Machining opposite surfaces of a workpiece to be parallel to one another

A method of machining two opposite surfaces of a workpiece, comprising:

• providing three edge features along one or more edges of a workpiece, said one or more edges disposed between a first face of the workpiece and a second face of the workpiece, said second face being opposite the first face;
• mounting the workpiece in a first fixture having a first fixture base and a first set of three fixture points disposed on a surface of the first fixture base, said first set of three points being sufficiently elevated above the surface of the first fixture base to ensure that the workpiece does not contact the surface of the first fixture base;
• performing a first machining operation on the first face of the workpiece;
• dismounting the workpiece from the first fixture;
• re-mounting the workpiece to in a second fixture having a second fixture base and a second set of three fixture points disposed on a surface of the second fixture base, said second set of three points being sufficiently elevated above the surface of the second fixture base to ensure that the workpiece does not contact the surface of the second fixture base;
• and
• performing a second machining operation on the second face of the workpiece.

A fixturing system for supporting a workpiece for machining two opposite surfaces of the workpiece to be parallel to one another, said system comprising:

• a first fixture having a first base and having a first set of at least three fixture points disposed on a surface of the first base, said first set of at least three fixture points being arranged on the first base to support a workpiece in a first predetermined orientation above the surface of the first base and to engage corresponding at least three edge features disposed around a peripheral edge of the workpiece;
• and
• a second fixture having a second base and having a second set of at least three fixture points disposed on a surface of the second base, said second set of at least three fixture points being arranged on the second base to support the workpiece in a second predetermined orientation above the surface of the second base and to engage the at least three edge features disposed around the peripheral edge of the workpiece;
• said workpiece has a top face and a bottom face opposite the top face, the peripheral edge extending around a periphery of the workpiece between the top face and the bottom face;
• wherein:
• when the workpiece is supported in the first fixture, the top face of the workpiece is oriented for performing a first machining operation on the top surface of the workpiece;
• and
• when the workpiece is supported in the second fixture, the bottom face of the workpiece is oriented for performing a second machining operation on the top surface of the workpiece.