【转帖】number of decimals in a position fcf

yang686526

number of decimals in a position fcf
we are still using asme y14.5m-1982 for our commercial drawings. i have 4 position tolerences on a drawing with three place dimensions/tolerences.  when using a feature control frame on a inch dimension, does the number of decimals in the f.c.f have to be the same number as in the dimension/tolerance it is attached to?
annex a of 1994 std lists principle changes & improvements
a4 says "the number of decimal places to be used in a dimension and asociated tolerances for unilateral, bilateral, basic, or limit dimensioning is presented for both metric or inch applications."
so it doesn't explicitly list any change on the issue of number of decimals in dimension & tolerance matching.
1994 says that yes they have to match.
so, i'd guess that at 1982 they have to match.
kenat, probably the least qualified checker you'll ever meet...
totalboob,
according to the 1982 version which i just did look at, the examples do not bear out the necessity for the same number of decimal places in both.  this is not necessarily born out by the text.  i did not go beyond the examples.
a star for kenat.  not enough of those going around these days.   anyway, that was a very good explanation.  i didn't know anyone still had old copies of 1982 floating around.
matt lorono
cad engineer/ecn analyst
silicon valley, ca
after reading over the standard countless times, i think i have found my own answer.  the number of places in the fcf sould match the basic dimension it is associated with, not necessarily the dimension it is under.  please tell me if i am wrong, again.
that has been my interpretation of it, but i am willing to accept another if it can be pointed out in the standards.
believe it if you need it or leave it if you dare.fff"> - robert hunter

i used the 1982 version all the way through to 1997, and still have my beatup copy. we always matched the inch decimal places in the fcf with the associated dimension. the examples, being metric, weren't much help, but gdt trainers i knew who had access to asme committee members told us that was the intention since the inch samples matched zeros and didn't drop them. ref. paragraph 2.3.2.
it seems to me that it was shown that way in lowell foster's "geometrics ii & iii" books, but i don't have one available now to check it out.