control of cylindrical features with intersecting axes

[oldbob16]

I have a part with two cylindrical surfaces. The axes of the two cylinders are designed to be intersecting at an 8 degree angle, with the point of intersection dimensioned from the end of one of the cylinders. What is the correct way to control this so the axes actually intersect within a specified tolerance?

 

[pmarc]

Could you post a sketch, so that we could see the case?

 

[oldbob16]

sketch attached

 

[pmarc]

I am assuming that by saying: "Design intent is that the two axes intersect within .0003" and by showing dimension C, you want to keep one of the axes (lets say of dia. B) within .0003 cylindrical tolerance zone located and oriented to the other axis (of dia. A) and to flat inclined surface.

If that is the case, assign dia. A as datum feature A, make inclined surface as datum feature B, switch dimension C to basic, put basic angular dimension between axes A and B and apply positional feature control frame |pos|dia. .0003|A|B| or |pos|dia. .0003|B|A| (depending on function) to dia. B. Define angular relationship between datum features A & B by applying proper angularity tolerance and that will do the thing.

 

[ak762]

I would appreciate advice with similar case but more complicated cylindrical features with intersecting axes.
Will annotation be equal to position tolerance from point of GD&T according to both ASME and ISO?
Is it correct applied where design intent is mutual axes intersect within tolerance to cross holes?

 

[pmarc]

I am trying to guess why do you want to use the note instead of applying proper GD&T callouts? Is it because of difference in ASME & ISO interpretations of position tolerance or are you just afraid that a reader of your print may not understand standard symbology?

Regardless of your answer, I would say the note needs improvement - like adding diameter symbol in front of 0.1 value (just as an example), if the zones are going to be cylinders - and even with that, this will merely control relationship between each 3-step bore and corresponding dia. 30 cylinders, but will not control mutual angular relationship of bores. If we assume for a moment that the goal is to have the bores inclined at approximately 30 degrees, your note will not control this at all - there might as well be actual 40 or 50 degrees angle between bores and the note will not have any control over it.

Therefore I would strongly recommend use of symbols with the remark though that probably it will not be easy to cover both ASME & ISO interpretations of positional tolerances simultaneously. These are, by defintion, different geometrical requirements.

 

[ak762]

Because relationship for chanels are separate to each hole D30 with axes intersecting. I assumed this representation give unambiguous interpretation. Dimensioning is not completed for this sample. One of the goal to find a solution with simplicity but sufficient requirements for secure design.