Y14.5 Feature Modifier Default
Y14.5 Feature Modifier Default
(OP)
At the risk of answering my own question, I am looking for some reassurance that I am making the correct interpretation of the standard.
For tolerance of position, beginning with the 1982 revision of ANSI Y14.5M, it is my understanding that in the absence of a material condition modifier in the feature control frame, the default is S (RFS). Prior to 1982 I believe this default was M (MMC). Is it safe then to assume that drawings released prior to 1982 will default to MMC and later drawings will default to RFS in the absence of a modifier? This seems kind of risky.
Thank you,
smr
For tolerance of position, beginning with the 1982 revision of ANSI Y14.5M, it is my understanding that in the absence of a material condition modifier in the feature control frame, the default is S (RFS). Prior to 1982 I believe this default was M (MMC). Is it safe then to assume that drawings released prior to 1982 will default to MMC and later drawings will default to RFS in the absence of a modifier? This seems kind of risky.
Thank you,
smr





RE: Y14.5 Feature Modifier Default
In cases like this, you probably have to interpret the drawing as a functional requirement and determine whether it would be better to be MMC or RFS.
--Scott
For some pleasure reading, the Round Table recommends FAQ731-376
RE: Y14.5 Feature Modifier Default
The basic rules for implying a material condition modifer have been covered over the years by what were initially defined as "general rules 2 and 3" in earlier versions of the standard.
"Rule 3" covered all geometric tolerances (with the exception of positional tolerance) and defined that RFS is assumed to apply where no material condition modifier is shown in the feature control frame. This applies to both applicable tolerances and/or datum references. This has been a consistent interpretation for all versions of the standard to date.
"Rule 2" applies only to positional tolerances and defines differing interpretations depending on the Y14.5 standard year of issue. The general interpretation rules for positional tolerance apply as follows:
ANSI Y14.5-1973
For positional tolerances only, MMC is assumed to apply where no material condition modifier is shown in the feature control frame. This applies to both applicable tolerances and/or datum references.
ANSI Y14.5M-1982
For positional tolerances only, no implied material condition exists where the material condition modifier is omitted in the feature control frame. MMC, LMC or RFS must be specified for the tolerance and/or all applicable datum features. Omission of the appropriate modifiers constitutes an incomplete specification.
ASME Y14.5-1994
For all geometric tolerances (including positional tolerances), RFS is assumed to apply where no material condition modifier is shown in the feature control frame. This applies to both applicable tolerances and/or datum references.
GDT_GUY
RE: Y14.5 Feature Modifier Default
RE: Y14.5 Feature Modifier Default