I'm being asked to attempt to tolerance the right side of a cylindrical dia. with a +- tolerance of .003 and the left half of the cylindrical feature with a tolerance of -.002 smaller than the right diameter measures.
The reason I was given was based on manufacturing processes & part functional needs where a lathe tool is known to cut from center of the cylindrical length in both directions BUT the part if it has a seam from the tool must be equal to or smaller on the left half as compared to the right.
Thank you Kelly.
Much appreciated. Not far off what I was recommending to the engineer--flagging with a drawing note and explanation.
Here's what the engineer really wants.
X is being used as a variable for our discussion purposes, we're not intending to dimension anything this way on a print.
To explain the illustration--don't think of this as my drawing in it's proper dimensioned state, it is for this discussion.
I've assigned the variable "X" to the right side of the part diameter dimensions .265 +- .003
The engineer wants the left side to be a mathematical < (less than) situation using the actual measured value of the right side diameter for a nominal with a -.002 allowed tolerance.
So if the part were to measure .265 exactly on the right, he'd want the left to be .265 -.002
If it were to measure .262 on the right he'd want the left to measure .262 -.002 and so on.
The functionality of the diameters has a sleeve being crimped to the diameter on the right. After crimping the parts must still slide for the full length The diameter on the left cannot grow larger than where the part was crimped or the parts will not slide the full length. If there is a transition in diameters from right to left it has to be smaller on the left.
Like I first mentioned I don't know of a scheme that would allow for this situation, nor do I think it's possible because it's not defining the nominal on the left until a quality inspection is performed on the right.
One possibility the engineer posed was using a -.002 in the geotol block and making the right side diameter a datum. I'm all but 100% certain that's not proper use.
But others may know better than I. Thank you for your continued input, I really appreciate it.
Last edited by matt.schroeder; 11-18-2013 at 06:02 PM.