Effective Training Inc. Message Board

Good morning, Can you tell me if it's permited to use true position composite tolerances for features of different sizes or only on features that are truely identical? I have a round plate with 3 half circle cutouts spaced 120 degrees apart but the diameters are all different but I would like to keep the pattern tighter than the features to the outside shape. right now I'm using a composite position tolerance but I'm wondering if I should be using profile of a surface and find some other way to relate the pattern.

Thanks,
Len

Hi Craig,

I will need more information to accurately answer your questions. What is datum A? What is datum B? You can e-mail your drawing to me and a brief description of its function so I can get the full picture. Some things to keep in mind about composite position tolerancing.
1. Composite position tolerancing applies to feature of size patterns only. This means the the 3 features that you are tolerancing must be dimension as a pattern. The drawing show that you have the three toleranced seperately with seperate position tolerances applied.
2. The upper segment of the composite position tolerance frame controls the location of the pattern.
3. The lower segment of the composite position tolerance frame controls the relationship between the features within the pattern and their orientation to the datums only. Not location.
Without knowing what the which feature are the datums and the function of the part, it looks like the three notches are good candidates for profile tolerancing.

Send me your drawing and I will be able to give you a more detailed answer.

_________________
Best Regards,
Roy Cross
ASME GDTP Senior Level S-0488
Dimensional Engineering Mentor
Effective Training, Inc.
2118 S. Wayne Rd.
Westland, MI. 48186
royc@etinews.com
http://www.etinews.com

Hi Craig

First ofall Using the Position symbol for the Three Features in 120Deg is not Good.

You can have Profile Tolerance The PLTZF and FRTZF will be applicable for Profile of surface also.

and No matter what the size of feature is you can have SIM REQT for those things

Hope you are cleared

JANA
Mahindra and Mahindra Ltd
INDIA

Technically, these are not features of size by definition, so a positional callout is not applicable here.