Eurotex
Mechanical
- Sep 14, 2020
- 11
Recent convert to ISO GPS, so I want to make sure I'm thinking correctly about things now that size does not control form (no rule 1!) and I also need to rely on form tolerances much more than with ASME. I'll likely still use some ASME terminology.
For the sake of discussion, let's consider an external diameter with a size callout of 7.0 ±0.1 (LP), where "LP" means local 2-point size.
Now let's think of different ways that this feature could be controlled and describe the implications for the Maximum Material Boundary (MMB). I'll neglect profile controls for now.
If the feature is related to a datum reference frame, I think the smallest of the following controls would determine the MMB.
MMB = 7.1 + position if (LP) was replaced by (E)
MMB = 7.1 + circularity + position
MMB = 7.1 + cylindricity + position
MMB = 7.1 + circular runout
MMB = 7.1 + total runout
And if circularity was omitted from the second specification, I believe this would leave the MMB unspecified, in that case.
If the feature is not related to a datum reference frame, I think the smallest of the following controls would determine the MMB.
MMB = 7.1 if (LP) was replaced by (E)
MMB = 7.1 + cylindricity
MMB = 7.1 + circularity + axis straightness
MMB = 7.1 + circularity + surface straightness
Please let me know if you agree or disagree. Also let us know if you can think of any other cases. I tried to list all scenarios except for the use of profile.
For the sake of discussion, let's consider an external diameter with a size callout of 7.0 ±0.1 (LP), where "LP" means local 2-point size.
Now let's think of different ways that this feature could be controlled and describe the implications for the Maximum Material Boundary (MMB). I'll neglect profile controls for now.
If the feature is related to a datum reference frame, I think the smallest of the following controls would determine the MMB.
MMB = 7.1 + position if (LP) was replaced by (E)
MMB = 7.1 + circularity + position
MMB = 7.1 + cylindricity + position
MMB = 7.1 + circular runout
MMB = 7.1 + total runout
And if circularity was omitted from the second specification, I believe this would leave the MMB unspecified, in that case.
If the feature is not related to a datum reference frame, I think the smallest of the following controls would determine the MMB.
MMB = 7.1 if (LP) was replaced by (E)
MMB = 7.1 + cylindricity
MMB = 7.1 + circularity + axis straightness
MMB = 7.1 + circularity + surface straightness
Please let me know if you agree or disagree. Also let us know if you can think of any other cases. I tried to list all scenarios except for the use of profile.
