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From: ------
From: ------
Gary,
The Taylor Principle, also called the Envelope Principle, defined within ASME Y14.5M - 1994 by rule #1 states that the limits of size of a feature prescribe the limits within which the size and form (deviations due to bending. warping etc..) are allowed. For example if you have a simple block with a width defined as .750 +/- .010 the block must not exceed a boundary of .760 due to size and form. Extending our analysis, if the block is produced at size of .750 then the overall bend of the block cannot be greater than .010. .750 +.010 = .760 . There is no boundary requirement for a feature of size at LMC (Least Material Condition). From a design perspective the Taylor principle is most applicable for features that must mate or clear another feature. For example, If you are designing a shaft to fit into a bearing than the Taylor principle is very important. If the bearings internal journal is defined as .750 +/- .001 MMC= .749 than the mating shaft might be designed as a line fit say, .748 +/-.001. giving the allowable boundary to be .748+ .001 = .749. so, if the shaft is manufactured at .748 then it can bow or warp .001. As you can see the Taylor principle would protect the design intent and allow the parts to assemble. For most non-mating applications a relaxation of the Taylor principle is a good idea in that production costs are reduced.
There are many excellent books that describe the Taylor Principle in more detail please contact me at www.engineersedge.com/GDT_Training.htm for recommendations.
Kelly Bramble