GD&T Position Tolerancing Calculations 3

Question 1

A hole is located at basic X = 40.00, Y = 30.00. The CMM measures the hole axis at X = 40.05, Y = 29.96. What is the diametral position error?

Accepted Answer

⌀0.128

Answer

Δx = 0.05, Δy = 0.04; radial = √(0.0025 + 0.0016) = √0.0041 ≈ 0.064; diametral = 2 × 0.064 ≈ ⌀0.128.

Question 2

What does the term 'virtual condition' mean for an internal feature (hole) controlled with position at MMC?

Accepted Answer

MMC size minus the position tolerance

Answer

For an internal feature, virtual condition = MMC size − position tolerance, representing the worst-case boundary for assembly.

Question 3

A pin (external feature) has MMC = 12.0 mm and a position tolerance of ⌀0.3. What is its virtual condition?

Accepted Answer

12.3 mm

Answer

For an external feature, virtual condition = MMC + position tolerance = 12.0 + 0.3 = 12.3 mm.

Question 4

Projected tolerance zone is specified because:

Accepted Answer

It controls the zone where a fastener extends outside the part, preventing interference at assembly

Answer

A projected tolerance zone extends the positional control above the hole to where mating fasteners or studs will reside, preventing angular stack-up issues.

Question 5

If a position callout reads ⌀0.25 (M) with a projected tolerance of 15 mm, what does '15' represent?

Accepted Answer

The minimum projection height above the part surface

Answer

The projected tolerance zone height (15 mm) specifies how far the cylindrical zone extends beyond the part surface to capture fastener axis deviation.

(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test

(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test

GD&T Position Tolerancing Calculations 3