Matt the situation is this:
1. a surface is located with a toleranced dimension.
2. that surface is 90 deg from a different surface.
3. no angle dimension exists.
4. no default tolerances are called out in the title block or in general notes.
According to section 1.4 Fundamental Rules:
"(i) A 90" angle applies where center lines and
lines depicting features are shown on a drawing at
right angles and no angle is specified. See para.
2.1.1.2.
(j) A 90" basic angle applies where center lines
of features in a pattern or surfaces shown at right
angles on the drawing are located or defined by basic
dimensions and no angle is specified."
Paragraph 2.1.1.2 "Implied 90" Angle. By convention,
where center lines and surfaces of features of a part
are depicted on engineering drawings intersecting at
right angles, a 90" angle is not specified. Implied 90"
angles are understood to apply. The tolerance on
these implied 90" angles is the same as for all other
angular features shown on the field of the drawing
governed by general angular tolerance notes or general
tolerance block values. Where center lines and
surfaces of a part are depicted on engineering drawings
intersecting at right angles and basic dimensions
or geometric controls have been specified, implied
90" basic angles are understood to apply. The tolerance
on the feature associated with these implied 90"
basic angles is provided by feature control frames
by a basic size and tolerance symbol as in Fig. 2-
3. See ANSI B4.2 for complete information on this
system."
As there is not default tolerance given in the title block or in notes, there is no tolerance. A .99-1.01 x 2.99-3.01 block is only required to fit within the tolerances as a parallelogram, not a rectangle. Without an angular tolerance the angle of the parallelogram can be anything including 45 deg or bigger.
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
