# How The Ball Bar Checks the Squareness of a C.M.M.

The first step is to incline the ball Bar at about 45 degrees.

• Place the Heavy Duty Stand holding the Ball Bar on the C.M.M. table, with the Ball Bar pointing at right angles to the X axis.
• Measure the Ball Bar. Reverse the Ball Bar about 180 degrees and measure it again.
• The difference in the two measurements is the squareness error of the Z axis to the X axis.
• Place the inclined Ball Bar at right angles to the Y axis.
• Measure the Ball Bar.
• Reverse the position of the Ball Bar about 180 degrees and measure it again.
• The difference in these two measurements is the squareness error of the Z axis to the Y axis.
• Place the Ball Bar horizontal and point it along one of the body diagonals. Measure the Ball Bar.
• Point the Horizontal Ball Bar along the other body diagonal and measure it.
• You have just measured the squareness of the X axis to the Y axis.

A full Ball Bar setup, for a medium C.M.M. costs less than one thousand dollars!

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