1. Geometric Dimensioning and Tolerancing unit 5, product plans & virtual condition chapter 7, virtual condition

2. EML 2023 Department of Mechanical and Aerospace Engineering Introduction Chapter introduces an important concept related to the mating of parts in an assembly. Interchangeability of parts and assemblies can only be ensured when parts are accepted at virtual condition or better. 2

3. EML 2023 Department of Mechanical and Aerospace Engineering External Feature Suppose we’re making a clearance hole to fit over a peg. 3 How big should we make the hole to make sure we have clearance? Well, what’s the virtual size of the peg?

4. EML 2023 Department of Mechanical and Aerospace Engineering Virtual Condition 4 The virtual condition of a hole is the region that is guaranteed to be free space. The virtual condition of a peg is the region that might be occupied. If the virtual condition of the hole is larger than the virtual condition of the peg, then we are guaranteed that the hole will clear the peg.

5. EML 2023 Department of Mechanical and Aerospace Engineering 5 The virtual size of a hole will equal the diameter of the hole minus any position tolerance. Check the extreme limits.

6. EML 2023 Department of Mechanical and Aerospace Engineering 6 The virtual size of a peg will equal the diameter of the peg plus any position tolerance. Check the extreme limits.

7. EML 2023 Department of Mechanical and Aerospace Engineering Guaranteeing Part Mating The hole in the block will always clear the peg if: the virtual size of the hole (the guaranteed free space) is greater than the virtual size of the peg (the largest possible region that may be occupied by the peg). 7