General notes and flag notes

What they say. General notes carry what a picture and its dimensions cannot: the standard the drawing is read by, the material when it is not in the title block, the finish, edge breaks, heat treatment, marking, inspection and the papers to deliver with the parts.

Where they are. ASME Y14.100 has them under the heading NOTES on sheet 1, or has sheet 1 say where they are, and has them numbered so a note can be cited: SEE NOTE 4, in a title block box or beside a feature.

What they apply to. The whole drawing, unless a note limits itself, as in ALL MACHINED SURFACES, or is a flag note, which applies only where its flag appears.

Local notes are the other kind: short notes placed at a feature with a leader, such as 4X ⌀.250 THRU or BREAK EDGE, which apply to that feature only.

Why it is there. ASME Y14.5 requires every dimension to have a tolerance, except one marked as reference, maximum, minimum or stock. Most dimensions get theirs from the defaults, so a drawing need not repeat ±.005 on every number.

Under it, a drawing commonly states:

• The general tolerances, by decimal places and for fractions and angles, in the title block's tolerance block, or by a class such as ISO 2768-m on an ISO drawing.
• The units of every dimension.
• Other defaults: edge breaks, fillet and corner radii, surface roughness.

Otherwise specified means anywhere the drawing says something for a particular feature: a tolerance written on the dimension, a local note, a flag note, or a note that limits itself to a kind of feature. There, the drawing's own statement applies and the default does not. The values of the defaults are each company's choice, not the standard's, so read them off every drawing.

1. At the feature. A tolerance on the dimension, or a local note with a leader, applies to that feature, whatever the defaults say.
2. At the flags. A flag note applies at its flags, and where it speaks to the same thing as a general note, it is the more particular of the two.
3. For a kind of feature. A general note that limits itself, such as ALL HOLES or ALL MACHINED SURFACES, applies to those features over the drawing-wide default.
4. Everywhere else. The general notes and the title block's defaults.

When they truly disagree, say a general note gives one finish and the title block another, the drawing contradicts itself. Nothing makes one silently win, so ask whoever owns the drawing before parts are made.

A note that cites a specification, such as PER MIL-PRF-8625, brings that specification's requirements onto the drawing, with the type and class the note chooses.