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ISO 8062 and ISO 2768 for one dimension

M

MaciejM

Automotive
Joined
May 21, 2025
Messages
3
Hi everyone,

I have a drawing of a cast plate, and on this drawings there is a dimension for both cast and machined features. I want measure this 53,9 distance from a cast hole to a machined face. Should I add tolerances CT9 (±1) from ISO 8062 and from ISO 2768mK (±0,3), or just stick to CT9?
 

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What is CT9? Is it a tolerance grade? Your machined surface seems too small to locate the hole, or vice versa.
 
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Why do you want to use any of these redundant standards?
Just apply the tolerances that will make it work.
What are the functional considerations?
Does the flat surface locate the part in the vertical direction or the hole? The one that does should be a datum feature of some order, probably not the primary bacause they both are too small to orient the part. Choose a datum reference frame that makes sense for constraining all relevant degrees of freedom. The distance dimension should be basic. Then if the hole is controlled from the flat end use position, or if the flat end is controlled from the hole use profile. Maybe they both should be dimensioned and controlled relative to something else and then none of them is a datum feature. Their distance from each other would result from both their location tolerances. Assign the tolerance values as wide as your design can tolerate. Good luck, and get rid of those silly general +/- standards.
 
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Burunduk said:
Why do you want to use any of these redundant standards?
Just apply the tolerances that will make it work.
What are the functional considerations?
Does the flat surface locate the part in the vertical direction or the hole? The one that does should be a datum feature of some order, probably not the primary bacause they both are too small to orient the part. Choose a datum reference frame that makes sense for constraining all relevant degrees of freedom. The distance dimension should be basic. Then if the hole is controlled from the flat end use position, or if the flat end is controlled from the hole use profile. Maybe they both should be dimensioned and controlled relative to something else and then none of them is a datum feature. Their distance from each other would result from both their location tolerances. Assign the tolerance values as wide as your design can tolerate. Good luck, and get rid of those silly general +/- standards.
Click to expand...
Both standards specifies general tolerances for linear dimensions, when they are not explicitly stated on technical drawings. As you see there is no tolerance on 53,9 dimension. So in that case we have to take this tolerance from one of those two norms. But:
- it is a cast part, and it's define as ISO8062 CT9 so for 53,9±1
- it is a cast part where one surfece is milled, and I'm not covinced whether I can use ISO8062 norm because for this purpose we have ISO2768 standard (in this case on drawing is ISO2768mK).
That is why I try to find someone with experience in cast part. This is not my drawing, I need measure it but I don't know what tolerance should I use.
 
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Just measure it and leave the "Accept/Reject" and tolerance entries blank, or use both tolerances on the inspection report and put on separate Accept/Reject choices for both of them. If they are both "Accept" or both "Reject" it won't matter which applies. If one is "Accept" and the other "Reject" then call the customer and tell them that the part will be put on a shelf until that is clarified.
 
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MaciejM said:
Both standards specifies general tolerances for linear dimensions, when they are not explicitly stated on technical drawings. As you see there is no tolerance on 53,9 dimension. So in that case we have to take this tolerance from one of those two norms. But:
- it is a cast part, and it's define as ISO8062 CT9 so for 53,9±1
- it is a cast part where one surfece is milled, and I'm not covinced whether I can use ISO8062 norm because for this purpose we have ISO2768 standard (in this case on drawing is ISO2768mK).
That is why I try to find someone with experience in cast part. This is not my drawing, I need measure it but I don't know what tolerance should I use.
Click to expand...
Ok, now that clarifies the intent of the question. I think 3DDave offered a solution that makes perfect sense starting from his second sentence.
 
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3DDave said:
Just measure it and leave the "Accept/Reject" and tolerance entries blank, or use both tolerances on the inspection report and put on separate Accept/Reject choices for both of them. If they are both "Accept" or both "Reject" it won't matter which applies. If one is "Accept" and the other "Reject" then call the customer and tell them that the part will be put on a shelf until that is clarified.
Click to expand...
This element is a part of the PPAP, I need to measure it to be sure that our supplier would deliver a decent product. If I don't know what tolerances should be in some dimensions, how can I tell our quality department that it is ok or not? I can reject the part if it's out of tolerance...
 
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That's a question for your engineers to resolve. Passing the decision to you isn't fair. It also complicates things when one has to grab a book to find out what the tolerances are. Just copy and paste the applicable ones to each pertinent dimension. As far as I know, the values in those standards are ones that typical production will make if you don't tell them anything. The values are selected so that most product will be accepted, regardless of the part function.

Someone should have done a tolerance analysis to determine how much of and what kind of variation acceptance will still result in a usable product.
 
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Send back to the engineer who let out an incomplete part definition for PPAP to solve their problem.
 
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The PPAP should have steps for document and process reviews.

"Engineering drawing lacks tolerances, thus the part cannot be inspected."
 
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