GD&T Surface Finish & Assembly Requirements 3

Question 1

A shaft and hole assembly uses an interference fit. Which surface finish condition on the shaft would MOST likely cause the interference to be less than intended?

Accepted Answer

Surface peaks (asperities) that are flattened during pressing

Answer

When pressing an interference fit, surface peaks are crushed and flattened, effectively reducing the interference and the resulting holding force.

Question 2

The 'lay' of a surface texture is best described as:

Accepted Answer

The predominant direction of surface marks or tool paths

Answer

Lay refers to the predominant direction of the surface pattern, which is determined by the manufacturing process used.

Question 3

A drawing callout reads 'surface finish Ra 1.6 μm max'. A measured surface has Ra 1.2 μm. This surface is:

Accepted Answer

Within tolerance

Answer

'Max' means the Ra value must not exceed 1.6 μm; a measured value of 1.2 μm is smoother and therefore within tolerance.

Question 4

Which GD&T symbol, when applied to a surface, requires every point on that surface to fall within two parallel planes separated by the tolerance value?

Accepted Answer

Flatness

Answer

Flatness requires all surface points to lie within two parallel planes spaced by the tolerance value, with no datum reference required.

Question 5

In a bolted joint assembly, if the mating surfaces have excessive waviness (long-wavelength deviations), the primary risk is:

Accepted Answer

Uneven clamp load distribution and potential fatigue cracking

Answer

Waviness creates gaps and high-pressure contact zones in bolted joints, causing uneven clamping forces that accelerate fatigue failure.

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

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

GD&T Surface Finish & Assembly Requirements 3