Methods of machining turbine components using a reference surface

A method of repairing a turbine blade that includes a tip shroud and a first pre-sintered preform (PSP) attached to the tip shroud, the method comprising:

• positioning the turbine blade within a system including a machining tool;
• determining a first distance between a surface of the first PSP and a datum surface formed in the tip shroud;
• removing the first PSP from the tip shroud;
• coupling a second PSP to the tip shroud;
• and
• machining a surface of the second PSP using the machining tool, wherein machining the second PSP surface comprises controlling movement of the machining tool using the datum surface as a reference, such that the machined second PSP surface is located the first distance from the datum surface.