ISO translation

[Andera]

Two questions for the ISO-ASME experts:
1. Is DV -variable distance (ISO symbol) same as translation modifier (triangle) ASME's modifying symbol? If not, what would be the subtle differences?

2. Does CF - contacting feature (ISO symbol) have the same meaning as:
BSC "BASIC" (Y14.5)
or same meaning as movable datum target ASME symbol
or neither one?

 

[greenimi]

ISO experts: please correct my statements below:


1.) Looks like thy are the same. Subtle differences??? No idea.
2.) CF (ISO) = BSC (ASME). Subtle differences??? No idea.

Anyone else....

 

[pmarc]

1. The meaning of [DV] in ISO is indeed similar to ASME's translation modifier, however according to ISO 5459:2011, Datums and Datum Systems, its primary use is to unlock the default basic location constraint between associated features used to establish a common datum, e.g. datum axis A-B established from two nominally coaxial cylinders A and B. There is, however, no need to apply this modifier in case of location constraint between primary and secondary or secondary and tertiary associated features, because by default in ISO they are constrained in orientation only.

2. [CF] in ISO and BSC in ASME have totally different meanings. Again per ISO 5459:2011, CF is used in conjuction with datum targets when the intent is to define that an associated feature used to establish a datum is not of the same type as the nominal feature. This tool does not exist in Y14.5.

 

[Andera]

Thanks pmarc.
Regarding [DV] should I understand that restriction to use it in the same time with MMR is also present?
Never seen [DV] M -circle- but for my functional gaging concepts could be even feasible?

 

[pmarc]

Andera,
Let me repeat. The [DV] modifier is intended for usage when there is no requirement to keep basic location between associated features used to establish a common datum.

Establishing a common datum by two MMVC boundaries constrained in orientation only sounds like quite troublesome datum definition.