Critical, Major and Minor Dimensions
Critical, Major and Minor Dimensions
(OP)
Hey all,
I have a few questions about critical, major and minor dimensions and if anyone uses them in relation to mechanical parts? My work are currently reviewing their process and are seeking to implement something better so thought I would ask the experts here.
Now there is a lot of good chat on the subject - Link & Link & Link
From the above links and relevant standards, I have been able to decipher how companies usually classify critical dimensions, how they denote them on a drawing (usually the race track symbol) and how often they are inspected (usually ISO2859 or ANSI Z1.4-2003 with a relevant AQL).
However, I am yet to find anything on minor and major dimensions (i.e. how they are commonly denoted on drawings, how often they are inspected in relation to critical dimensions and if any other companies really use this). The youtube video hints at a chinese definition on major and minor dimensions but I think the approach mentioned doesn't really add any value.
I am therefore wondering the following:
- Does anyone work at a company that makes the distinction between critical, major and minor dimensions?
- If yes, how do they make this distinction on the drawing and how are critical, major and minor dimensions inspected in relation to one and other (i.e. frequency of inspection etc)?
- If yes to the first point, do they think the distinction adds value? Please bare in mind that I work in a low volume, high value manufacturing sector.
Looking forward to hearing back from you all
Euan
I have a few questions about critical, major and minor dimensions and if anyone uses them in relation to mechanical parts? My work are currently reviewing their process and are seeking to implement something better so thought I would ask the experts here.
Now there is a lot of good chat on the subject - Link & Link & Link
From the above links and relevant standards, I have been able to decipher how companies usually classify critical dimensions, how they denote them on a drawing (usually the race track symbol) and how often they are inspected (usually ISO2859 or ANSI Z1.4-2003 with a relevant AQL).
However, I am yet to find anything on minor and major dimensions (i.e. how they are commonly denoted on drawings, how often they are inspected in relation to critical dimensions and if any other companies really use this). The youtube video hints at a chinese definition on major and minor dimensions but I think the approach mentioned doesn't really add any value.
I am therefore wondering the following:
- Does anyone work at a company that makes the distinction between critical, major and minor dimensions?
- If yes, how do they make this distinction on the drawing and how are critical, major and minor dimensions inspected in relation to one and other (i.e. frequency of inspection etc)?
- If yes to the first point, do they think the distinction adds value? Please bare in mind that I work in a low volume, high value manufacturing sector.
Looking forward to hearing back from you all
Euan





RE: Critical, Major and Minor Dimensions
(Some) reasons are outlined in the enclosed document.
There were several discussions on this forum on this topic. (Example: http://www.eng-tips.com/viewthread.cfm?qid=322065)
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Critical, Major and Minor Dimensions
However, critical dimensions are broken down into categories (variable or attribute). The variable designation requires capability to be shown. The attribute designation does not require capability to be shown (i.e. a go/no-go gage could be used). This is a new system for use and there is ongoing discussion about somehow requiring some capability demonstration for attribute dimensions during PPAP to avoid excessive measuring of attribute dimensions after PPAP.
RE: Critical, Major and Minor Dimensions
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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: Critical, Major and Minor Dimensions
Critical Characteristic: Any attribute that if fails, could cause serious injury, damage, or harm.
Major Characteristic: Any attribute that if fails, could cause mission failure (or failure of the product).
Minor Characteristic: Any attribute that requires special inspection techniques.
Classification of Characteristics is called out on the drawing by numbering each characteristic within parenthesis.
(C1), (C2), etc.
(M101), (M102), etc.
(m201) or (201), (m202) or (202), etc.
The inspection level is often pre-defined, so a critical is 100% inspection, Majors have a higher percentage, and so on. But, you shall not apply a classification of characteristic onto a dimension to force inspection levels. There are other ways to force a dimension to be 100% inspected without listing it as a critical.
--Scott
www.aerornd.com
RE: Critical, Major and Minor Dimensions
http://quicksearch.dla.mil/qsDocDetails.aspx?ident...