Use profile or symmetry to define surface feature

[Astorite]

Hi,

First post here so any advice would be appreciated as I'm primarily a mechanical analyst so rarely venture in the realms of GD&T.

However, I'm getting a test piece made to verify some simulation work and need guidance on the best way to dimension the part. I've attached a sketch showing the proposed part.

In terms of importance, the critical aspect is that the raised features in the centre are located centrally about the aperture. My DO colleague has proposed to use a combination of symmetry and parallelism to define the relationship but I think the part should be defined in term of a profile constraint. Incidentally, the values assigned aren't correct as they are only to illustrate the concept.

Many thanks

 

[MechNorth]

Didn't think you were, pmarc, but Frank had referenced him earlier in the thread, and I've seen a number of references to him in other threads recently. I've seen selective interpretations from ASME experts as well, of course; always be aware of the potential for bias and misinformation with any source.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fsincox]

I am trying to encourage people who work with the ISO's system to come and discuss issues so I can learn more from them. The resources seem scare on ISO and Henzold's book it the only current reference I have. That may be why you have seen it so much. I do not even have access to all of their standards, like I do for the ASME. I am hoping to get the new book CH has mentioned to me. I would certainly reference other books if I had them. I do have another old book, “Modern Engineering Tolerancing” by Hill and Jensen that I read many years ago, but I know it is dated. Many of you have been a good resource, too.
Frank

 

[MechNorth]

Yup. Not a criticism for using Henzold's material, Frank. Just a caveat. As you mention, there is a scarcity of decent ISO material out there, and the cost of a full set of ISO-GPS standards is prohibitive to private ownership. A few hundred dollars gets you a pretty robust set of ASME standards, but barely makes a dent in the ISO collection.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com