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# ISO GD&T Paralellity control on multiple features

## ISO GD&T Paralellity control on multiple features

(OP)
Hi, I have a question regarding how to use the paralellity control on multiple features in a section view (see attached picture).

I want the top of each ridge to be within the same tolerance planes. The way it is illustrated on the attached drawing is how i think it should be, but i am very unsure about it. Could someone please tell me this is correct, or tell me how it should be?

### RE: ISO GD&T Paralellity control on multiple features

Jorgen Fone Pedersen,

As noted in your other post, you need to take a course in GD&T.

I am fairly certain that ISO does not allow you to specify a centre-line as a datum. Your datums must be attached to features you can attach fixtures to. Do you want parallelism or position? I have no idea of what you are trying to do.

--
JHG

### RE: ISO GD&T Paralellity control on multiple features

First of all you made the datum a center plane and we don't know of what feature it is the center. Far better to make some flat surface the datum so it can be used to level the part for measurement. Usually one picks a feature that will actually be locating the part the way it will be used in practice. Then do you only want each ridge to be parallel to A within it's own tolerance zone or do you want both ridges on one side to be within a common tolerance zone?

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

### RE: ISO GD&T Paralellity control on multiple features

(OP)
drawoh: I live in norway and these kind of courses are not exactly readily available, and all online courses i have found only apply to ASME Y14.5. And i want parallellism as stated earlier.

I agree the that it is more logical to use a flat surface as the datum, using the surface between the ridges is possible i suppose. I want both ridges on one side to be within a commom tolerance zone all over the surface of the entire feature. It is the height of each ridge according to eachother that is critical in this application

### RE: ISO GD&T Paralellity control on multiple features

Jorgen Fone Pedersen,

That may make the case for the ASME standard. More literature means it is easier to learn. The actual ASME standard is something around $100US. I understand that getting all the ISO literature in-house is way more expensive. -- JHG ### RE: ISO GD&T Paralellity control on multiple features I have to believe these courses are available in Norway if you know where to look. In the US these are usually taught at technical colleges or "junior" collages where people go to learn trade skills or do preparatory work before going to a university. The cost is usually fairly reasonable. There have to be many design and manufacturing companies in Norway that need trained designers and draftsmen. Do you work for a company? If so then there must be someone senior to you who is knowledgeable, ask them how they learned. ---------------------------------------- The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows. ### RE: ISO GD&T Paralellity control on multiple features #### Quote (drawoh) The actual ASME standard is something around$100US

You are living in the past: https://www.asme.org/products/codes-standards/y145...

@ Jorgen Fone Pedersen:

Several basic concepts are explained very thoroughly

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

### RE: ISO GD&T Paralellity control on multiple features

JFP:

Regarding training...My first exposure to GD&T was with ASME Y14.5 in 1983 (it was sanction by ANSI back then) and not ISO GPS. Since around the year 2000 I have attempted to understand ISO GPS, but with great difficulty for the same reasons you state - lots of different standards, high cost and lack of classes in the USA. It appears to me that with the ISO GPS system, you must study and comprehend many standards to gather a complete understanding of the concepts, and then figure out how to put the whole "system" together. As a contrast, the ASME 14.5-2009 standard attempts to organize all of related concepts in one document. In my opinion this makes Y14.5 a better place to start to get the basics concepts - that apply to ASME and ISO alike - under your belt. Others may disagree.

The geometry of engineered parts is the same the world over. They have characteristics of size, form, orientation and location. All the ASME an ISO GPS standards do is provided conventions and symbols to communicate these characteristics. Differences in how this is accomplished are where the confusion exists. Remember too the application (selection) of the symbols is much harder than interpretation of them.

Certified Sr. GD&T Professional

### RE: ISO GD&T Paralellity control on multiple features

CheckerHater,

Ouch! I could have sworn I paid something around \$120 for ASME Y14.5-2009.

--
JHG

### RE: ISO GD&T Paralellity control on multiple features

#### Quote (mkcski)

Remember too the application (selection) of the symbols is much harder than interpretation of them.

Yep. I agree with this. And since it's a language (a symbolistic one) we can say the same thing with different "words" / "symbols" and from here to reach the disagreement point is just a small step.....

### RE: ISO GD&T Paralellity control on multiple features

@ drawoh:
So did I! Time sure flies fast

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

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