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![Dimensioning guidelines
3
5
5
3
5
3
5
2
1. Don’t overdefine or underdefine the object.
[MOST IMPORTANT]
2. Dimension to the visible contour or shape of
the feature / Don’t dimension to hidden lines.
4. Don’t dimension to object lines (model
edges), use extension lines.
5. Don’t overlap a dimension and the model.
Place dimensions away
from the model’s surface.
6. Don’t cross extension lines if possible.
7. Group dimensions when possible unless it
become difficult to read.
8. Place dimensions on the side of the view
were adjacent views exist
(for easy referencing).](https://image.slidesharecdn.com/engggraphics-250725055615-13f706ae/85/engineering-graphics-unit-planes-solid-shapes-35-320.jpg)
![“Basic Hole” Tolerancing Example
1.0000
+ .0012
- .0000
1.0000
- .0008
- .0016
Drawing shows 1 in. nominal, ANSI RC4 clearance fit
“Basic Hole” means smallest possible hole = nominal, then size shaft for
clearance
RC4 clearance = [0.0008, 0.0028] = [smallest hole-largest shaft,
largest hole - smallest shaft]](https://image.slidesharecdn.com/engggraphics-250725055615-13f706ae/85/engineering-graphics-unit-planes-solid-shapes-57-320.jpg)
engineering graphics unit planes,solid ,shapes
- 1. A Brief Introductionto Engineering Graphics
- 2. Opening comments • Engineeringgraphics is the method for documenting a design • Mechanical engineering students must be familiar with standards of engineering graphics as it is expected in industry • This set of slides introduces some of the basics, but is not comprehensive • For more, see • Engineering Graphics section on the Resources page of the course ME2011 website • Any engineering graphics textbook
- 3. 1. SHAPE 2. SIZE 3.MATERIAL 4. TOLERANCE 5. FINISH Documenting a part requires...
- 4. Engineering drawings • Universallanguage • Conventions (drawing grammar) simplify communication; your drawing is at risk if you defy • CAD packages make formal drawing easy…if you follow the conventions • The machinist will laugh at you behind your back if you show up with a non-standard drawing
- 5.
- 6.
- 7. Multiview drawings FRONT RIGHT SIDE TOP “3rd angle projection” Youwalk around part to the right (US) Rotate the part to the right (Europe) Views MUST align
- 8. The Glass Box: Bertoline,Engineering Graphics
- 9. Alignment & Orientationare preserved… Bertoline, Engineering Graphics
- 10. Six Principle views:obey layout
- 11. Basic lines (the“alphabet of lines”) Object line Hidden line Center line Dimension line
- 12.
- 13.
- 14. Interpreting Center Lines EnoughInfo? Enough Info?
- 15.
- 16. OR THIS Centerlines implysymmetry, NOT revolution per se
- 17. HERE, ONLY 2VIEWS NEEDED (Correct drawing)
- 18.
- 19.
- 20.
- 21.
- 22.
- 23.
- 24. Working with personsitting next to you copy this and draw the TOP VIEW
- 25. Working with personsitting next to you copy this and draw the TOP VIEW Possible Geometries
- 26. Working with personsitting next to you, sketch the Section View
- 27.
- 28. Working with personsitting next to you, Find the MISTAKES Wrong Wrong
- 29. Working with personsitting next to you, sketch the Section View
- 30.
- 31. DIMENSIONING 1. SHAPE 2. SIZE 3.MATERIAL 4. TOLERANCE AND FINISH
- 32. Dimensioning 5 3 5 3 • Conventions existfor choice and placement • Not too many and not too few • Never should measure off drawing with a ruler
- 33.
- 34. Dimensioning rules: …find themistakes. 3 5 5 3 5 3 5 2
- 35. Dimensioning guidelines 3 5 5 3 5 3 5 2 1. Don’toverdefine or underdefine the object. [MOST IMPORTANT] 2. Dimension to the visible contour or shape of the feature / Don’t dimension to hidden lines. 4. Don’t dimension to object lines (model edges), use extension lines. 5. Don’t overlap a dimension and the model. Place dimensions away from the model’s surface. 6. Don’t cross extension lines if possible. 7. Group dimensions when possible unless it become difficult to read. 8. Place dimensions on the side of the view were adjacent views exist (for easy referencing).
- 36. Design Detail ½” thickaluminum block Which is more expensive: A or B and why? 4.0 4.1 A B 6.0 6.0
- 37.
- 38. Dimensioning Choices &Design Intent 6 2 2 6 6 4 2 6 A B If change width of block to 8, what happens to the hole location?
- 39. Placement conventions 2.00 3.00 small gap lettersabout 1/8" tall dimension line extension line dimension arrow touches a little extended about 3/8" from part about 1/4" between dimensions 6.2
- 40. Lettering: 1 or2 directions only .5 0 .5 0 .5 0 .5 0 1 .0 0 .5 0 .5 0 OK OK NO
- 41. Extension Lines 1.000 1.000 2.007 2.000 no gaps .375.500 no break in line
- 42. All on oneside YES NO .913 2.739 .907 .913 .907 2.739
- 43. Dimensioning Rounds 0.25 R 0.125 0.75 Placedimension on view that shows the circle Show diameter rather than radius
- 45.
- 46. Tolerances • Matter becauseparts cannot be made to an exact dimension • Must specify dimension tolerance so that every part A fits every part B • Higher tolerance = higher cost • A ½ inch hole made on an ordinary drill press gives you a hole in the range 0.496 to 0.504 (+/- 0.004). For higher precision, drill undersize and use a reamer…but it will cost you more and take longer to fabricate.
- 47. ½ inch drillbit: +/- .0040 ½ inch reamer: +.0003, -.0000
- 48. LEGOS ! • Youcan combine six 8-stud bricks of the same color 102,981,500 different ways • 91% of all households with children in Denmark own LEGO products • During the period 1949-1990, 110,000,000,000 (110 billion) LEGO elements were molded • Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group. • Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret. • Dimension tolerance of mold is 0.005 mm (0.0002 inch)! 9.6 1.7 8 D 5 ABS plastic
- 49. Representing tolerances 3.000 1.000 3.005 2.995 1.005 .995 3.000 ±.005 1.000±.005 3.000 +.005 -.005 1.000 +.005 -.005
- 50. Tolerance stack-up 3.0 ±.05 5 high stack ? 14.75 15.25 What is min and max height of stack?
- 51. Tolerance Stacking What’s thetolerance (+/-) on dimension x? Ans: +/- 0.3
- 52. Chain or BaselineDimensioning? … You decide 1.0 ±.1 1.0 ±.1 2.0 ±.1 1.0 ±.1 3.0 ±.1 4.0 ±.1
- 53. Chain or BaselineDimensioning 1.0 ±.1 1.0 ±.1 2.0 ±.1 1.0 ±.1 3.0 ±.1 4.0 ±.1
- 54. Holes and shafts .626 .625 .623 .622 hole shaft .626 .625 .623 .622 1.Will all shafts fit into all holes? 2. What is maximum clearance?
- 55. ANSI standards forshaft & holes .626 .625 .623 .622 Clearance Shaft smaller than hole for all shafts and holes Interference Shaft larger than hole for all shafts and holes Transition Smallest shaft fits in largest hole Running/Sliding RC1 (fit together, no play) to RC9 (fit loosely) Force/shrink FN1 (light drive and pressure) to FN5 (high stresses and pressures) …and others Like Locational, etc. Basic hole Use nominal size of hole as starting point Basic shaft Use nominal size of shaft as starting point
- 56.
- 57. “Basic Hole” TolerancingExample 1.0000 + .0012 - .0000 1.0000 - .0008 - .0016 Drawing shows 1 in. nominal, ANSI RC4 clearance fit “Basic Hole” means smallest possible hole = nominal, then size shaft for clearance RC4 clearance = [0.0008, 0.0028] = [smallest hole-largest shaft, largest hole - smallest shaft]
- 58. Title block informationfor tolerance ALL DIMENSIONS IN INCHES HOLD ALL DIMENSIONS TO ± 0.010 UNLESS SPECIFIED Dimension Tolerance X.X ± 0.1 X.XX ± 0.05 X.XXX ± 0.001
- 59. Design Detail Bent aluminumsheet, 1/16” thick A or B: Which is more expensive and why? A B 4.0 + - 0.003 0.030 {
- 60. 1.00 ±.05 1.000 ±.005 1.0000±.00005 1.00 ±.075 $ $ $$ $$$$ Tolerance vs. Cost
- 61.
- 62.
- 63. Traditional tolerancing isambiguous 3.000 ±.005 1.000 ±.005 ? ?
- 64. Ambiguity… .25 ± .01 .25± .01 + + Square deviation Circular deviation
- 65. Geometric Dimensioning andTolerancing .25 .125 +/- .002 .01 • Ideal position of hole. .25, is marked with box and no +/- notation. • Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01
- 66. Geometric Dimensioning andTolerancing .25
- 67. GD&T Resources ME2011 website: https:// sites.google.com/a/umn.edu /me2011/resources •Efunda tutorial: http ://www.efunda.com/designs tandards/gdt
- 68. Threaded Fasteners What theyare and how to indicate on a drawing
- 69. Threaded Fasteners • Holes •Threads • Threaded fasteners
- 70. Holes DEPTH 0.75 REF 19 DRILL– 0.75 DEEP or O .166 . 75 Pix from www.mcmaster.com unless noted
- 71. Thru holes 19 DRILL– THRU or O .166
- 72.
- 73. Threaded Fasteners (screws,bolts) • Specify diameter, thread, length, head 1/4-20 x 1, RHMS ROUND HEAD MACHINE SCREW 1" LONG 20 THREADS PER INCH 1/4" DIA
- 74. Common screw threadsizes Unified Thread Standard •2-56 •4-40 •6-32 •8-32 •10-24 •1/4-20 •3/8-16 •1/2-13 •5/8-11 •3/4-10 DIA. = (N*.013) + .060 (inches)
- 75.
- 76. Head shapes Pan Flat Round Cap screw Sockethead cap screw (SHCS) Set screw
- 77. Driving a fastener Slotted Phillips Torx Hexcap Hex head (Allen head)
- 78.
- 79.
- 80. Name the Fastener: SocketHead Cap Screw Socket Head Cap Screw with counterbore
- 82. Socket Head Cap Screwwith counterbore Phillips Flat Head Screw with countersink
- 84.
- 85. Convention for screws “SCHEMATIC”“SIMPLIFIED”
- 86. Convention for threadedholes FRONT TOP FRONT SECTION 6-32 THRU
- 87. Blind threaded holes 1/2– 13 x 1.325 DEEP THREAD DEPTH DRILL DEPTH .4219 1.50 1/2 – 13 1.325
- 88. Countersunk holes .562 –82O CSK, 1.125 .562 1.125 x 82O
- 89. Counterbored holes 19 DRILL– 29 CBORE, 14 DEEP C-BORE DEPTH 19 29 14
- 91. Other Items forDrawings
- 92. Leaders & notes FINISHTOP SURFACE SMOOTH NOTE B
- 93. TITLE BLOCKS • Basic •Title • Name • Date • Units • Optional • Company name, sheet number, scale, tolerances, material, finish.... • Follow your company standards
- 94. MY PART W. DURFEE10/2/2014 ALL DIMENSIONS IN INCHES A basic title block
- 95. A title blockwith more information
- 96. www.classic-components.co.uk A title blockusing a company template
- 97. Production Drawings MODEL SKETCHES SKETCHES SKETCHES ASSEMBLY DETAIL DETAIL DETAIL DETAIL DETAIL BOM MANUALS MFG PROCESS Manytypes of drawings can be produced from the CAD database
Editor's Notes
- #1 This set of slides is designed to be read as a graphics resource. Can take excerpts for presentations. Bring: fastener/tools examples,, big real engineering drawing, an object to spin, LEGOs for tolerance section, collection of shafts and holes for tolerancing, See Notes pages 10/2011 Add: Get sample of a real engg dwg from Toro, Tennant. Along with photos of the part. 10/2009 Add: Types of drawings (detail, assembly, exploded view assembly, BOM; see Meyer et al., Technical Graphics, Chapter 9). For required text, consider Technical Graphics, Meyer et al. See lecture notes for OSU course http://www.feh.osu.edu/materials/autumn_2008.htm 10/2007 Add: tolerance stackup; show a part w/ pin mating with a hole…and all the things that could go wrong; offset section. Add features sections. Add material on hole and threading types. Intro: Eng graphics important for meche students to know…but not intellectually demanding. Basics here, details in any eng graphics text.
- #3 To fully document a part requires all of these What are examples?
- #4 Graphics is all about how to transmit this info using the conventional language. Buck these conventions at your peril…The machinist will laugh at you and your boss will relegate you to fetching coffee CAD packages automate this. Nobody uses a T-square and pencil any more
- #5 Views must line up Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”. Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”. See Betroline for details.
- #6 Views must line up Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”. Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”. See Betroline for details.
- #7 Views must line up Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”. Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”. See Betroline for details.
- #10 Great way to get relegated to making coffee.
- #11 The “alphabet of lines” ANSI standards for these
- #12 Show internal features or holes
- #13 Long-short dashed lines showing lines of symmetry and axes of cylinders and holes
- #14 Long-short dashed lines showing lines of symmetry and axes of cylinders and holes
- #15 Be careful when interpreting center lines. Do not assume axial symmetry
- #17 If circularly symmetric, drawing should tell you. If it is circularly symmetric, only need 2 views.
- #18 AT least 8 mistakes
- #19 Top view not on top; inside circle in top view not solid Bottom view not on bottom Hidden line used instead of center line Centerline in right view does not extend beyond part; Right view not aligned correctly More views than necessary No additional info like dimensions, materials, etc.
- #20 Here’s a 3-D object that has to be represented in a set of 2-D drawings. One must be careful about the conversion.
- #21 5 mistakes
- #23 Use sections for showing complex internal shapes where hidden lines would be confusing Slice through the object (the cutting plane) Hatch cut material (exposed surfaces) <…add offset sections…>
- #24 Now draw this, How many disagree?
- #25 Now draw this, How many disagree?
- #26 How many disagree? Bring samples up to front
- #27 How many disagree? Bring samples up to front
- #28 How many disagree? Bring samples up to front
- #29 How many disagree? Bring samples up to front
- #30 For revolved sections, hole pattern symmetric (convention)
- #31 Reference: Bertoline, Chapter 4
- #32 Adds *size* to object W/ CAD, natural part of part creation. W/ traditional drafting, added later Conventions for CHOICE, PLACEMENT Leave nothing to chance. Machinist should not be taking dimensions off your dwg with a ruler
- #33 Leave nothing to chance. Do not over dimension, do not under dimension
- #34 Leave nothing to chance. Do not over dimension, do not under dimension
- #35 Leave nothing to chance. Do not over dimension, do not under dimension
- #36 B is not standard stock, way more expensive. In same vein, use standard fasteners
- #37 Browse to materials > metals > aluminum > bar/sheet stock > 6061 > .50” thick > 6” long.
- #38 If change width to 8 inches, does hole move? Think *carefully* about design intent before picking a dimensioning scheme. With CAD, wrong dimensioning scheme is a major pain to correct.
- #39 Extension and dimension lines thinner than object lines Dimensions legible but not dominate See Leuptow pp. 52-55 for conventions
- #41 No gaps when crossing object lines to dimension internal features OK to cross extension lines Pro/E automates this
- #43 Put dimension on view that shows the circle. Show diameter, unless other considerations dictate radius
- #44 Highlight holes and notes
- #45 Reference: Bertoline, Chapter 4. Strongly suggest reading this chapter. Tolerances matter because it is rare that you can sit there and custom fit parts. For modern assembly, every instance of Part A must fit into every instance of Part B or else you will have a problem assembling. It is impossible to make things to an exact dimension. All mfg processes will give you a range about the nominal dimension. The more you pay, the tighter the range. For example, the outside dimensions of a block may not matter so much (tol = 0.1), but the diameter of the hole in that block matters a lot because it receives a press fit bearing (tol = tenths) A ½ inch hole made on an ordinary drill press gives you a hole in the range 0.496 to 0.504 (+/- 0.004). For higher precision, drill undersize and use a reamer…but it will cost you more and take longer to fabricate. Moral: Go with the loosest tolerance you can.
- #47 For low tolerance, drill undersize and follow with reamer
- #48 Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group. LEGO bricks are one of the most demanding ABS applications Mold tolerance is five thousandths of a millimeter (0.005 mm) or two tenths (0.0002 in.) in English units Most molds are held to 0.001 in. (one thou) in. Lego dimensions are five times more accurate. Molds for LEGO pieces are made in a factory in Germany and two factories in Switzerland Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret. ABS resin not only offers (1) tight dimensional stability required for molding to narrow tolerances, (2) flow rate, (3) impact resistance, (4) surface appearance, (5) anti-static properties, (6) no long-term creep, (7) nonflammable, (8) non-toxic.
- #51 Microphone hot-potato
- #52 Choice of dimensions from “Design Intent” Reference or “datum” dimensioning compatible with CAM. Here, left edge is a datum. Watch out for tolerance stackup
- #53 Choice of dimensions from “Design Intent” Reference or “datum” dimensioning compatible with CAM. Here, left edge is a datum. Watch out for tolerance stackup
- #54 Will this shaft always fit in this hole? What is max/min clearance?
- #55 “How loose should it be?” Much has been worked out in past. Use it. Consult machinery handbook or drafting handbook for details
- #57 Smallest hole & largest shaft: 1.0000 – 0.9992 = 0.0008 clearance Largest hole, smallest shaft 1.0012 – 0.9984 = 0.0028 clearance
- #58 4.250 = good to +/- .001 4.25 = good to +/- .01 4.3 = good to +/- .1
- #59 A. Punch shape & holes, then bend ===> cheap Press = $100/hr, 200 parts/hr B. Bend then drill ==> expensive $0.50 per hole Work with mfg (even for prototype) to reduce cost
- #63 Can left side be .995 and right side be 1.005? Can part be .995 at edges and 1.005 in middle and thus not sit flat on a table?
- #64 Hole location defines an error *square*, but we really want to allow a *circular* deviation Solved by the “Geometric Dimensioning and Tolerancing System” that allows you to specify design intent. Based on showing nominal dimensions augmented with a notation system for showing design intent for tolerances. More?: See Chapter 6 in Lueptow
- #65 Ideal position of hole is marked with box; the “true-position dimension”; no +/- notation. Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01
- #69 Bertoline references: Holes: Fig. 4.55, Sec. 8.3, Fig. 8.32, 8.37 Threads: Sect. 9.3, Fig. 9.33, 9.34 Threaded fasteners: Sect. 9.3-9.4 Fillets, rounds, chamfers: Sect. 9.6, Fig. 9.52 Bearings: Sect 9.7.4 Gears: Sect 9.7.1, Fig. 9.58-9.60
- #79 Socket Head Cap Screws
- #80 Socket Head Cap Screws
- #92 To annotate dwg with notes useful to machinist Can also refer to a notes section at bottom of page
- #94 Basic Title Name Date Optional Company name, sheet number, scale, tolerances, material, finish.... Follow ANSI or company standards For Pro/E, what are your units?