swarf result from milling.