te 136 – technical drafting chapter 10: fasteners

TE 136 – Technical DraftingTE 136 – Technical DraftingChapter 10: FastenersChapter 10: Fasteners


• Objectives:Objectives:

• Identify and describe types of fasteners.Identify and describe types of fasteners.

• Define common screw thread terms.Define common screw thread terms.

• Specify threads and fasteners on a technical drawing.Specify threads and fasteners on a technical drawing.

• Draw detailed schematic, and simplified thread representations.Draw detailed schematic, and simplified thread representations.

• Name and describe common thread series.Name and describe common thread series.

• Describe and specify classes of thread fits.Describe and specify classes of thread fits.

• Draw various types of threaded fasteners.Draw various types of threaded fasteners.


• A fastener is any kind of device or method for holding parts together.A fastener is any kind of device or method for holding parts together.

• These include:These include:– SCREWSSCREWS– NUTSNUTS– RIVETSRIVETS– BOLTSBOLTS– WELDINGWELDING– BRAZINGBRAZING– SOLDERINGSOLDERING– ADHESIVESADHESIVES– COLLARSCOLLARS– CLUTCHESCLUTCHES– KEYSKEYS


• Screw . Threaded fastener designed to be inserted through a hole in one member and into a threaded hole in a mating member.

• Bolt. Threaded fastener designed to pass through holes in mating members and to be secured by tightening a nut from the end opposite the head of the bolt.


Carriage Elevator Countersunk Plow Track Stud Stove Stove

Bolt Bolt Bolt Bolt Bolt Bolt Bolt Bolt


FLAT BUTTON FILLISTER FLAT FILLISTER ROUND HEAD SOCKETFLAT BUTTON FILLISTER FLAT FILLISTER ROUND HEAD SOCKET

MACHINE SCREWSMACHINE SCREWS


Bolt/Nut Design Philosophy•ANSI standard bolts and nuts of equal grades are designed to have the bolt fail before the threads in the nut are stripped.

•The engineer designing a machine element is responsible for determining how something should fail taking into account the safety of the operators and public. Length of engagement is an important consideration in designing machine elements with machine screws.


• Screws and screw threads.Screws and screw threads.

• This principle has been used do long, it is unsure as to whom is This principle has been used do long, it is unsure as to whom is responsible for the invention.responsible for the invention.

• Archimedes (287-212 B.C.) a Greek mathematician put a screw thread Archimedes (287-212 B.C.) a Greek mathematician put a screw thread to practical use. to practical use.

• With it, he invented a means to raise water from a well (Screw pump).With it, he invented a means to raise water from a well (Screw pump).

• Screws and fasteners have so many uses, it is essential that all drafters, Screws and fasteners have so many uses, it is essential that all drafters, engineers and mechanical designers understand and can draw the engineers and mechanical designers understand and can draw the different forms.different forms.


• The true shape of a screw thread.The true shape of a screw thread.

• Screw thread can be a helical ridge on the external or internal surface of Screw thread can be a helical ridge on the external or internal surface of a cylinder.a cylinder.

• It can also be a conical spiral on the external or internal surface of a It can also be a conical spiral on the external or internal surface of a cone or frustum of a cone.cone or frustum of a cone.

• All are basically shaped like a helix (spiral – or helical curve).All are basically shaped like a helix (spiral – or helical curve).

• Right Angle wrapped around a cylinder.Right Angle wrapped around a cylinder.

• Screw thread standards.Screw thread standards.

• Practice of interchangeable parts in manufacturing lead to the Practice of interchangeable parts in manufacturing lead to the standardization of screws, threads and fasteners.standardization of screws, threads and fasteners.

• 1864, William Sellers presented the system to the Franklin Institute in 1864, William Sellers presented the system to the Franklin Institute in Philadelphia.Philadelphia.


• England had established their standards in 1861. In 1948, Canada, England had established their standards in 1861. In 1948, Canada, Great Britain and the US agreed on a Unified Thread Standards.Great Britain and the US agreed on a Unified Thread Standards.

• Globalization of Industrial Manufacturing actually started in the 40’s…Globalization of Industrial Manufacturing actually started in the 40’s…Why?????Why?????

• WWIIWWII

• ANSI now keeps the standards along with the Federal Screw Thread ANSI now keeps the standards along with the Federal Screw Thread Specifications. Why was this federally supported?Specifications. Why was this federally supported?

• Finally in 1968 the International Standards Organization adopted the Finally in 1968 the International Standards Organization adopted the ANSI (Federal) Unified system and made the standards universal. ANSI (Federal) Unified system and made the standards universal.

• ANSI was forced at this time to apply metric conversions, as Canada ANSI was forced at this time to apply metric conversions, as Canada and Europe largely use metric components.and Europe largely use metric components.


• SCREW THREAD TERMSSCREW THREAD TERMS

• Various Screw Thread Profiles (draw):Various Screw Thread Profiles (draw):– American National UnifiedAmerican National Unified

– Sharp VSharp V

– SquareSquare

– B & S Worm ThreadB & S Worm Thread

– ACMEACME

– KnuckleKnuckle


• DardeletDardelet

• British StandardBritish Standard

• ButtressButtress


• Single ThreadSingle Thread: a single ridge in the form of a helix.: a single ridge in the form of a helix.

• Double ThreadDouble Thread: two helical ridges side by side.: two helical ridges side by side.

• Triple ThreadTriple Thread: three ridges side by side.: three ridges side by side.

• Right and Left-Hand ThreadsRight and Left-Hand Threads::

• Right handed screws in when it is turned clockwise.Right handed screws in when it is turned clockwise.

• Left handed screws in when it is turned counterclockwise.Left handed screws in when it is turned counterclockwise.


• Unified SystemUnified System

• There are several constant-pitch-thread (UN) series.There are several constant-pitch-thread (UN) series.

• 4, 6, 8, 12, 16, 20, 28 or 32 threads per inch.4, 6, 8, 12, 16, 20, 28 or 32 threads per inch.

• These offer a variety of pitch-diameter combinations that can be used These offer a variety of pitch-diameter combinations that can be used where the coarse, fine, and extra-fine series are not suitable.where the coarse, fine, and extra-fine series are not suitable.

• ANSIANSI

• Although this system has largely been replaced by the Unified System it Although this system has largely been replaced by the Unified System it is important to note that the symbols are NC, NF, NEF, 8N, 12N and is important to note that the symbols are NC, NF, NEF, 8N, 12N and 16N.16N.


• THREAD SERIES:THREAD SERIES:• Screws of the same diameter are made with different pitches (numbers Screws of the same diameter are made with different pitches (numbers

of threads per inch) for different uses.of threads per inch) for different uses.• In the Unified screw-thread system, the various combinations of In the Unified screw-thread system, the various combinations of

diameter and pitch have been grouped in diameter and pitch have been grouped in screw-thread series.screw-thread series.

• COARSE THREAD SERIES (UNC OR NC): In this series, the pitch for COARSE THREAD SERIES (UNC OR NC): In this series, the pitch for each diamter is relatively large. This series is for engineering in general.each diamter is relatively large. This series is for engineering in general.

• FINE THREAD SERIES (UNF or NF): In this series the pitch for each FINE THREAD SERIES (UNF or NF): In this series the pitch for each diameter is smaller (there are more threads per inch) than in the coarse-diameter is smaller (there are more threads per inch) than in the coarse-thread series. Automobile and aerospace industries.thread series. Automobile and aerospace industries.

• EXTRA-FINE THREAD SERIES: (EUNF OR NEF): In this series, the EXTRA-FINE THREAD SERIES: (EUNF OR NEF): In this series, the pitch is even smaller than the fine thread series.Used where thread pitch is even smaller than the fine thread series.Used where thread depth needs to be very shallow…aircraft parts and thin-walled tubes.depth needs to be very shallow…aircraft parts and thin-walled tubes.


• Constant Pitch Thread Series:Constant Pitch Thread Series:

• They offer a variety of pitch-diameter combinations that can be used They offer a variety of pitch-diameter combinations that can be used where the three standard series do not offer viable options.where the three standard series do not offer viable options.

• Constant-pitch threads are often used as a continuation of coarse, fine Constant-pitch threads are often used as a continuation of coarse, fine and extra fine.and extra fine.

• When selecting a constant pitch series it is generally practiced to select When selecting a constant pitch series it is generally practiced to select an 8-, 12 or 16- thread series.an 8-, 12 or 16- thread series.

• EIGHT THREAD SERIES: This series uses 8 threads per inch for all EIGHT THREAD SERIES: This series uses 8 threads per inch for all diameters.diameters.

• TWELVE THREAD SERIES: This series uses 12 threads per inch for all TWELVE THREAD SERIES: This series uses 12 threads per inch for all diameters.diameters.

• SIXTEEN THREAD SERIES: This series uses 16 threads per inch for all SIXTEEN THREAD SERIES: This series uses 16 threads per inch for all diameters.diameters.


• SPECIAL THREADS (UNS, UN OR NS): These are non standard, or SPECIAL THREADS (UNS, UN OR NS): These are non standard, or special, combinations of diameter and pitch.special, combinations of diameter and pitch.

• LETTER SYMBOLS:LETTER SYMBOLS:– NC – COARSE THREAD SERIESNC – COARSE THREAD SERIES– NF – FINE THREAD SERIESNF – FINE THREAD SERIES– NEF – EXTRA FINE SERIESNEF – EXTRA FINE SERIES– 8N – EIGHT THREAD SERIES8N – EIGHT THREAD SERIES– 12N – TWELVE THREAD SERIES12N – TWELVE THREAD SERIES– 16N – SIXTEEN THREAD SERIES16N – SIXTEEN THREAD SERIES

• Please Note: The symbol NS denotes special threads in the Please Note: The symbol NS denotes special threads in the American National Standards thread series.American National Standards thread series.


• CLASSES OF FITSCLASSES OF FITS

• Screw threads are also divided into screw-thread classes based on Screw threads are also divided into screw-thread classes based on tolerances (amount of play from actual size) and allowances (how tolerances (amount of play from actual size) and allowances (how loosely or tightly they fit their mating parts.)loosely or tightly they fit their mating parts.)

• The exact screw thread needed can be obtained by choosing both a The exact screw thread needed can be obtained by choosing both a series and a class. series and a class.

• In brief, the classes for Unified threads are Classes 1A, 2A, and 3A for In brief, the classes for Unified threads are Classes 1A, 2A, and 3A for external threads only and Classes 1B, 2B, and 3B for internal threads external threads only and Classes 1B, 2B, and 3B for internal threads only.only.


• CLASSES 1A and 1B: Large allowance (loose fit).CLASSES 1A and 1B: Large allowance (loose fit).

• CLASSES 2A and 2B: threads standards used for general purposes CLASSES 2A and 2B: threads standards used for general purposes (bolts, nuts, screws, and similar threaded items.(bolts, nuts, screws, and similar threaded items.

• CLASSES 3A and 3B: these are stricter standards for fit and tolerance CLASSES 3A and 3B: these are stricter standards for fit and tolerance than the others. These are used where thread size must be more exact.than the others. These are used where thread size must be more exact.

• ANSI also names two other classes: Classes 2 & 3. See appendix 1 of ANSI also names two other classes: Classes 2 & 3. See appendix 1 of ANSI B1.1 (page ANSI B1.1 (page

• Thread Specifications:Thread Specifications:

• A screw thread is specified by giving its nominal (major) A screw thread is specified by giving its nominal (major) diameter, number of threads per inch, length of thread, initial diameter, number of threads per inch, length of thread, initial letters of the series, class of fit, and external (A) or internal (B).letters of the series, class of fit, and external (A) or internal (B).


.750-10 UNC - 2A.750-10 UNC - 2A

.750 = NOMINAL DIAM..750 = NOMINAL DIAM.

-10 = # OF THREADS PER INCH-10 = # OF THREADS PER INCH

UNC = THREAD SERIESUNC = THREAD SERIES

2A = INTERNAL OR EXTERNAL2A = INTERNAL OR EXTERNAL


• EXAMPLES:EXAMPLES:

• 1.25-7UNC-1A1.25-7UNC-1A

• 1.25-INCH DIAMETER, 7 THREADS PER INCH, Unified threads, 1.25-INCH DIAMETER, 7 THREADS PER INCH, Unified threads, coarse threads, Class 1, Externalcoarse threads, Class 1, External

• .75-10UNC-2A.75-10UNC-2A

• (.75-INCH DIAMETER, 10 THREADS PER INCH, Unified threads, (.75-INCH DIAMETER, 10 THREADS PER INCH, Unified threads, coarse threads, Class 2, externalcoarse threads, Class 2, external

• Metric Threads:Metric Threads:

• Specify an ISO metric screw thread by giving its nominal size Specify an ISO metric screw thread by giving its nominal size (basic major diameter) and pitch, both expressed in millimeters. (basic major diameter) and pitch, both expressed in millimeters.


M16 x 1.5M16 x 1.5

M = ISO DESIGNATION AS METRICM = ISO DESIGNATION AS METRIC

16 = NOMINAL DIAMETER16 = NOMINAL DIAMETER

1.5 = PITCH1.5 = PITCH

• Designate a 10mm diameter, 1.25 pitch, fine-thread series as Designate a 10mm diameter, 1.25 pitch, fine-thread series as M10 x 1.25.M10 x 1.25.

• Specify a 10-mm diameter, 1.5 pitch, coarse -thread series, Specify a 10-mm diameter, 1.5 pitch, coarse -thread series, however as M10…for a coarse thread you do not give the pitch however as M10…for a coarse thread you do not give the pitch unless you also give the length of the thread (M10x1.5x.25) unless you also give the length of the thread (M10x1.5x.25)


M = ISO DESIGNATION AS METRICM = ISO DESIGNATION AS METRIC

16 = NOMINAL DIAMETER16 = NOMINAL DIAMETER

1.5 = PITCH1.5 = PITCH


• EXAMPLES:EXAMPLES:

• 1.25-7UNC-1A1.25-7UNC-1A

• 1.25-INCH DIAMETER, 7 THREADS PER INCH, Unified threads, 1.25-INCH DIAMETER, 7 THREADS PER INCH, Unified threads, coarse threads, Class 1, Externalcoarse threads, Class 1, External

• .75-10UNC-2A.75-10UNC-2A

• (.75-INCH DIAMETER, 10 THREADS PER INCH, Unified threads, (.75-INCH DIAMETER, 10 THREADS PER INCH, Unified threads, coarse threads, Class 2, externalcoarse threads, Class 2, external


• PRO DESKTOPPRO DESKTOP

• LET’S TRY THIS AGAIN!LET’S TRY THIS AGAIN!

• DETAILED REPRESENTATIONDETAILED REPRESENTATION

• Approximates the real look of threads.Approximates the real look of threads.

• For this drawing it is not necessary to draw the pitch exactly to scale.For this drawing it is not necessary to draw the pitch exactly to scale.Pro Desktop Detailed Presentation


• AUTOCADAUTOCAD

• Schematic RepresentationSchematic Representation

• Shows the threads using symbols, rather than as they really look.Shows the threads using symbols, rather than as they really look.

• For this kind of drawing leave out the V’s.For this kind of drawing leave out the V’s.– Lay off the outside diameter of the screw threads.Lay off the outside diameter of the screw threads.– Lay off the thread depth and chamfer.Lay off the thread depth and chamfer.– Draw thin crest lines at right angles to the axis.Draw thin crest lines at right angles to the axis.– Draw thick root lines parallel to the crest lines.Draw thick root lines parallel to the crest lines.

• 1-10 UNC-2A1-10 UNC-2A


• AUTOCADAUTOCAD

• Simplified RepresentationSimplified Representation

• Much like a schematic representation in that it shows the threads using Much like a schematic representation in that it shows the threads using symbols, rather than as they really look.symbols, rather than as they really look.

• However, we draw the crest and root lines as hidden lines except However, we draw the crest and root lines as hidden lines except whether either may be a visible line.whether either may be a visible line.

• For this kind of drawing leave out the V’s.For this kind of drawing leave out the V’s.– Lay off the outside diameter of the screw.Lay off the outside diameter of the screw.– Lay off the thread depth and chamfer.Lay off the thread depth and chamfer.– Draw the chamfer and a line to show the length of the thread.Draw the chamfer and a line to show the length of the thread.– Draw dashed lines for the threads.Draw dashed lines for the threads.

• AUTOCAD SIMPLIFIEDAUTOCAD SIMPLIFIED


• Other Types of Threaded FastenersOther Types of Threaded Fasteners

• HEXAGON Boltheads and Nuts (fig. 10-32)HEXAGON Boltheads and Nuts (fig. 10-32)

• Lock Nuts and Lock WashersLock Nuts and Lock Washers– Split LockSplit Lock– Internal ToothInternal Tooth– External ToothExternal Tooth– Internal-external ToothInternal-external Tooth– Countersunk ToothCountersunk Tooth

• Cap Screws: fastens two parts together by passing through a clearance Cap Screws: fastens two parts together by passing through a clearance hone in one and screwing into a tapped hole in the other.hone in one and screwing into a tapped hole in the other.

• Machine Screws are used where the fastener must have a smaller Machine Screws are used where the fastener must have a smaller diameter.diameter.


• Setscrews: used to hold two parts together in a desired position. They Setscrews: used to hold two parts together in a desired position. They do so by screwing through a threaded hole in one part and bearing do so by screwing through a threaded hole in one part and bearing (pushing) against the other.(pushing) against the other.

• Woodscrews: made of steel, brass, or aluminum. Roundhead are set Woodscrews: made of steel, brass, or aluminum. Roundhead are set with the head above the wood. Flat head are set flush. Specify them by with the head above the wood. Flat head are set flush. Specify them by number, length, style of head, and finish.number, length, style of head, and finish.

• Miscellaneous Threaded Fasteners: Screw hooks, eye hooks, lag Miscellaneous Threaded Fasteners: Screw hooks, eye hooks, lag screws, etc. are designated by diameter and overall length.screws, etc. are designated by diameter and overall length.


• NON THREADED FASTENERSNON THREADED FASTENERS

• Keys:Keys:used to secure pulleys, gears, cranks and similar parts to a shaft.used to secure pulleys, gears, cranks and similar parts to a shaft.

• Rivets: Rivets: rivets and rods of metal with a preformed head on one end. rivets and rods of metal with a preformed head on one end. They are used to fasten sheet-metal plates, structural steel shapes, They are used to fasten sheet-metal plates, structural steel shapes, boilers, tanks, and many other items permanently.boilers, tanks, and many other items permanently.


• Assignment:Assignment:• 1.25-10UNC-2A, 2/5 Inches high, Button Head.1.25-10UNC-2A, 2/5 Inches high, Button Head.• You will draw:You will draw:

– DETAILED DRAWING on PRO/DESKTOP. Provide a Drawing and Split DETAILED DRAWING on PRO/DESKTOP. Provide a Drawing and Split Screen printed on the lexmark. Drawing must be on Layout A. See example. Screen printed on the lexmark. Drawing must be on Layout A. See example. (50 points)(50 points)

– SCHEMATIC DRAWING: Using AutoCAD, Layout A, see example. (25 points)SCHEMATIC DRAWING: Using AutoCAD, Layout A, see example. (25 points)– SIMPLIFIED DRAWING: Using AutoCAD, Layout A, see example. (25 points)SIMPLIFIED DRAWING: Using AutoCAD, Layout A, see example. (25 points)– These assignments are due Monday 04/21.These assignments are due Monday 04/21.

– Advice…do AutoCAD 1st. You can work on Pro/Desktop at HOME!!!Advice…do AutoCAD 1st. You can work on Pro/Desktop at HOME!!!– Note: If you do not follow instructions and print the final products as required, Note: If you do not follow instructions and print the final products as required,

ZERO points will be awarded for this drawing.ZERO points will be awarded for this drawing.


• References:References:

• Mechanical Drawing: CAD-CommunicationsMechanical Drawing: CAD-Communications, , French, Svensen, French, Svensen, Helsel & Urbanick. 12th Edition, MgGraw-Hill, NYHelsel & Urbanick. 12th Edition, MgGraw-Hill, NY

• University of Tennessee at MartinUniversity of Tennessee at Martin, Lecture 28, Engineering 478, , Lecture 28, Engineering 478, School of EngineeringSchool of Engineering

te 136 – technical drafting chapter 10: fasteners

Documents