2. Objective:
1. Explain the fundamental concept of
location tolerance
2. Interpret location tolerance control.
3. LOCATION TOLERANCES
DEFINITION
• Control relationship or location of the features
size (axis or center plane) with respect to
datums
• Types of location tolerances:
1. Position
2. Concentricity
3. Symmetry
4. Used to describe the perfect location of a
point, line, or plane of a feature in
relationship with datums
It applied on:
• the axis of the hole or pin and
• centerplane of slot or groove
MMC principle is applicable
POSITION
5. POSITION TOLERANCE
Cylindrical tolerance zone within which the axis
of feature is permitted to vary from true position
or basic dimensions
20
30
0.2 tol zone
0.2
10 0.1
A B C
Actual
location of
hole
6. • The derived tolerance zone for the hole centers are
round or cylinder zone which is define by the basic
dimensions
• The cylinder zone allows the same amount of deviation
in all direction. This indicate the round zone provides large
tolerance zone that to be used without loss of function of
the part < fitting or assembly >
• The total tolerance for the position is allowed to have
bonus tolerance if the hole size departed from MMC
• The position tolerance permit 360 flexibility – Datum
Shift
• Functional gage is allowed
ADVANTAGES
8. TOP THEORIES
Two theories can be used to visualize the effects of a
TOP control:
1)The virtual condition boundary theory -A theoretical
boundary limits the location of the surfaces of a FOS.
-most common in RFS TOP application
2)The axis theory -The axis (or centerplane) of a FOS
must be within the tolerance zone.
– most common in MMC tolerance of position application.
9.
10.
11.
12.
13. Inspecting TOP applied at RFS
When TOP is specified on an RFS basis, it
requires variable gaging to verify the
requirements.
A variable gage is a gage that is capable of pro-
viding a numerical reading of a part parameter.
Examples of variable gages are CMMs; special
dedicated variable gages; and standard
measuring
equipment, such as collets, height gages,
expanding mandrels, and dial indicators.
19. Inspecting TOP applied at MMC
A functional gage is a gage that verifies functional
requirements of part features as defined by the
geometric tolerances.
It does not provide a numerical reading of a part parame-
ter. A functional gage often provides a "pass" or "fail"
assessment of apart feature.
A functional gage is often referred to as an attribute gage
or a fixed gage because it checks attributes of a part
FOS (location and orientation).
20. Benefits of Functional Gages compared to Variable Gages.
The gage represents the worst-case mating
part.
Parts can be verified quickly.
A functional gage is economical to produce.
No special skills are required to "read" the
gage or interpret the results.
In some cases, a functional gage can check
several part characteristics simultaneously
21. Cartoon Gage
A cartoon gage is a sketch of a functional gage.
A cartoon gage defines the same part limits that
a functional gage would, but it does not
represent the actual gage construction of a
functional gage.
The functional gage does not exist in the design
stage, so a cartoon gage is used.
24. •Figure 2, illustrated that:
• Shape of position tolerance
• zone is diameter 0.25
• MMC principle is applied
• which allowed additional
• tolerance to be used
• Position tolerance is a
• diameter 0.25 when the holes
• are produced at MMC
• Position tolerance zone
• increases up to diameter
• 0.45, if the holes are
• produced at LMC
• The basic dimensions are
• taken from the secondary &
• tertiary datum planes (B and
• C)
Figure :
With Specified Datums, Form, and
Orientation Tolerances
25. •Before the basic dimensions
could be inspected, the
primary, secondary and
tertiary datum planes need to
be established first
• Form and orientation
tolerances had been specified
to control the
precision of the datum
features
• Datum surface A is to be
control to a flatness of 0.03
(total)
• Datum surface B is to be
perpendicular to datum plane A
within 0.03 (total)
• Datum surface C is to be
perpendicular to datum plane A
within 0.03 (total )and also
perpendicular to datum plane B
within 0.05 (total)
26. COMPOSITE VERSUS SEGMENT
When datum references are repeated in the second segment of a
composite or single segment control, the meaning is different
27. COMPOSITE POSITION TOLERANCE
When the location of a pattern of features from feature
to feature is more important than the from datum to
pattern of feature, composite position tolerance may be
used
It consists of two or more single segment of position
tolerance that used to define the location, spacing, and
orientation of a pattern of features of size
0.8 M A B C
0.2 M A
31. Floating Fastener Method
• Position tolerancing techniques are most effective
and appropriate in mating part situations
• A floating fastener assembly can consists of two
or more components with any number of
corresponding non-threaded through holes. These
components are to be fastened together with
separate components (screws/nuts)
•The calculation of their position tolerances should
be based on the two parts and their interface with
the fastener in terms of MMC sizes.
DETERMINE TOLERANCE OF MATING PARTS
32. In the following figure, two parts are to be assembled with four M5
screws. The holes in the two parts are to line up sufficiently to
pass the four screws at assembly
• Since the four screws (fasteners) are separate components,
they are considered to have some “float” with respect to one
another
• Formula used to determine the position tolerance by floating
fastener method is:
T = H – F
Where, T = position tolerance
H = hole size at MMC
F = fastener size at MMC
FLOATING METHOD
33. • Application of the MMC
principle to these position
tolerance is allowable. Thus,
guarantees functional
interchangeability, design
integrity, and maximum
production tolerance
•Functional gaging can be used
for checking these position
tolerance and provide a very
effective method of evaluation.
T = H – F
T = position tolerance
H = hole size at MMC
F = fastener size at MMC
34. • When one of two mating parts has “fixed” features, such as the
threaded studs, the Fixed Fastener Method is used in calculating
position tolerances
•These method can be applied to numerous other manufacturing
situations such as locating dowels and holes, tapped holes, etc.
• The advantages of the MMC principle can be also apply here
• However, with a fixed fastener method, the calculation of position
tolerance of mating parts is the difference between the MMC sizes
of mating features must be divided between the two features, since
the total position tolerance must be shared by the two mating
features.
FIXED METHOD FASTERNER
35. • Formula used to determine the position tolerance by fixed
fastener method is:
T = (H – F) divided by 2
Where, T = position tolerance
H = hole size at MMC
F = fastener size at MMC
In the following figure, shows the calculation of position tolerance
by fixed fastener method. In this example, the derived 0.4 was
divided equally, with 0.2 diameter position tolerance assigned to
each mating part
• However, the total tolerance of 0.4 can be distributed to the two
parts as desired, so long as the total is 0.4 ( eg. 0.3 + 0.1, 0.25 +
0.15 ). This decision is made at the design stage and must be fixed
on the drawing before release to production.
36. T = (H – F) divided by 2
T = position tolerance
H = hole size at MMC
F = fastener size at MMC
37. • When dimensioning threaded holes
or press fit holes, consideration
must be given to the variation in
perpendicularity of the axis of the
hole relative to the mating face of
the assembly.
• The squareness error of the
fastener may result in an
interference condition with the
mating part.
• An interference condition can occur
where a position tolerance is specified
for the hole, and the hole is tipped within
the position tolerance zone.
PROJECTED TOLERANCE ZONE
38. • When the fastener is placed in the hole, the
orientation of the fastener may result in an interference
condition near the head of fastener. This condition is
common with fixed fastener applications
• Where there is concern that an interference condition
may exist, due to the orientation of the fastener, a
projected tolerance zone should be used to eliminates
the interference
PROJECTED TOLERANCE ZONE
39. • A projected tolerance zone is a
tolerance zone that is projected
(extended) above the part surface.
A projected tolerance zone exists
whenever the projected tolerance
zone modifier is specified.
• The projected tolerance zone
symbol is a “P” enclosed in a
circle. Where a projected tolerance
zone is specified, the tolerance
zone is projected above the part
surface.
• The projected value is usually the
maximum thickness of the mating part
or the maximum height of the pin or
stud.
PROJECTED TOLERANCE ZONE
40. CONCENTRICITY
• Controlling the relationship between the axis of
feature size to datum axis.
• The tolerance zone for a concentricity control is three-
dimensional; it is a cylinder that is coaxial with the datum
axis.
The median points of correspondingly located elements of
the feature being controlled, regardless of feature size,
must lie within the cylindrical tolerance zone.
A median point is the midpoint of a two-point
measurement.
• Always specified as RFS
42. SYMMETRY
• Condition in which a feature is equally disposed
about the centerplane of a datum
• Always applied at RFS
SYMMETRY TOLERANCE
The tolerance zone is two parallel planes centered about a
datum axis or centerplane.
The median points of the toleranced feature must be within
the tolerance zone.
