AMontembeault
Mechanical
- May 13, 2014
- 26
I reccently had to check a drawing of a right cylinder, with a length tolerance of +/-1 and a perpendicularity requirement on each flat end of 1.5 with respect to the axis (Datum A).
I rejected the drawing, on the basis that if each end has 1.5 perpendicularity at the same time, then rule 1 is violated, as the resultant size range on the length of the cylinder based on the prependicularity tolerace would be 3, not 2, as defined by the size tolerance called out.
It was then suggested to me that I had the wrong interpretation. By having a 1.5 perpendicularity tolerance on each end, they argued that if one end of the cylinder is at 1.5, then the other end can only be 0.5 because it is regulated by the size tolerance.
So basically, the debate is my interpretation that having all 3 requirements on a drawing consititutes an "AND" requirement, where all information must agree simultaneously as presented, while the competing interpretation constitutes a conditional requirement("OR"), where the maximum deviation may only occur on one side at a given time, but either side is eligible for the maximum deviation.
(Of course the whole thing could be made a non-issue by using different combinations of GD&T, or by adjusting the tolerances accordingly, but for reasons unknown to me, there is resistance to these simple changes)
Whats the right interpretation? Can anyone link a passage in the ASME standard which clarifies this? (I do have the standard, but am not sure what phrases or keywords I should use to search).
I rejected the drawing, on the basis that if each end has 1.5 perpendicularity at the same time, then rule 1 is violated, as the resultant size range on the length of the cylinder based on the prependicularity tolerace would be 3, not 2, as defined by the size tolerance called out.
It was then suggested to me that I had the wrong interpretation. By having a 1.5 perpendicularity tolerance on each end, they argued that if one end of the cylinder is at 1.5, then the other end can only be 0.5 because it is regulated by the size tolerance.
So basically, the debate is my interpretation that having all 3 requirements on a drawing consititutes an "AND" requirement, where all information must agree simultaneously as presented, while the competing interpretation constitutes a conditional requirement("OR"), where the maximum deviation may only occur on one side at a given time, but either side is eligible for the maximum deviation.
(Of course the whole thing could be made a non-issue by using different combinations of GD&T, or by adjusting the tolerances accordingly, but for reasons unknown to me, there is resistance to these simple changes)
Whats the right interpretation? Can anyone link a passage in the ASME standard which clarifies this? (I do have the standard, but am not sure what phrases or keywords I should use to search).
