GD&T Call out

[cmmmike]

Hi all

I need to know what a GD&T call means


0.14m/A/Bm/Cm
0.10m

There is one true position symbol in a box in front of the 2 feature control frames. The true posion note checkes 3 bushing locations. Does the bottom note mean the 3 bushings to each other? Or is it a best fit? I am running 3.5 mr2.


Thanks for the help

[Duckhunter]

GD&T

You will want to do a best fit to the 3 bushings, the dimension the TP of the bushings

Tim

[Ron OLoane]

Yes, it is a best fit when there are no datum callouts. So take the three holes, best fit them, zero one of them, and evaluate the position of each.

[BSchwark]

Where datum references are not specified in the lower segment of the feature frame it is free to be located and oriented within the boundries established and goverened by the upper feature control frame. I believe this is perpendicularity and orietation as a group of your 3 bushings. Review ASME Y14.5M 1994.

BS

[cmmmike]

I hope this not a dumb question but. I dimension them for the top true position note in X & Z do I due the same for the bottom note. One more question, Do I use 3d or the 2d for my options.

Thanks for the help.

[Duckhunter]

question2

You would dimension them in the same manner that you had in the fisrt part of the FCF. 2ndly, you would want to use a 2 dimensional rotate.

Tim

[Paul Sarrach]

The only dumb question, is the one that is not asked.

Unless it is a 3d feature always true position in 2d.

I always like to stay in the correct working plane when writing a program or tolerancing, it will save you headaches later.

[cmmmike]

Thanks for the help.