Datums Defined by Targets - Can Have Modifiers?
Datums Defined by Targets - Can Have Modifiers?
It is allowed to have datum callouts specified at MMB even if datum targets are used to establish a datum. If you are trying to establish datum axis based on e.g. 2 sets of 3 datum target points you can defined them on RMB (RFS) basis or MMB (MMC) basis.
Y14.5M-1994 did not specifically offer such possibility. Paragraph 4.6.4 is only mentioning RFS option.
Y14.5-2009 introduces MMB option in paragraph 4.24.10.
Y14.5M-1994 did not specifically offer such possibility. Paragraph 4.6.4 is only mentioning RFS option.
Y14.5-2009 introduces MMB option in paragraph 4.24.10.





RE: Datums Defined by Targets - Can Have Modifiers?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Datums Defined by Targets - Can Have Modifiers?
Thanks for the clarification.
RE: Datums Defined by Targets - Can Have Modifiers?
I agree that 4.24.10 does reflect that MMB is applicable in the situation shown. In figure 4.51, we have a positional tolerance on a hole shown on a cylindrical part. MMB can be used on the datum structure and it does make sense.
We had a solid feature illustrated in 4.24.10. If we have a datum target structure on a non-feature such as shown in fig. 4-39, page 79, of the 94 standard, could we still use MMB? I don't think so.
I guess we would really have to see your drawing to positively state that MMB can be used in your situation.
Dave D.
www.qmsi.ca