Tolerancing on a Max dimension 1

[Mike_1968]

Hello all:

I'm new to the forum and have a question that I hope can get answered. We have a customer that calls out 4 mm Max on a clip opening. The opening sometimes close after processing because the material is spring steel. The same customer does not want closed clips and sent this explanation to us. It doesn't make sense to me.

All,

See attached part print and the areas I have highlighted with a red box. There is a note that specifies that any untoleranced dimension has a tolerance of +/- 0.8mm. Since the gap in the clip has a specification of 4mm MAX, this implies that the upper limit of the tolerance is 4mm, therefore the minimum spec would be 2.4mm (4.0 – (2 * 0.8)).

Or in other words, the actual tolerance range is:

2.4 – (-0.8) – (midpoint) – (+0.8) – 4.0

because 4.0 is defined as a maximum allowable spec.

Thank you all for your input.

 

[chez311]

Mike,

What standard does your print conform to? In Y14.5-2009 the term "MAX" has special meaning and typically means that the dimension can vary from 0 to the specified "MAX" value unless there is a minimum limited by some other feature/constraint. See section 2.5 of the standard - I don't believe that once "MAX" is called out it is any longer considered an untoleranced dimension. I would avoid the use of MIN/MAX especially if it is an important feature and have the customer change their print - it can cause a lot of confusion in its interpretation as you can see, they should have supplied a tolerance band that is acceptable instead of just a max dimension.

 

[ewh]

I agree with chez311... MAX and MIN dimensions are considered absolute limits (per Y14.5) with no other applicable tolerance.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[dgallup]

Me three. Putting max on a dimension means it could go to zero and still be OK. There is no lower limit. They need to change their drawing if they need a minimum value and then you can requote because you are either going to need some kind of control or scrap non-conforming product.

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