Specifications for the Deviation of 3D Reference Axes

In many precision machines and equipment, there are two or three reference axes intersecting at a point theoretically as per the drawing. One example is gyro spin axes construction. The other examples are N/C machine tool spindle axis and table axis as reference axes. Yet another example is the three bevel gear reference axes of space equipment like helicopter, intersecting at a common point. In all the above examples, theoretically the axes have to meet at a common point. But at manufacturing stage one has to specify the acceptable deviation. Presently each axis is measured separately for its straightness or perpendicularity with some surface. Though the axes are measured separately one cannot say to what extent they are meeting or how closely they are approaching to the theoretical intersection point. Further there is no standard to specify this error. The authors have earlier established and published different ways of fitting axis. Some six methods of specifying the deviation/error were also defined. In this paper a method of specifying the error namely Maximum Throat Deviation (MTD) is discussed and an algorithm to compute it is explained.