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Revision Letters on Drawings

Revision Letters on Drawings

Revision Letters on Drawings

(OP)
What is the appropriate method for calling out a revision in the field of a drawing?  I have always understood the symbol is a circle with the revision letter in it, with no leader of any kind.  I have also understood that the revision symbol must be placed as close to the revision as possible.  Two questions arise?

1) Can a revision symbol be shown on the surface of a part, if that is the only way to place it close to the particular revised area?

2) Can a leader with an arrow be used to identify the revision, if the symbol cannot be placed close to the revised area?

Thanks,
Jeff

RE: Revision Letters on Drawings

jmarkus,

If it is a revision some change must have been made to the drawing whether it be a dimension or a note.  The easiest method is to place the modification symbol (I have previously seen it as an inverted triangle with a letter in it)next to the dimension or note that has changed.  

If the changes are significant and it is more difficult to put a mark on the drawing itself the changes should be described in the modifications box of the drawing.

Only my thoughts

gjb

RE: Revision Letters on Drawings

The proper revision symbol, as I understand it, is a triangle containing a letter or letters, such as AA, or numbers if desired.  The triangle, usually refered to as a "Carat", is placed, if possible, below the dimension or note which has been changed, and pointing at the dimension.  It must, always, read in the same direction as the dimension or note to which it refers.

Drawings usually contain a "revision block", often located in the upper right hand corner of the title block.  It should have a collumn for the revision designation, a brief discription of the item changed, the date the drawing was revised, and the person making the drawing revision.  Some, also, need an approval collumn.

Hope this helps.

RE: Revision Letters on Drawings

(OP)
Our drawings only contain enough information for GD&T.  We rely on the math data (CAD) for the basic geometry of the part.  Because of this, it is possible for geometry which is not dimensioned or toleranced (well, it is toleranced, but covered by the general tolerance note on the drawing) to be modified.  But there would not be any associated note or dimension to describe this change, just the visualization of it on the drawing.

So now what?

Thanks,
Jeff

RE: Revision Letters on Drawings

ASME Y14.35-1997, Revision of Engineering Drawings and Associated Documents" states the following for identifying revisions on the field of the drawing:

5.4 Revision Symbol
The revision symbol may be used to identify an item or area of change on the drawing. The symbol should be placed at or near the location affected by the change.  Where many individual changes required by the revision authorization document would create an overly crowded condition, a single revision symbol may be used. See Fig. 5 sketch (d).

5.4.1 Symbol Application.
When a revision symbol is used, the revision letter, and the sequence number when used, shall be enclosed in a circle to form a revision symbol. See Fig. 5 sketch (a). A leader(s) may be added to the circle to indicate a specific location. See Fig. 5 sketches (b), (c), and (d).


GDTGUY

RE: Revision Letters on Drawings

(OP)
Thanks GDTGUY.  That answers my question 2, about the leader.  But I still wonder if it is acceptable or not to show the revision symbol on the part itself (as opposed to a region outside it).

Jeff

RE: Revision Letters on Drawings

Manufacturing engineering may have different conventions as indicated in the ASME standard.

The most common practice in construction is to draw a cloud around the content that has changed (just a bunch of arcs) trying to minimize enclosing stuff that hasn't changed; then draw a revision delta (a triangle) touching the cloud; then put the revision identifier in the delta (either a letter or a number depending on your organization's practice); and finally put the revision identifer, date, and description of the revision in the drawing revision block.

Paul

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