Threads and Fasteners...

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Chapter 5Threads and FastenersTopicsExercisesCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only1Metric Thread TablesStandard screw thread tables are available in order to look up the;Major diameterPitchTap drill size or Minor diameter

Thread tables are located in Appendix B. Copyright 2010 by K. PlantenbergRestricted use only87Threads and Fasteners5.1) FastenersCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only6Exercise 5-3Unified National thread noteCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only62Exercise 5-4Metric thread note componentsCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only85Exercise 5-5Metric thread tablesCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only88FastenersFasteners include:bolts and nuts (threaded)set screws (threaded)washers keyspins Fasteners are not a permanent means of assembly such as welding or adhesives.

Copyright 2010 by K. PlantenbergRestricted use only7FastenersFasteners and threaded features must be specified on your engineering drawing. Threaded features: Threads are specified in a thread note.General Fasteners: Purchasing information must be given to allow the fastener to be ordered correctly.Copyright 2010 by K. PlantenbergRestricted use only8Threads and Fasteners5.7) Metric ThreadsCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only72Threads and Fasteners5.8) Drawing BoltsCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only94Threads and Fasteners5.9) Bolt and Screw ClearancesCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only96Thread DefinitionsExternal Thread:

An external thread is cut using a die or a lathe.

Copyright 2010 by K. PlantenbergRestricted use only12Thread DefinitionsInternal Thread: Internal threads are on the inside of a member.

An internal thread is cut using a tap.

Copyright 2010 by K. PlantenbergRestricted use only13Thread DefinitionsMajor DIA (D): The largest diameter (For both internal and external threads).

Minor DIA (d): The smallest diameter.

Depth of thread: (D-d)/2

Pitch DIA (dP): The diameter at which a line cuts the spaces and threads equally.

Copyright 2010 by K. PlantenbergRestricted use only14Exercise 5-1Screw thread featuresCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only158

Identify the Major, Minor & Pitch diameters and the Thread Depth.Skip to next part of the exercise71234561098Copyright 2010 by K. PlantenbergRestricted use only168

Identify the Major, Minor & Pitch diameters and the Thread Depth.1234Minorn109Thread DepthMajornPnCopyright 2010 by K. PlantenbergRestricted use only17

Identify the Crest, Root and Side.12CrestRoot10Side8MinornThread DepthMajornPnCopyright 2010 by K. PlantenbergRestricted use only20Thread DefinitionsScrew Axis: The longitudinal centerline.

Lead: The distance a screw thread advances axially in one turn.

Copyright 2010 by K. PlantenbergRestricted use only22

Identify the Pitch, Screw Axis and Thread Angle.AxisPitchAngleCrestRootSide8MinornThread DepthMajornPnCopyright 2010 by K. PlantenbergRestricted use only24Application Question 5-1Name an example of a left handed thread.Left peddle of a bikeCopyright 2010 by K. PlantenbergRestricted use only26Types of ThreadThere are many different types of thread forms (shape) available. The most common are;UnifiedMetric

Copyright 2010 by K. PlantenbergRestricted use only28Types of ThreadThread form choice depends on;what it will be used forlength of engagementloadetc


Types of Thread (Form)Thread NameFigureUsesUnified screw threadGeneral use.ISO metric screw threadGeneral use.

SquareIdeal thread for power transmission.Copyright 2010 by K. PlantenbergRestricted use only30

Types of Thread (Form)Thread NameFigureUsesACME Stronger than square thread.

ButtressDesigned to handle heavy forces in one direction. (Truck jack)Copyright 2010 by K. PlantenbergRestricted use only31Manufacturing ThreadsInternal Threads First a tap drill hole is cut with a twist drill.

The tap drill hole is a little bigger than the minor diameter. Why?Copyright 2010 by K. PlantenbergRestricted use only33Manufacturing ThreadsInternal ThreadsThen the threads are cut using a tap.

The tap drill hole is longer than the length of the threads. Why?Incomplete threadsCopyright 2010 by K. PlantenbergRestricted use only34Manufacturing ThreadsInternal ThreadsChamfers are sometimes cut to allow for easy engagement.

Copyright 2010 by K. PlantenbergRestricted use only35Manufacturing ThreadsExternal ThreadsYou start with a shaft the same size as the major diameter.

Copyright 2010 by K. PlantenbergRestricted use only36Manufacturing ThreadsExternal ThreadsThe threads are then cut using a die or on a lathe.

Copyright 2010 by K. PlantenbergRestricted use only37Drawing Screw ThreadsThere are three methods of representing screw threads on a drawing. DetailedSchematicSimplified

Screw thread representation present in this chapter is in accordance with the ASME Y14.6-2001 standard. Copyright 2010 by K. PlantenbergRestricted use only39Detailed RepresentationA detailed representation is a close approximation of the appearance of an actual screw thread.

Copyright 2010 by K. PlantenbergRestricted use only40Detailed RepresentationPros and Cons?

Pro: Looks good and clearly represents a thread.Con: Takes a long time to draw.Copyright 2010 by K. PlantenbergRestricted use only41Schematic RepresentationThe schematic representation uses staggered lines to represent the thread roots and crests.

Copyright 2010 by K. PlantenbergRestricted use only42Schematic RepresentationPros and Cons?

Pro: Nearly as effective as the detailed representation and easier to draw.Con: Still takes some time to draw.Copyright 2010 by K. PlantenbergRestricted use only43Schematic RepresentationRules of use for Schematic threads Should not be used for hidden internal threads or sections of external threads.

Copyright 2010 by K. PlantenbergRestricted use only44Simplified RepresentationThe simplified representation uses visible and hidden lines to represent the major and minor diameters.

Copyright 2010 by K. PlantenbergRestricted use only45Simplified RepresentationPros and Cons?

Pro: Simple and fast to draw.Con: Doesnt look like a thread.Copyright 2010 by K. PlantenbergRestricted use only46Simplified Internal Threads

Copyright 2010 by K. PlantenbergRestricted use only47Simplified Internal Threads

Copyright 2010 by K. PlantenbergRestricted use only48Drawing Screw ThreadsThread tables in the appendix can be used to look up value for the;PitchMinor diameterTap drill diameter

If screw thread tables are not available, the minor diameter can be approximated as 75% of the major diameter. Copyright 2010 by K. PlantenbergRestricted use only49Unified Threads (inch)After drawing a thread, we need to identify the size and thread form in a thread note.

Thread NoteCopyright 2010 by K. PlantenbergRestricted use only51Unified Thread Note Components

Copyright 2010 by K. PlantenbergRestricted use only52Unified Threads (inch)Major Diameter: The largest diameter.Threads per inch: Number of threads per inch for a particular diameter. Equal to one over the pitch (1/P).

Copyright 2010 by K. PlantenbergRestricted use only53Unified Threads (inch)Thread Form and Series: The shape of the thread cut. UNC = Unified National coarse. For general use.UNF = Unified National fine. Used when high degree of tightness is required.UNEF = Unified National extra fine. Used when length of engagement is limited (Example: Sheet metal). Copyright 2010 by K. PlantenbergRestricted use only54Unified Threads (inch)Thread Class: Closeness of fit between the two mating threaded parts. 1 = Generous tolerance. For rapid assembly and disassembly.2 = Normal production3 = High accuracy

Copyright 2010 by K. PlantenbergRestricted use only55Unified Threads (inch)External or Internal Threads A = External threadsB = Internal threads Right handed or left handed threadRH = Right handed (right handed threads are assumed if not stated.)LH = Left handed Copyright 2010 by K. PlantenbergRestricted use only56Unified Threads (inch)Depth of thread: The thread depth is given at the end of the thread note and indicates the thread depth for internal threadsThis is not the tap drill depth.

Copyright 2010 by K. PlantenbergRestricted use only57Unified Threads (inch)Thread class is assumed to be 2.Threads are assumed to be RH.

May be left off if assumptions hold.Copyright 2010 by K. PlantenbergRestricted use only58Exercise 5-2Identify the different components of the following Unified National thread note. 1/4 20 UNC 2A RH 1/420UNC2ARH.25 inch Major DIA20 threads per inch (P = 1/20 = .05)Thread form & series UN CoarseThread Class Normal ProductionExternal ThreadsRight Handed ThreadsCopyright 2010 by K. PlantenbergRestricted use only60Exercise 5-3Write the thread note for a #10 fine thread. (See Appendix B)


Copyright 2010 by K. PlantenbergRestricted use only64Exercise 5-3Write the thread note for a #10 fine thread. (See Appendix B)

10 32 UNFCopyright 2010 by K. PlantenbergRestricted use only65Exercise 5-3Write the thread note for a #10 fine thread. (See Appendix B)Is the major diameter 10 inches?

No10 32 UNFCopyright 2010 by K. PlantenbergRestricted use only66

Copyright 2010 by K. PlantenbergRestricted use only67Exercise 5-3Write the thread note for a #10 fine thread. (See Appendix B)Is the major diameter 10 inches?

0.19010 32 UNFCopyright 2010 by K. PlantenbergRestricted use only68Exercise 5-3Write the thread note for a #10 fine thread. (See Appendix B)What is the minor diameter?

10 32 UNFCopyright 2010 by K. PlantenbergRestricted use only69

Copyright 2010 by K. PlantenbergRestricted use only70Exercise 5-3Write the thread note for a #10 fine thread. (See Appendix B)What is the minor diameter?

10 32 UNFD 1.0825P = 0.190 1.0825/32 = 0.156Copyright 2010 by K. PlantenbergRestricted use only71Metric ThreadsThe metric thread note can contain a pitch diameter tolerance.What is the pitch diameter? Lets see.Copyright 2010 by K. PlantenbergRestricted use only73Pitch DiameterThe pitch diameter cuts the threads at a point where the distance of the spaces equal the distance of the threads.

Copyright 2010 by K. PlantenbergRestricted use only74Metric Thread Note Components

Copyright 2010 by K. PlantenbergRestricted use only75Metric Thread Note Components

Copyright 2010 by K. PlantenbergRestricted use only76Metric ThreadsMetric Form: Placing an M before the major diameter indicates the metric thread form.

Copyright 2010 by K. PlantenbergRestricted use only77Metric ThreadsMajor Diameter: The largest diameterPitch: (P) Millimeters per thread.

Copyright 2010 by K. PlantenbergRestricted use only78Metric ThreadsTolerance Class: It describes the looseness or tightness of fit between the internal and external threads.

Number = Tolerance grade Letter = Tolerance positionCopyright 2010 by K. PlantenbergRestricted use only79Metric ThreadsTolerance Class:Tolerance Grade: Smaller numbers indicate a tighter fit. Tolerance Position: Specifies the amount of allowance. Upper case letters = internal threads Lower case letters = external threads. Copyright 2010 by K. PlantenbergRestricted use only80Metric ThreadsTolerance Class: Two classes of metric thread fits are generally used.6H/6g = General purpose 6H/5g6g = Closer fit.A tolerance class of 6H/6g is assumed if it is not specified. Copyright 2010 by K. PlantenbergRestricted use only81Metric ThreadsRight handed or Left handed thread:RH = Right handed (right handed threads are assumed if not stated.)LH = Left handed

Copyright 2010 by K. PlantenbergRestricted use only82Metric ThreadsDepth of thread: It indicates the thread depth for internal threads, not the tap drill depth.


Metric Thread NoteA tolerance class of 6H/6g is assumed.Threads are assumed to be RH.May be left off if assumptions hold.Copyright 2010 by K. PlantenbergRestricted use only84Exercise 5-4Identify the different components of the following metric thread notes.M10 x 1.5 4h6h RH M101.54h6hInt. or Ext.RHMetric Form10 mm Major DIAPitch mm/threadsPitch DIA toleranceMinor DIA toleranceExternalRight handed threadsCopyright 2010 by K. PlantenbergRestricted use only86Exercise 5-5For a n16 internal metric thread, what are the; two available pitches, the tap drill diameter,and the corresponding minor diameter for the mating external threads.


Find this page.Copyright 2010 by K. PlantenbergRestricted use only90Exercise 5-5For a n16 internal metric thread.

PitchTap drill DIAMinor DIA (External)21.51414.5

13.614.2Copyright 2010 by K. PlantenbergRestricted use only91Exercise 5-5For a n16 internal metric thread.

Which has the finer thread?Pitch = 2Pitch = 1.5

Copyright 2010 by K. PlantenbergRestricted use only92Exercise 5-5Write the thread note for a 16 mm diameter coarse thread.

M16 x 2Copyright 2010 by K. PlantenbergRestricted use only93Drawing BoltsD represents the major diameter.Nuts are drawn in a similar fashion.

Copyright 2010 by K. PlantenbergRestricted use only95Bolt and Screw ClearancesBolts and screws attach one material with a clearance hole to another material with a threaded hole.

Copyright 2010 by K. PlantenbergRestricted use only97Bolt and Screw ClearancesThe size of the clearance hole depends on;the major diameter of the fastener and the type of fit normal close loose

Copyright 2010 by K. PlantenbergRestricted use only98Table 5-2 (Normal fit clearances)Other fits may be found in Appendix B.

Copyright 2010 by K. PlantenbergRestricted use only99Bolt and Screw ClearancesSometimes bolt or screw heads need to be flush with the surface. This can be achieved by using either a counterbore or countersink depending on the fasteners head shape.

Copyright 2010 by K. PlantenbergRestricted use only100Bolt and Screw ClearancesCounterbores: Counterbores are holes designed to recess bolt or screw heads below the surface of a part.

Typically, CH = H + 1/16 (1.5 mm) and C1 = D1 + 1/8 (3 mm)

Copyright 2010 by K. PlantenbergRestricted use only101Bolt and Screw ClearancesCountersink: Countersinks are angled holes that are designed to recess screws with angled heads. Typically, C1 = D1 + 1/8 (3 mm)

Appendix B gives other counterbore, countersink and shaft clearance holes.Copyright 2010 by K. PlantenbergRestricted use only102Exercise 5-6Fastener tables and clearance holesCopyright 2010 by K. PlantenbergRestricted use onlyCopyright 2010 by K. PlantenbergRestricted use only103Exercise 5-6What is the normal fit clearance hole diameter for the following nominal bolt sizes.Nominal sizeClearance hole1/43/4

9/3213/16Copyright 2010 by K. PlantenbergRestricted use only104Exercise 5-6A 5/16 - 18 UNC Socket Head Cap Screw needs to go through a piece of metal in order to screw into a plate below. The head of the screw should be flush with the surface. Copyright 2010 by K. PlantenbergRestricted use only105Exercise 5-65/16 - 18 UNC Socket Head Cap Screw Fill in the following table. Refer to Appendix B.Head diameterHeight of headNormal clearance hole dia.CBore dia.CBore depthCopyright 2010 by K. PlantenbergRestricted use only106

D = 5/16Copyright 2010 by K. PlantenbergRestricted use only107Exercise 5-65/16 - 18 UNC Socket Head Cap Screw Fill in the following table. Refer to Appendix B.Max. Head diameterA = 1.5(5/16)=0.469Max. Height of headH = D = 5/16Normal clearance hole dia.CBore dia.CBore depthCopyright 2010 by K. PlantenbergRestricted use only108Exercise 5-65/16 - 18 UNC Socket Head Cap Screw Fill in the following table. Refer to Appendix B.Max. Head diameterA = 1.5(5/16)=.469Max. Height of headH = D = 5/16Normal clearance hole dia.CBore dia.CBore depthCopyright 2010 by K. PlantenbergRestricted use only109

Copyright 2010 by K. PlantenbergRestricted use only110Exercise 5-65/16 - 18 UNC Socket Head Cap Screw Fill in the following table. Refer to Appendix B.Max. Head diameterA = 1.5(5/16)=.469Max. Height of headH = D = 5/16Normal clearance hole dia.C = D + 1/32 = 11/32CBore dia.B = 17/32CBore depthCopyright 2010 by K. PlantenbergRestricted use only111Exercise 5-65/16 - 18 UNC Socket Head Cap Screw Fill in the following table. Refer to Appendix B.Max. Head diameterA = 1.5(5/16)=.469Max. Height of headH = D = 5/16Normal clearance hole dia.C = D + 1/32 = 11/32CBore dia.B = 17/32CBore depthCopyright 2010 by K. PlantenbergRestricted use only112Exercise 5-65/16 - 18 UNC Socket Head Cap Screw Fill in the following table. Refer to Appendix B.Max. Head diameterA = 1.5(5/16)=.469Max. Height of headH = D = 5/16Normal clearance hole dia.C = D + 1/32 = 11/32CBore dia.B = 17/32CBore depth>H (H+1/16 = 3/8)Copyright 2010 by K. PlantenbergRestricted use only113Exercise 5-6An M8x1.25 Flat Countersunk Head Metric Cap Screw needs to go through a piece of metal in order to screw into a plate below. The clearance hole needs to be close and the head needs to be flush with the surface. What should the countersink diameter and clearance hole diameter be?Copyright 2010 by K. PlantenbergRestricted use only114Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.Head dia.CSink dia.Close clearance hole dia.Copyright 2010 by K. PlantenbergRestricted use only115Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.CSink dia.Close clearance hole dia.Copyright 2010 by K. PlantenbergRestricted use only116Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.CSink dia.Close clearance hole dia.Copyright 2010 by K. PlantenbergRestricted use only117

Copyright 2010 by K. PlantenbergRestricted use only118Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.A = 17.92CSink dia.Close clearance hole dia.Copyright 2010 by K. PlantenbergRestricted use only119Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.A = 17.92CSink dia.Close clearance hole dia.Copyright 2010 by K. PlantenbergRestricted use only120

Copyright 2010 by K. PlantenbergRestricted use only121Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.A = 17.92CSink dia.Y = 17.92Close clearance hole dia.Or, Y = A + 3 = 20Copyright 2010 by K. PlantenbergRestricted use only122Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.A = 17.92CSink dia.Y = 17.92Close clearance hole dia.Or, Y = A + 3 = 20Copyright 2010 by K. PlantenbergRestricted use only123

Copyright 2010 by K. PlantenbergRestricted use only124Exercise 5-6M8x1.25 Flat Countersunk Head Metric Cap ScrewMajor dia.8Head dia.A = 17.92CSink dia.Y = 17.92Close clearance hole dia.8.4Or, Y = A + 3 = 20Copyright 2010 by K. PlantenbergRestricted use only125

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