1. Dimension Application and Limits of Size4
Dimension Application and Limits of Size

2. Calculate and apply limits of size for mating features.
Clearly apply dimensions by complying with the stated general dimensioning guidelines.
Apply dimensions to any of the geometric shapes commonly found on mechanical parts.
Cite the categories for limits of fit and describe the general condition created by each category.
Calculate and apply limits of size for mating features.
Cite the two rules contained within ASME Y14.5.
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3. Provide examples of the effects that dimensions and tolerances have on manufacturing.
Complete a surface condition specification when provided the allowable variations.
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4. Cylinders Diameter and length required
Prefer dimensions on noncircular view
Diameter dimension usually between the views
Only one view may be necessary
Diameter symbol required for circular dimension
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5. Cones Right circular cone Oblique circular cone
Base diameter and cone height
Base diameter and cone angle
Oblique circular cone
Base diameter, cone height, apex offset
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6. Holes—Specifying Diameter
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7. Holes—Specifying Location
Hole center
Centerlines and extension lines used
Centerlines between holes
Extension lines beyond holes
Dimensions on one side of view
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8. Holes—Specifying Depth
Assumed to go through part, unless depth is specified
When not clear, use THRU
Use depth symbol for blind holes
Depth specified after the diameter
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9. Holes for Machine Screws—Counterbore
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10. Holes for Machine Screws—Countersink
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11. Angles Angle specification notation
Degrees—30
Minutes—3015
Seconds—301528
Decimal—30.25
Center of dimension line arc at vertex of angle
Extension lines, if extended, intersect at vertex of angle
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12. Chamfers Eliminates sharp edge Facilitates assembly
45° chamfers may be dimensioned by a note
Dimensioning chamfers other than 45°
Dimension angle and length of one side
Dimension lengths of both sides of chamfer
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13. Taper—Standard Specified
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14. Taper—Taper per Inch Specified
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15. Taper—Included Angle Specified
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16. Features on Curved Surfaces
Location
Angle
Chord
Arc length
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17. Spherical Radii SR in front of dimension Dimension to outside surface
Easier to produce
Easier to verify
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18. Irregular Curves
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19. Symmetrical Features
Only one side of symmetry line requires dimensions
Two short lines across each end of center line indicates line of symmetry
Partial or half views allowed
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20. Machining Reliefs
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21. Threads Minimum information Example .750-10UNC-2A Nominal size
Threads per inch
Thread form
Thread class
Example
UNC-2A
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22. Knurls Machined on cylindrical shapes
Increase friction between parts
Improve grip and appearance
Diametral pitch and shape required
Diameter before knurl required
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23. Sheet Metal Bends Locate surface intersections or intersecting faces
Specify inside or outside bend radius, but not both
Material type and thickness dictates undimensioned bend radius
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24. Sheet Metal Joggles Information needed Location Height Length
Bend radius
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25. Standard Sizes and Shapes
Reduces production costs
Dimensions not needed for standard materials
National standards maintain uniformity
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26. Broken Lengths Long parts have portion removed Reduces drawing space
Dimension not broken
Dimension value reflects complete part
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27. Limits of Size General tolerance in notes acceptable
Tolerance on size dimension
Limit dimensions
Bilateral tolerances
Unilateral tolerances
Single limit tolerances
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28. Limit Dimensions Specifies minimum and maximum
Maximum size above minimum
In a note, minimum size before maximum
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29. Plus and Minus Tolerances
May be bilateral or unilateral
Bilateral tolerance may be equal or unequal
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30. Single Limit Dimensions
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31. Tolerances on Angles Limit dimensions Plus-and-minus tolerances
Orientation tolerances
Single limit not practical
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32. Basic Hole System Preferred system
Limits of size for hole calculated first
Typically use standard tool sizes for hole
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33. Basic Shaft System May require nonstandard tools for hole
Used when purchasing shaft and mating hole is specified
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34. Calculating Size Limits Using Standard Tables
Function of parts considered
Descriptions of general applications provided
Determine class of fit
Determine tolerance values
Tolerance is proportional to size of feature
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35. Running and Sliding Clearance Fits
Parts move freely
9 classes of fit
RC1 through RC9
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36. Location Clearance Fits
Locating parts without interference
11 classes of fit
LC1 through LC11
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37. Location Transition Fits
Locating parts with slight clearance or interference
6 classes of fit
LT1 through LT6
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38. Location Interference Fits
Locating parts with a press fit (interference)
Not for transmitting loads
3 classes of fit
LN1 through LN3
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39. Force Fits Locating parts with a press fit (interference)
Bore pressure constant through range
5 classes of fit
FN1 through FN5
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40. Limit Calculations Using Tables
Select a class of fit
Select a category of fit from the class
Find appropriate tolerance table
Locate nominal size in table
Calculate tolerances
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41. Rules in ASME Y14.5 Rule #1: Perfect form at MMC Exceptions to Rule #1
Parts subject to free state variations
Stock materials
Rule #2: RFS and RMB assumed
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42. Dimension Interpretations
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43. Machine Capability Each machine type is uniquely capable
Each machining program for a part is uniquely capable
Smaller tolerances generally equal larger costs
Know your company and supplier’s capabilities
Machining handbooks provide general capabilities
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44. Dimension Revision Change geometry in CAD
Out-of-scale dimension to be avoided
Reasons for revisions
Design changes
Corrections
Manufacturing-based changes
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45. Surface Texture Dimensions
Determined by function
Surface variations
Roughness
Waviness
Lay
Roughness width
Roughness width cutoff
Roughness cutoff
Sampling length
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46. Surface Texture Symbols
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47. Explain how a single view can be dimensioned to completely define a cylindrical part.
Create one view that shows both the length and diameter of the cylinder and apply both the length and diameter dimensions to the created view.
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48. List the classes of fit.
Running and sliding clearance, location clearance, location transition, location interference, force fits
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49. (Max clearance comes from tol table)
Calculate the tolerance for a hole that will accept a purchased shaft with the dimension .5.001, and provide a clearance of min .0012, max (RC6).
Min hole = = .5022
Max hole = = .5028
(Max clearance comes from tol table)
hole tol + min clearance + shaft tol
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50. How can an exception to Rule #1 be specified?
Place the independency symbol adjacent to the excepted dimensions to indicate perfect form at MMC is not required.
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51. What is assumed in Rule #2?
Regardless of feature size and regardless of material boundary.
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52. What is the effect of using very small size tolerances on holes?
Smaller tolerances can force the use of more closely controlled manufacturing processes which will increase costs.
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53. Surface roughness and roughness cutoff
Often, what are the only numerical values specified in a surface texture dimension?
Surface roughness and roughness cutoff
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54. Apex offset, cone Arc tangents Base diameter, cone
The distance from the apex of a cone to a line extending perpendicular to and from the center of the cone base.
Arc tangents
The point on an arc where a straight line extended to infinity will touch the arc only once.
Base diameter, cone
The distance across the bottom of a cone.  
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55. Basic hole system Basic shaft system Bilateral tolerance
A system for calculating the limits of size for a mating hole and shaft. The size limits for the hole are calculated first, and the size limits for the shaft are based on the hole dimensions.
Basic shaft system
A system for calculating the limits of size for a mating hole and shaft. The size limits for the shaft are calculated first, and the size limits for the hole are based on the shaft dimensions.
Bilateral tolerance
The allowable variance that permits equal or unequal positional tolerance in both directions.
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56. Blind hole Centerdrill
A hole that does not go all the way through the material in which it exists.
Centerdrill
A tool used to produce a combined drilled hole and countersink. The center-drilled hole produced with this tool is used to mount the workpiece on a machine center.
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57. Combined drill and countersink
Centerdrilled hole
A hole and countersink cut into the end of a shaft or other cylindrical feature.
Combined drill and countersink
Also known as a centerdrill. A special tool used for centerdrilling processes.
Cone height
The distance from the base to the apex of a cone.
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58. Counterbore Countersink Diameter
A stepped increase in the diameter of a hole. Counterbores are located at the ends of holes.
Countersink
An angular increase in the size of a hole. A countersink has the shape of a right circular cone and is coaxial with the hole.
Diameter
The distance across a circle measured on a line that passes through the center.
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59. Feature of size
Generally, a single feature or group of features defining a single shape that affects the weight of a part if its dimension is changed. As an example, changing a hole diameter affects how much material is in the part, thereby affecting the weight of the part. There are two classes for features of size: regular and irregular.
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60. Irregular features of size
Hole diameter
The minimum acceptable amount of information for a spotface hole.
Irregular features of size
An enclosed shape or a collection of features that in combination establish a boundary. The shape may be a closed boundary such as a D-shaped hole that has a profile tolerance applied, or it may be a shape such as a cylinder that is inscribed within and tangent to three pins.
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61. Joggle
An offset in an extension line that can be used to provide clearance between the extension line and other lines or symbols.
Keyseat
A rectangular slot cut in a shaft or hub for the purpose of installing a key to lock rotational relationships between parts.
Lay
The direction of surface irregularities caused by machining processes.
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62. Minor radius, countersink
Limit dimension
A dimension that shows the minimum and maximum allowable values for a feature size or location.
Minor radius, countersink
The shortest distance between the axis of a hole and the intersection of the countersink with an irregular curved surface.
Parallelepiped
A six-sided prism where all surface intersections form 90° angles.
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63. Regular features of size
Typically one part feature that is associated with a single size dimension such as thickness, width, length or diameter.
Removed view
A copy of a portion of a view, used to prevent cluttered or repetitive dimensions.
Revisions
Changes made after a drawing is released.
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64. Right square pyramid Roughness
A pyramid with its apex located on a line that is perpendicular to and centered on the base.
Roughness
The small peaks and valleys on a surface that are caused by manufacturing processes.
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65. Roughness cutoff, roughness width cutoff, and sampling length
The specified distance across a surface used to determine the surface's roughness.
Roughness width
The distance across the peaks and valleys that cause surface roughness.
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66. Sharp diameter, flathead screw
The diameter created by extending the screw head cone all the way to the top of the head.
Single limit dimension
A dimension that only shows one acceptable limit. The other limit must be controlled by the geometry of the part.
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67. Spotface diameter Surfaces Tolerance
The distance across the circular shape of a spotface, passing through the spotface's center.
Surfaces
The flat, cylindrical, and undefined faces of a part.
Tolerance
The acceptable dimensional variation that is permitted on a part.
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68. Unilateral tolerance Waviness
The allowable variance of a dimension when one of the limits is equal to the dimension.
Waviness
Large surface variations on which roughness variations may be superimposed.
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