Position Tolerancing Calculations Flashcards

In a 3D tolerance stack, three features contribute ±0.10, ±0.15, and ±0.20 positional deviations along the same axis. What is the worst-case total deviation?

Answer: ±0.45

Worst-case (arithmetic) stack = 0.10 + 0.15 + 0.20 = ±0.45 mm along that axis.

Using RSS (Root Sum of Squares) for the same three deviations (±0.10, ±0.15, ±0.20), the statistical tolerance is approximately:

Answer: ±0.27

RSS = √(0.10² + 0.15² + 0.20²) = √(0.01 + 0.0225 + 0.04) = √0.0725 ≈ ±0.27 mm.

A pattern of 6 holes must assemble with 6 clearance fasteners. MMC of holes = 10.0 mm, fastener MMC = 9.6 mm. Using the fixed fastener formula, the position tolerance is:

Answer: ⌀0.4

Fixed fastener tolerance = (MMC_hole − MMC_fastener) / 1 = 10.0 − 9.6 = 0.4; split between two mating parts gives ⌀0.2 each, but for a single part: ⌀0.4.

For a floating fastener assembly, the position tolerance formula is:

Answer: T = (H − F) / 2

Floating fastener formula: each part gets T = (H_MMC − F_MMC) / 2, splitting the clearance equally between both mating parts.

A true position callout without any modifier defaults to which condition under ASME Y14.5-2018?

Answer: RFS

Under ASME Y14.5-2018, RFS is the default implied condition when no modifier symbol (M or L) is shown.

A position tolerance is given as ⌀0.5 with datum B at MMC. If datum feature B (a pin) measures 14.8 mm and its MMC is 15.0 mm, what is the datum shift available?

Answer: 0.2 mm

Datum shift = MMC_datum − actual_datum = 15.0 − 14.8 = 0.2 mm, which may be used to relax the positional requirement.

A bolt circle of 8 holes equally spaced on a ⌀100 mm bolt circle has a position tolerance of ⌀0.3. What basic angular spacing is used between adjacent holes?

Answer: 45°

360° ÷ 8 holes = 45° basic angular spacing between each adjacent hole on the bolt circle.