GD&T Surface Finish & Assembly Requirements 5

Question 1

A threaded fastener hole drawing calls out a perpendicularity tolerance of 0.1 mm for the hole axis relative to the mounting surface. This ensures:

Accepted Answer

The bolt will not induce bending stress on the mating flange

Answer

Perpendicularity of the threaded hole to the mounting surface ensures the bolt pulls straight, preventing bending moments that could cause fatigue failure in the flange.

Question 2

What does the sampling length (cutoff wavelength λc) determine in surface roughness measurement?

Accepted Answer

The wavelength boundary separating roughness from waviness

Answer

The cutoff wavelength λc is a filter setting that separates short-wavelength roughness from longer-wavelength waviness in surface measurements.

Question 3

A sealing surface for an O-ring groove must have Ra between 0.8 μm and 1.6 μm. A measured Ra of 0.4 μm would be:

Accepted Answer

Out of tolerance because it falls below the minimum Ra

Answer

O-ring grooves require a minimum roughness so the elastomer can grip the surface; a surface that is too smooth can allow the O-ring to extrude or roll out.

Question 4

In ASME Y14.5, which condition applies when a feature of size is at its maximum material condition (MMC) and a geometric tolerance is at its least restrictive?

Accepted Answer

Maximum Material Condition (MMC) modifier (circle M)

Answer

The MMC modifier (⊕M) allows the geometric tolerance to increase as the feature departs from MMC toward LMC, providing bonus tolerance for assembly clearance.

Question 5

A component drawing requires a surface finish of Ra 0.8 μm on a mating face. The manufacturing engineer proposes lapping instead of grinding. This is acceptable if:

Accepted Answer

Lapping can achieve Ra 0.8 μm and no process restriction is noted

Answer

Without a specified process restriction on the surface symbol, any process that achieves the required Ra value is acceptable per drawing intent.

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

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

GD&T Surface Finish & Assembly Requirements 5