ASQ CQT sample bank question
Gregory Mayrand 12016
Joined 02/07/2020 - 2 Posts
Question regarding sample bank question:
 
An assembly of three parts has an overall tolerance of plus/minus 25mm. Two of the parts have tolerances of 10mm and 15mmm each. What is the tolerance of the third component?

What is the formula or computation for this question and where can it be found in the Certified Quality Technician Handbook?                        
2 Replies
Mark Harrell 6705
Joined 04/04/2019 - 1 Posts
Maybe I am missing something obvious but using worst case method the two parts with the given tolerances of 10 and 15 have already consumed the tolerance band of the assembly at worst case meaning the 3rd component would have to be +/- 0 mm.  anything larger and the 3rd component would push the assembly over or under tolerance.  That said there are also 3 sigma methods for calculating stackup which could allow a small tolerance on the 3rd component.  I'm interested to see other replies
Gregory Mayrand 12016
Joined 02/07/2020 - 2 Posts
Hi Mark, oddly enough the answer is 17 mm. The method for solving is the squares root of the sum of the squares however, I get 18 when I perform this operation. I'm hoping I can get this figured out before I attempt the test.