yang686526

asme vs. iso
does anybody have a cheat sheet on what the differences are between the two standards? doing a search for the differences give me many opportunities to attend classes to learn what the differences are. i just need a quick and dirty list of the major differences, any help would be appreciated.
scorch
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--howard aiken, ibm engineer

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big one would be "rule #1", regarding envelope principle etc.

kenat,
one of the biggest differences i found between astm-1994 and iso is concentricity and symmetry. the only similarity is the symbol that used on the drawing. this is just one of the many existing differences that has cause many issues for me, in addition to the envelope principle already stated by kenat.
according to the gd&t pocket guide (first edition) by al neumann, scott neumann copyright 1995 pg 60
"at present the iso standards do not recognize the unique interpretation of concentricity and symmetry as defined in the asme y14.5m 1994 standard. the concentricity and symmetry characteristics in iso have the same interpretations as the position characterist in the asme y14.5m 1994 standard"
if you are going to be using the iso standards, i suggest buying and reviewing the following iso standards handbooks:
also, i have never found composite profile tolerance shown, stated, or explained anywhere in the iso specifications for geometrical tolerances. i think this is a very important tolerancing tool that they are missing.
here is a good reference on the link below
major differences that exist between the two standards
seasonlee,
that was exactly what i was looking for, a good comparison of the two standards. thanks to everybody else for your responses.
scorch
don't worry about people stealing your ideas. if your ideas are any good, you'll have to ram them down people's throats.
--howard aiken, ibm engineer

well done seasonlee, i was looking for something like that to link the op to and couldn't find it.
kenat,
recently i read a book mentioned the term mmr / lmr (maximum / least material requirement), after google searching i understood it was used by iso, is it also a difference between the two systems iso and astm? expect someone who can give more detailed information about this term.
thanks for all inputs
seasonlee

mmr and lmr in iso have the same meaning as mmc and lmc in the asme y14.5m-1994 standard. there are many changes that have been made to the iso standards lately. my observation is that the iso standards are becoming very metrology based to make it easy for cmms to inspect parts. the y14.5 standard is based on design intent to assure parts will function properly.
profdon, that seems to be the general consensus about the differences from what i've seen.
kenat,
scorch,
the asme y14.5m standard is one standard that is modified once every 10 years plus or minus. under the asme standard, drawings are seen as individual legal documents.
the iso standard is not one standard...it is a group of standards...some of which seem to conflict. drawings are not seen as legal documents and are permitted to contain items such as manufacturing notes that are not allowed under the asme standard.
as for callouts, the trend is to merge the two together...for example the asme 94 picked up the iso datum feature identifier. and i've been told that the next asme release will continue that trend.
michael