Can you use Projection on Angularity?

[randy64]

We want to control the angle of a hole, but position is not that critical. I realize that if we used True Position with Projection, it would accomplish what we want, but am curious if we can use just angularity and then project it. This may also apply to situations where we have a surface that we want to control with angularity, but also project that tolerance beyond the surface itself.

I don't see any examples of this in the standard (we are using ASME Y14.5M 1994). Any sources that you can provide are appreciated.

Thanks!

 

[Burunduk]

Yes, you can use the projected tolerance zone modifier with an orientation tolerance for a hole, including angularity, which is one of the orientation geometric characteristics.

In ASME Y14.5M-1994 see para. 3.4.7, page 48:

"Feature Control Frame With a Projected Tolerance Zone. Where a positional or an orientation tolerance is specified as a projected tolerance zone, the projected tolerance zone symbol is placed in the feature control frame, along with the dimension indicating the minimum height of the tolerance zone."

Don't use it for angularity applied to a surface. It makes no sense.

 

[randy64]

Burunduk, thank you!

I would argue that using projection on a surface could make sense. Consider the following: I have a block with an angled surface. A plate is attached to this block and projects out 4 inches from that block. I could use Angularity to control the angle of the block surface and add Projection as a way to control where the plate ends up 4 inches out from the block surface. I realize there are probably better or more efficient ways to do this - I'm just making an academic argument for the use of Projection of an Angularity callout on a surface.

Again, thanks for helping.

 

[Burunduk]

Randy,
When a projected tolerance is applied to a press fit or threaded hole, the extension of the hole axis is controlled within the projected tolerance zone. The hole itself is imperfect, but its axis is a straight line, that's why you are able to extend it unambiguously.
If you apply the projection symbol to a tolerance specifying a requirement for a surface, what will be extended towards the projected tolerance zone? A tangent plane? There is no such specification. A better way would be to determine the tolerance you should apply to the surface itself, so that a plate that assembles to it is limited adequately. A simple CAD simulation or a trigonometry calculation would do.