1. ANADOLU U N I V E R S I T Y ENM202 Industrial Engineering Department
Lecture 3 – Dimensions, Tolerances and Surfaces
Spring 2007
Saleh AMAITIK

2. Tolerance & Surfaces Affected Areas Product Design Quality Control
Manufacturing Processes
Affected Areas
Tolerance & Surfaces
Product Design
Quality Control
Manufacturing
Spring 2005

3. Dimensions, Tolerances and Surfaces
Manufacturing Processes
Dimensions, Tolerances and Surfaces
In addition to mechanical and physical properties, other factors that determine the performance of a manufactured product include:
Dimensions - linear or angular sizes of a component specified on the part drawing.
Tolerances - allowable variations from the specified part dimensions that are permitted in manufacturing.
Surfaces - surface finishes obtained by manufacturing process that produce the shape
Spring 2005

4. Manufacturing Processes
Dimensions
A dimension is "a numerical value expressed in appropriate units of measure and indicated on a drawing and in other documents along with lines, symbols, and notes to define the size or geometric characteristic, or both, of a part or part feature"
Dimensions on part drawings represent nominal or basic sizes of the part and its features.
The dimension indicates the part size desired by the designer, if the part could be made with no errors or variations in the manufacturing process
Spring 2005

5. Manufacturing Processes
Tolerances
A tolerance is "the total amount by which a specific dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits"
Variations occur in any manufacturing process, which are manifested as variations in part size
Tolerances are used to define the limits of the allowed variation
Spring 2005

6. The smaller the tolerance the more expensive the part
Manufacturing Processes
Why is tolerancing necessary?
It is impossible to manufacture a part to an exact size or geometry
Assemblies: Parts will often not fit together if their dimensions do not fall within a certain range of values
Tolerances are needed to control the dimensions of any two mating parts so that any two parts may be interchangeable.
Tolerances on parts contribute to the expense of a part,
The smaller the tolerance the more expensive the part
Spring 2005

7. Manufacturing Processes
Types of Tolerances
A Dimensional tolerance is the total amount a specific dimension is permitted to vary, which is the difference between maximum and minimum permitted limits of size.
A Geometric tolerance is the maximum or minimum variation from true geometric form or position that may be permitted in manufacture.
Geometric tolerance should be employed only for those requirements of a part critical to its functioning or interchangeability.
Spring 2005

8. How Is Tolerance Specified?
Manufacturing Processes
How Is Tolerance Specified?
Tolerances can be expressed in Several ways:
General Tolerances
A note may be placed on the drawing which specifies the tolerance for all dimensions except where individually specified
ALL DECIMAL DIMENSIONS TO BE HELD TO ±0.020
Specific Tolerances
The tolerance for a single dimension may be specified with the dimension based on one of the following methods
Limits
Unilateral tolerance
Bilateral tolerance
Spring 2005

9. Specific Tolerances Limit Dimensions Manufacturing Processes
Permissible variation in a part feature size, consisting of the maximum and minimum dimensions allowed
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10. Specific Tolerances Unilateral Tolerance Manufacturing Processes
Variation from the specified dimension is permitted in only one direction,
either positive or negative, but not both.
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11. Specific Tolerances Bilateral Tolerance Manufacturing Processes
Variation is permitted in both positive and negative directions from
the nominal dimension.
It is possible for a bilateral tolerance to be unbalanced; for example, ,
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12. Dimensional Tolerances (Size)
Manufacturing Processes
Dimensional Tolerances (Size)
Angular size dimension tolerance
It specifies the allowable variation on the size or gap formed by two angular elements of the shape.
Curved dimension tolerance
It is a tolerance on a dimension for a curved feature element measured along the entire path of the curve
Diameter dimension tolerance
It is the allowable variation of the size of a hole in a feature.
Spring 2005

13. Dimensional Tolerances (Size)
Manufacturing Processes
Dimensional Tolerances (Size)
Radial dimension tolerance
It is the allowable variation for the radial distance from the center of a feature circular curve to a point on the curve.
Location dimension tolerance
It is the allowable variation in locating one feature of a point with respect to another.
Angular dimension tolerance
It defines the allowable variation in the angle between two elements of a feature.
Spring 2005

14. Geometrical Tolerances (Form)
Manufacturing Processes
Geometrical Tolerances (Form)
Spring 2005

15. Geometrical Tolerances (Form)
Manufacturing Processes
Geometrical Tolerances (Form)
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16. Geometrical Tolerances (Form)
Manufacturing Processes
Geometrical Tolerances (Form)
Spring 2005

17. Geometrical Tolerances (Form)
Manufacturing Processes
Geometrical Tolerances (Form)
Spring 2005

18. Geometrical Tolerances (Location)
Manufacturing Processes
Geometrical Tolerances (Location)
Spring 2005

19. Geometrical Tolerances (Location)
Manufacturing Processes
Geometrical Tolerances (Location)
Spring 2005

20. Geometrical Tolerances (Orientation)
Manufacturing Processes
Geometrical Tolerances (Orientation)
Spring 2005

21. Geometrical Tolerances (Orientation)
Manufacturing Processes
Geometrical Tolerances (Orientation)
Spring 2005

22. Geometrical Tolerances (Orientation)
Manufacturing Processes
Geometrical Tolerances (Orientation)
Spring 2005

23. Geometrical Tolerances (Orientation)
Manufacturing Processes
Geometrical Tolerances (Orientation)
Spring 2005

24. Geometrical Tolerances (Orientation)
Manufacturing Processes
Geometrical Tolerances (Orientation)
Spring 2005

25. Manufacturing Processes
Tolerance Grades
The tolerance of size is normally defined as the difference between th upper and lower dimensions. ISO 286 implements 20 grades of accuracy to satisfy the requirements of different industries.
Production of gauges and instruments.
IT01,   IT0,   IT1,   IT2,   IT3,   IT4,  IT5,  IT6.
Precision and general Industry.
IT 5,   IT6,   IT7,  IT8,  I9,  IT10,  IT11,  IT12.
Semi finished products
IT11,   IT14,   IT15,   IT16.
Structural Engineering
IT16,   IT17,  IT18 .
Spring 2005

26. Manufacturing Processes
ISO Tolerance Band "T "micrometres = (m-6) based on ISO 286  IT Grades 1 to 14  
Spring 2005

27. Fits between Mating Parts
Manufacturing Processes
Fits between Mating Parts
Fit is the general term used to signify the range of Looseness and Tightness
of mating parts
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28. Important Terms Manufacturing Processes
Nominal size: a dimension used to describe the general size.
Basic size: the theoretical size used as a starting point for the application of tolerances.
Actual size: the measured size of the finished part after machining.
Limits: the maximum and minimum sizes shown by the toleranced dimension
Allowances: the minimum clearance or maximum interference between parts, or the tightest fit between two mating parts.
Tolerance (Tolerance zone): the total allowable variation in a dimension; the difference between the upper and lower limits
Spring 2005

29. Tolerancing Holes and Shafts
Manufacturing Processes
Tolerancing Holes and Shafts
Preferred fits: A specified system of fits for
holes and shafts for SI units
- Hole basis
The minimum hole size equals the basic hole size
Uses the symbol “H” in the tolerance specification
- Shaft basis
The maximum shaft size equals the basic shaft size
Uses the symbol “h” in the tolerance specification
Spring 2005

30. The most common types of fit found in industry
Manufacturing Processes
Fits Types
The most common types of fit found in industry
Clearance Fit occurs when two toleranced mating parts will always leave a space or clearance when assembled.
Interference Fit occurs when two toleranced mating parts will always interfere when assembled.
Transition Fit occurs when two toleranced mating parts are sometimes an interference fit and sometimes a clearance fit when assembled.
Spring 2005

31. Manufacturing Processes
Clearance and Interference fits between two Shafts and a Hole
Spring 2005

32. Manufacturing Processes
Transition fit between a Shaft and a Hole
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33. Fit Type Determination
Manufacturing Processes
Fit Type Determination
If feature A of one part is to be inserted into or mated with feature B of another part, the type of fit can be determined by the following:
The Loosest Fit is the difference between the smallest feature A and the largest feature B.
The Tightest Fit is the difference between the largest feature A and the smallest feature B.
Spring 2005

34. Manufacturing Processes
ISO Tolerances for Holes (ISO 286-2)
Spring 2005

35. Manufacturing Processes
ISO Tolerances for Shafts (ISO 286-2)
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36. Manufacturing Processes
Recommended Fits
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37. Some manufacturing processes are more accurate than others Examples:
Tolerances and Manufacturing Processes
Some manufacturing processes are more accurate than
others
Examples:
Most machining processes are quite accurate, capable of tolerances = 0.05 mm or better
Sand castings are generally inaccurate, and tolerances of 10 to 20 times those used for machined parts must be specified
Spring 2005

38. Manufacturing Processes
Manufacturing Processes associated with ISO IT Tolerance Grade
Spring 2005

39. Manufacturing Processes
Metric Symbols of Fits
Spring 2005

40. Creating a Clearance Fit using The Basic Hole System
Manufacturing Processes
Creating a Clearance Fit using The Basic Hole System
Given the following fit Φ40 – H11/c11
From table for hole diameter = 40 and H11 we find
Upper deviation = +160 μm & Lower deviation = 0
From table for shaft diameter = 40 and c11 we find
Upper deviation = -120 μm & Lower deviation = μm
Calculations of dimension limits for hole and shaft
Maximum hole diameter = = mm
Minimum hole diameter = = 40 mm
Maximum shaft diameter = 40 +(-120) = mm
- Minimum shaft diameter = 40 + (-280) = mm
Maximum clearance = Maximum hole diameter – Minimum shaft diameter
= – = 0.44 mm
Minimum clearance = Minimum hole diameter – Maximum shaft diameter
= 40 – = 0.12 mm
Allowances = minimum clearance = 0.12 mm = 120 μm
Spring 2005

41. Creating an Interference Fit using The Basic Hole System
Manufacturing Processes
Creating an Interference Fit using The Basic Hole System
Given the following fit Φ40 – H7/s6
From table for hole diameter = 40 and H7 we find
Upper deviation = +25 μm & Lower deviation = 0
From table for shaft diameter = 40 and s6 we find
Upper deviation = +59 μm & Lower deviation = +43 μm
Calculations of dimension limits for hole and shaft
Maximum hole diameter = = mm
Minimum hole diameter = = 40 mm
Maximum shaft diameter = = mm
- Minimum shaft diameter = = mm
Maximum interference = Maximum shaft diameter – Minimum hole diameter
= – 40 = mm
Minimum interference = Minimum shaft diameter – Maximum hole diameter
= – = mm
Allowances = maximum interference = mm = 59 μm
Spring 2005

42. Nominal surface - intended surface contour of
Manufacturing Processes
Surfaces
Nominal surface - intended surface contour of
part, defined by lines in the engineering drawing
The nominal surfaces appear as absolutely straight lines, ideal circles, round holes, and other edges and surfaces that are geometrically perfect
Actual surfaces of a part are determined by the
manufacturing processes used to make it
The variety of manufacturing processes result in wide variations in surface characteristics
Spring 2005

43. Why Surfaces are important
Manufacturing Processes
Why Surfaces are important
Aesthetic reasons.
Surfaces affect safety.
Friction and wear depend on surface characteristics.
Surfaces affect mechanical and physical properties.
Assembly of parts is affected by their surfaces.
Spring 2005

44. Concerned with: Defining the characteristics of a surface
Manufacturing Processes
Surface Technology
Concerned with:
Defining the characteristics of a surface
Surface texture
Surface integrity
Relationship between manufacturing processes and characteristics of resulting surface
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45. Manufacturing Processes
A magnified cross‑section of a typical metallic part surface
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46. The topography and geometric features of the surface
Manufacturing Processes
Surface Texture
The topography and geometric features of the surface
When highly magnified, the surface is anything but
straight and smooth. It has roughness, waviness, and
flaws
It also possesses a pattern and/or direction resulting
from the mechanical process that produced it
Spring 2005

47. Surface Integrity Manufacturing Processes
Concerned with the definition, specification, and control of the
surface layers of a material (most commonly metals) in
manufacturing and subsequent performance in service.
Manufacturing processes involve energy which alters the part
surface.
The altered layer may result from work hardening (mechanical
energy), or heating (thermal energy), chemical treatment, or even
electrical energy
Surface integrity includes surface texture as well as the altered
layer beneath
Spring 2005

48. Four elements of surface texture
Manufacturing Processes
Four elements of surface texture
Roughness - small, finely‑spaced deviations from nominal surface determined by material characteristics and process that formed the surface
Waviness - deviations of much larger spacing; they occur due to work deflection, vibration, heat treatment, and similar factors
Roughness is superimposed on waviness
3. Lay - predominant direction or pattern of the surface texture
4. Flaws - irregularities that occur on the surface
Includes cracks, scratches, inclusions, and similar defects in the surface.
Spring 2005

49. Surface Roughness and Surface Finish
Manufacturing Processes
Surface Roughness and Surface Finish
Surface roughness - a measurable characteristic based on roughness deviations
Surface finish - a more subjective term denoting smoothness and general quality of a surface
In popular usage, surface finish is often used as a synonym for surface roughness
Both terms are within the scope of surface texture
Spring 2005

50. Surface Roughness Manufacturing Processes
Average of vertical deviations from nominal surface over a specified surface length
Surface roughness can be approximately calculated using the following equation
where
Ra = average roughness;
yi = vertical deviations (absolute value) identified by subscript i; and
n = number of deviations included in Lm
Spring 2005

51. Surface texture alone does not completely describe a surface
Manufacturing Processes
Surface Integrity
Surface texture alone does not completely describe a surface
There may be metallurgical changes in the altered layer beneath the surface that can have a significant effect on a material's mechanical properties
Surface integrity is the study and control of this subsurface layer and the changes in it that occur during processing which may influence the performance of the finished part or product
Spring 2005

52. Manufacturing Processes
Surface and Manufacturing Processes
Some processes are inherently capable of producing better surfaces than others
In general, processing cost increases with improvement in surface finish because additional operations and more time are usually required to obtain increasingly better surfaces
Processes noted for providing superior finishes include honing, polishing, and superfinishing
Spring 2005

53. Manufacturing Processes
Surface Roughness Produced by common Manufacturing Processes
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54. Surface Roughness and Production Cost
Manufacturing Processes
Surface Roughness and Production Cost
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55. Surface Roughness and Production Time
Manufacturing Processes
Surface Roughness and Production Time
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56. Measurements require Precision and Accuracy.
Manufacturing Processes
Metrology
Science of physical measurement applied to variables such as dimensions, surface finish, and mechanical and physical properties.
Measurements require Precision and Accuracy.
Precision is the degree which the instrument gives repeated measurements of the same standard.
Accuracy is the degree of agreement of the measured dimension with its true magnitude.
Sensitivity is the smallest difference in dimensions that the instrument can detect or distinguish.
Stability – The instrument’s capability to maintain its calibration over a period of time
Spring 2005