# How to find a dimension that isn't explicit if there are tolerances

For a part like the one shown, let's say I wanted to find the dimension labeled 3", if it wasn't already labeled. Since there are tolerances already on the part, how would I determine the 3" value along with its tolerances? Can I just add and subject the tolerances? For example, 4.00 +- 0.3 - 1.00 +-0.1 = 3.00 +- 0.2 ? What if I wanted to find the distance from the right end of the hole to the right face of the part, assuming diameter D = 1" +- 0.01? Could I simply do 3.00 +- 0.2 - (1/2) +-(0.01/2) = 3.00 +- 0.2 - 0.5 +- 0.005 = 2.5 +- 0.195? Thanks for the help!

• Your example is a case of being over-dimensioned. It has multiple dimensions that can’t always be satisfied at the same time. My question to you is why do you need the 3.0 dimension? If it’s necessary you should specify it as “reference” by putting it in parenthesis. – GisMofx Jun 20 at 1:09
• 3 would have a compound tolerance of +-0.13 – joojaa Jun 20 at 4:00
• @GisMofx the drawing makes up for over-dimensioning in the horizontal direction by not giving the hole position vertically at all. – TimWescott Jun 20 at 17:40
• @GisMofx your comment is actually a good answer, just as it is. I suggest you copy & paste it into an answer. – TimWescott Jun 20 at 17:41