Exam 1 Review Flashcards
Heavy dark line that divides part view to expose internal geometries
Sectional line
Reference features usually defined by the critical surfaces on a part. These surfaces will be the origin for
dimensioning other features.
Datum
In the three-plane datum system, the primary (first) datum constrains _____ degree(s) of freedom
3
In the three-plane datum system, the secondary (second) datum constrains _____ degree(s) of freedom
2
In the three-plane datum system, the tertiary (third) datum constrains _____ degree(s) of freedom
1
In the three-plane datum system, the primary (first) datum constrains which degrees of freedom?
1 translation in Z
1 rotation in u
1 rotation in v
In the three-plane datum system, the secondary (second) datum constrains which degrees of freedom?
1 translation in X
1 rotation in w
In the three-plane datum system, the tertiary (third) datum constrains which degrees of freedom?
1 translation in Y
In the three-plane datum system, the primary (first) datum has a minimum of _____ point contact
3
In the three-plane datum system, the secondary (second) datum has a minimum of _____ point contact
2
In the three-plane datum system, the tertiary (third) datum has a minimum of _____ point contact
1
Theoretically, the exact size we would prefer
Basic Size
Maximum and minimum dimensions acceptable
Limits of size
Total amount of variation about the Basic Size we can “tolerate”
Total tolerance
The intended difference in size of mating parts
Allowance
Specifying the maximum and minimum dimensions only
Limit dimensioning
Specifying the basic size +/- tolerance values
“Plus and Minus” Dimensioning
There is always space (The hole is larger than the cylinder)
Clearance fit
There is never space (The hole is smaller than the cylinder)
Interference fit
There may be a space or there may be interference
Transition fit
Comparing an unknown quantity to a known standard
Measurement
Examining a part to evaluate its conformity to design
Inspection
Determining if a part or feature meets the design specifications
Gaging
If I have a measurement instrument, what aspects of the instrument do I care about?
Resolution
Stability
When a measurement device is
checked against a known standard
Calibration
Examples of known standards
Gauge blocks, gauge pins
Government standards (NIST)
Linear measurement is an inspection by
variables
Gaging instruments are an inspection by
attributes
Provides information about the characteristics of the part
and the process but is often slow and cumbersome
Measuring
Can be much quicker but provides less information about the part and fabrication process
Gaging
There is _____ in all measurements
variability
The variation in measurement when:
* Using one measurement
instrument
* Used by the same operator
* Measuring the same
characteristics of a part
Repeatability (Measurement Variation)
Multiple operators:
* Using the same measuring
instrument
* Measuring the same
characteristics of a part
Reproducibility (Operator Variation)
Used in nondestructive tests
Crossed R&R Study
Used in destructive testing
Nested R&R Study
We have to make the assumption the parts are reasonably ______ in Gage R&R studies
Homogeneous
The operator measurement mean deviates from the actual
part dimension
Accuracy
Potential causes of accuracy
- Lack of calibration
- Thermal effects
Variations caused by
changes over time
periods
Measurement Stability
Accuracy of an instrument
over the entire range of
measurement
Linearity
Considered the modern approach to dims and tolerance
Geometric Dimensioning and Tolerancing
Form Tolerances
Straightness
Flatness
Circularity
Cylindricity
Orientation Tolerances
Angularity
Perpendicularity
Parallelism
Primary Datum: Planar surface that fixes the _____ orientation of the part
Spatial
Secondary Datum: Planar surface that fixes the _____ orientation of the part
Planar
Tertiary Datum: Planar surface that fixes the _____ location of the part
Planar
