gdt question on use of a word in feature control frame

[lonsgsp]

I have a drawing (drawn 1988 interpreted per MIL-STD-100)using feature control frames. The symbol used is symmetry and after the value the word "TOTAL" is used. The drawing is being redrawn to dimension & tol standards ASME Y14.5-2009. I cannot find a reference to the word being used and wondering if it was part of an older specification that is superseded by the document listed above and is no longer used.

Thanks,

Lon

 

[CheckerHater]

This is interesting.
Symmetry was discontinued in 1982 and re-introduced in 1994.
"TOTAL" was usually combined with Runout symbol (before 1982)
We need someone with several decades of experience here.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[3DDave]

It may be from one of Foster's followers. In his 1963, 1964 book on the subject (pre-ANSI) he uses the word TOTAL in his examples of symmetry. However, that is in the 'interpretation' section. But he uses the word in capital letters at twice the height (3/8" tall on the page) and in bold. I can see someone just copying what they thought they read. It also includes the use of (M) on the symmetrical features and related datum reference.

See

http://www.dtic.mil/dtic/tr/fulltext/u2/a290909.pdf

for a history before 1973. (Doesn't mention "TOTAL")

I suspect a full tolerance analysis is going to be required if there's a desire to update the drawing. A lot of concepts have not held up well and it's not always the case that what was allowed for on a drawing would actually work.

For a while I wanted to moonlight at our suppliers and have them fabricate completely useless parts that were 100% drawing compliant, but it's not an easy gig to get.

 

[Belanger]

Also -- just throwing this out there -- be sure that you are dealing with the symmetry symbol (three horizontal lines: short, long, short). Because there is an old practice of using the circular runout symbol (an arrow) supplemented with the word TOTAL as a way of indicating total runout.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[lonsgsp]

Thanks for the input and yes it is the symmetry symbol. This should give me enough information to explain should someone question why I removed it.

Lon