Tp Drf

[Bob Pierce]

When working with sheet metal and dimensioning true position of punched holes, from a design stand point is it necessary to include in the FCF the datum that lays in the same work plane as the feature being dimensioned ?

[Matthew D. Hoedeman]

Generally it is included, but I think that is simply to SHOW that you are to dimension it with all degrees of freedom constrained. Almost all the prints I get will include ABC in the FCF for sheet metal pierce holes.

On a side note, you MAY want to TP them in the report with PERP TO CENTERLINE turned on to simulate a stab-pin check (it will 'remove' the surface variation from the TP dimension).

[Bob Pierce]

I was wondering because I have FCFs with TP of similar features to lAlBlCl and also just lAlBl having the same work plane and on the same print.

[Jan d.]

Are you using the XactMeasure GD&T? It can do a simultaneous evaluation, which is what you have to do for similar DRF's, unless otherwise specified, see the standard.

Take all the AB FCF's and evaluate them simultaneously (you can find this under the Insert/Dimesions menu), same with the ABC frames. I do this all the time and it works good for me. Works great.

Also, from version 4.1 and higher, MMC on datums is handled correctly. In 4.0, there were some minor issues, but in 4.2 they have all been corrected.


Jan.