Implied dimensions

[Joe Zastrow]

Is there such a thing as an implied 90 deg angles or implied perpendicularity and flatness using ASME Y14.5M-1994 standard? And can you tell me where to find info on this topic in the standard?

[cmmmike]

This is what I found for implied 90 in the ANSI Y14.5M-1982.

2.1.1.2 - Unless otherwise specified, where a general tolerance note on the drawing includes angular tolerances, it applies to features shown at specified angles and at implied 90 degree angles.

I was alway told that if the angle was not called out it was a implied 90 degree angle.

[DaddyBluto]

As I understand it (Kevin correct me if I am wrong), a true position has an implied perpendicularity in it. For example if you have a plate with one hole drilled in it and the top surface is -A-, the front is -B- and the side is -C-, then the true position of the hole called out to ABC has a perpendicularity to -A- included.

[William Johnson]

Bluto That is the way I would interpret that. It controls the form of the hole.

[kbotta]

The hole's axis is bounded by the depth of the feature. The entire feature. So yes, in a way position does control the orientation of the feature. So, the entire axis of the feature must lie inside a cylindrical (if that is what it is) tolerance zone bounded by the length of the feature. A good way to think of this is: Drop a pencil in a coffee mug (unempty of course ) And notice how the pencil (axis) lie's in the mug. FYI...0.02
Kev

[Lee Johnson]

90 degrees always unless otherwisw specified.
Flatness is another issue it is the the distance for your tolerance between two parralell planes unless othewise specified.
Note otherwise specified may be in workmanship notes on a drawing. It does not need to be on the actual drawing if it states some sort of workmanship spec. this can also apply to perpendicularity.