Three holes on same plane

[Sa-Ro]

Dear All

Our requirement:

1) Hole A1 and A2 shall be on same plane within variation of dia 0.05.

2) Hole A1 and A2 shall be symmetrical to hole B within variation of 0.05 along X axis.

3) Hole A1 and A2 shall be coincide with a plane passing thru hole B center axis within variation of 0.05 along Y axis.

4) Outer size 91 and 38 shall be aligned as shown in drawing.

5) Hole D1, D2, D3 and D4 shall be symmetrical to hole B within variation of dia 0.05

6) Hole C1 and C2 shall be on same plane within variation of dia 0.05.

7) Hole C1 and C2 shall be symmetrical to hole B within variation of 0.05 along X axis.

8) Hole C1 and C2 shall be coincide with a plane passing thru hole B center axis within variation of 0.05 along Y axis.

Kindly suggest us, how to define our requirement as per ASME Y14.5:2018 GD&T standard.

Thank you.

 

[Wuzhee]

My bad. I wasn't familiar with VC so I looked into the standard. It's not even fully explained and represented (maybe just for me). Looks kinda strange and confusing to me. Just as AME/UAME. But that's offtopic here.
[sub](also I hate that the standard uses min/max dimensions on their figures. Why can't they stick to regular +- or limits/fits?)[/sub]

 

[Burunduk]

Wuzhee,
Virtual condition is what you have to consider when analyzing the worst case for features of size fitting together. It's a bounadry smaller than the minimum hole size or larger than the maximum shaft size generated by the MMC and the largest possible location/orientation deviation.

 

[Wuzhee]

It was the wording which got me, as I never really called it it's standardized name. But thanks for explaining. I haven't realized I did stuff with VC before
O

 

[Burunduk]

Wuzhee,
ASME Y14.5 terminology-wise, it is Virtual Condition when the geometric tolerance which is added or reduced from the MMC/LMC size is applied with the MMC/LMC modifier. If the geometric tolerance is applied RFS, then the boundary is simply called the Inner Boundary (IB) or Outer Boundary (OB). Also, as you may know If the only thing that affects the assembly ability is the sizes of the internal and external features, such as when a single shaft is assembled into a single hole manually without any restrictions, only the MMC sizes are compared and none such boundaries (VC, IB or OB) are considered.

 

[Sa-Ro]

Never. Capital letters are for holes, lowercase for shafts.
Look into iso 286-2.

Thank you very much.

 

[Burunduk]

Or ANSI B4.2 - Preferred Metric Limits and Fits.

 

[Sa-Ro]

Thank you Burunduk