GD&T Position Tolerancing Calculations 2

Question 1

A hole has a position tolerance of ⌀0.4 at MMC. The actual hole diameter is 10.3 mm and MMC is 10.0 mm. What is the total allowable position tolerance?

Accepted Answer

⌀0.7

Answer

At MMC the tolerance is ⌀0.4; the hole is 0.3 mm larger than MMC, so bonus tolerance adds 0.3, giving ⌀0.7 total.

Question 2

For a pattern of four holes, the True Position is defined by basic dimensions from datum A (primary), B (secondary), and C (tertiary). Which datum controls orientation of the pattern?

Accepted Answer

Datum A

Answer

The primary datum (A) controls orientation — it establishes the first degree of constraint, typically perpendicularity or parallelism.

Question 3

A shaft pin has a position tolerance of ⌀0.5 at LMC. The actual pin diameter is 12.0 mm and LMC is 12.3 mm. What bonus tolerance is available?

Accepted Answer

⌀0.3

Answer

At LMC, bonus tolerance equals the amount the actual size departs from LMC: 12.3 − 12.0 = 0.3 mm added to the stated ⌀0.5.

Question 4

The formula for converting a Cartesian position deviation (Δx, Δy) to a diametral position error is:

Accepted Answer

2√(Δx² + Δy²)

Answer

The diametral true-position error = 2 × √(Δx² + Δy²), because the cylindrical tolerance zone is centered on true position.

Question 5

A hole center is measured at X = 25.08 mm and Y = 15.06 mm. Basic dimensions are X = 25.00 and Y = 15.00. What is the diametral position error?

Accepted Answer

⌀0.10

Answer

Δx = 0.08, Δy = 0.06; radial error = √(0.08² + 0.06²) = √(0.01) = 0.10; diametral = 2 × 0.05 = ⌀0.10.

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

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

GD&T Position Tolerancing Calculations 2