Orientation question

[ImnotfromMars]

When I specify a Parallelism and/or Angularity is it necessary to specify a distance(parallelism) or an angle(angularity)?

In my case I am locating two parts to each other which will be welded in place.

In the case of the parallelism there are two surfaces which require to be parallel, but due to the complexity of the stack-up a dimension could not be given. I just want where ever they show up to be parallel.

For the Angularity there is one part with a large flat surface and a second part having several small surfaces all in the same plane at some angle from the large flat surface. I wish to specify a angularity which I understand will be a distance between two planes at an angle. The resultant angle will be different for every part produced, but all I want is the several small surfaces to be lined up with the main plane. I don't want to specify an angle.

Would someone know if this is possible?

 

[PeterStock]

It would not be necessary to have a dimension for the parallelism, but it is necessary to have the locaton of the two surfaces to be defined in some way by the drawing. For the angularity, it is necessary to define the angle, if not by an angular dimension, then by other basic dimension back to the datum or datums you are referencing.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[dgallup]

I would not use angularity if you do not care what the angle is. I think you can use profile if you are using ANSI. In an ISO environment you could use flatness with a common zone.

 

[drawoh]

ImnotfromMars,

Your geometry ought to be defined by a bunch of basic dimensions. When I do stuff like this, a few ± dimensions tend to wind up in there. You need complete definition of your geometry, somehow. If you are specifying angularity, an angle specification makes things easier for the inspector.

Parallelism is independent from distance.

Frequently, I apply parallel specifications onto sloppy ± dimensions. A ± dimension or a profile tolerance controls parallelism, but sometimes, not enough. The same goes for angularity. Often, I have a composite FCF with a sloppy profile and an accurate angle.

Just as a final note which may make things clearer, parallelism and angularity both control flatness. The faces are not allowed to extend outside the tolerance zone.

This all matters on weldments because the welders have to jig stuff. It really helps to show them what your priorities are.

JHG