CQI CQI Metrology & Measurement Systems 3

Question 1

What unit is commonly used to express surface roughness in the US?

Accepted Answer

Microinch (µin) or Ra value

Answer

In the US, surface roughness is commonly expressed in microinches (µin) using the Ra arithmetic average roughness parameter.

Question 2

What does 'Ra' represent in surface finish measurement?

Accepted Answer

The arithmetic average of surface profile deviations from the mean line

Answer

Ra is the arithmetic average roughness, calculated as the mean absolute deviation of surface profile heights from the centerline.

Question 3

A profilometer is used to measure:

Accepted Answer

Surface texture and roughness

Answer

A profilometer (contact or optical) is the standard instrument for measuring surface texture and roughness parameters.

Question 4

What is the purpose of a coordinate measuring machine (CMM)?

Accepted Answer

To measure three-dimensional geometry of a part against its design specifications

Answer

A CMM uses a probe to measure three-dimensional coordinates of points on a workpiece to verify geometric tolerances against design requirements.

Question 5

On an engineering drawing, a feature control frame is used to specify:

Accepted Answer

Geometric dimensioning and tolerancing (GD&T) requirements

Answer

A feature control frame is the standard method for specifying GD&T requirements including form, orientation, location, and positional tolerances.

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