CQI Metrology & Measurement Systems Flashcards

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

Answer: Microinch (µin) or Ra value

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

What does 'Ra' represent in surface finish measurement?

Answer: The arithmetic average of surface profile deviations from the mean line

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

A profilometer is used to measure:

Answer: Surface texture and roughness

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

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

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

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

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

Answer: Geometric dimensioning and tolerancing (GD&T) requirements

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

What does a 'flatness' tolerance control in GD&T?

Answer: How much a surface can deviate from a perfect flat plane, regardless of datum

Flatness controls how much a surface may deviate from a theoretically perfect flat plane and is a form tolerance independent of any datum.