Metrology Flashcards
slay the midterm
Metrology is…
a science of measurement
Metrology includes…
all theoretical and practical aspect of measurement
what factors determine performance of product (other than mechanical and physical properties)
dimensions and tolerances
Definition of Dimensions
linear or angular sizes of components
Definition of Tolerances
allowable variation with NO effect on performance
dimensions on part drawings represent…
nominal or basic sizes of the part
when do variations occur?
occur in any manufacturing process (manifested as variations in part size)
what are tolerances used for?
used to define limits of allowed variation
If tolerance is too small what does it cost?
it costs ALOT, cost is high
how much does tolerence shrink every 10 years
shrinks by a factor of 3
Can parts from the same machine be different?
Yes.
1. speed of operation *
2. temperature *
3. lubrication
4. difference of incoming material *
What is bilateral tolerance
Two, variation in both positive and negative direction from nominal
Unilateral Tolerance?
One, either positive OR negative
Limit dimention?
Max dimension and min dimension, tolerance is the difference.
interference fit
you have to force it (shaft bigger than hole)
Transition fit
fit with small clearance or
interference that allows for accurate location of
mating parts
(shaft and hole are practically the same)
clearance fit
smaller than hole (fits easily and allows for rotation)
what are the 3 types of tolerance
- Bilateral (balanced and unbalanced)
- Unilateral (only one)
- limit dimension (max and min dimension)
Allowance
the specific difference in
dimensions between mating parts
Basic size
dimension from which limits of
size are derived
Clearance
the space between mating parts
Datum
theoretically exact axis, point, line or
plane
Fit
the range of looseness or tightness
Interference
negative clearance