I am learning tolerance stackups and I am using Alex Kurlikovski book (Fundamentals of Geometric dimensioning and Tolerancing, 2nd edition). I have a question about the stackup tolerance calculation --fig 9-14 page 265—attached—
Minimum distance X min calculation shown is 4.5mm. Someone around here, who has way more experience than me in those kind of calculations, is claiming that the “real” X min calculation should be 4.1 (not 4.5 shown) because the form error was not included.
In the book: X min is :
69.6 (min length) – 50 (basic) - 10(basic) – 8.6/2 (max size for the hole) - (0.6+1)/2 (hole at the LMC, hole position is at MMC) = 4.5mm
Our expert is claiming the calculation should have started from 69.6 - 0.4 = 69.2 and not from 69.6. Therefore, the result would be 4.1mm and not 4.5mm.
Justification: the size of the feature (length) still has to be ±0.4mm (70.4/69.6 = 70±0.4), if the opposing points meet the size specification and the envelope meet rule#1, then the length meet the requirements. The form error was not taking in consideration for the calculation in the book. (a gage can use all 0.4mm in form error and still be making contact with the datum feature simulator)
I know pmarc had some issues with X min calculation in fig 9-12 page 263 (x min should be 2.7 and not 2.9) and here is that specific thread.
And it’s exactly as pmarc stated: “It is weird to disagree with such authority”
Now, going back to our issue (page 265): Ii is our “expert” points us in a right direction or “the unclaimed form error” is not applicable here?
Thank you
Minimum distance X min calculation shown is 4.5mm. Someone around here, who has way more experience than me in those kind of calculations, is claiming that the “real” X min calculation should be 4.1 (not 4.5 shown) because the form error was not included.
In the book: X min is :
69.6 (min length) – 50 (basic) - 10(basic) – 8.6/2 (max size for the hole) - (0.6+1)/2 (hole at the LMC, hole position is at MMC) = 4.5mm
Our expert is claiming the calculation should have started from 69.6 - 0.4 = 69.2 and not from 69.6. Therefore, the result would be 4.1mm and not 4.5mm.
Justification: the size of the feature (length) still has to be ±0.4mm (70.4/69.6 = 70±0.4), if the opposing points meet the size specification and the envelope meet rule#1, then the length meet the requirements. The form error was not taking in consideration for the calculation in the book. (a gage can use all 0.4mm in form error and still be making contact with the datum feature simulator)
I know pmarc had some issues with X min calculation in fig 9-12 page 263 (x min should be 2.7 and not 2.9) and here is that specific thread.
And it’s exactly as pmarc stated: “It is weird to disagree with such authority”
Now, going back to our issue (page 265): Ii is our “expert” points us in a right direction or “the unclaimed form error” is not applicable here?
Thank you
