Thread Fastener

Threaded FastenersChapter 11

TOPICSIntroductionThread terminologyThread drawing and dimensioningThreaded fastenerIntroductionFASTENING TYPE1. PermanentWelding

Gluing

RivetingFASTENING TYPE2.1 Threaded fastener - bolts - studs - screws2. Temporary2.2 Non-threaded fastener - keys - pin

keyTHREAD APPLICATION1. To hold parts together.2. To move part(s) relative to others.

Part APart BPart CTHREAD APPLICATION1. To hold parts together.2. To move part(s) relative to others.

Wood working vise

Palm fruit pressing machineThread TerminologyExternal (male)threadInternal (female)threadTHREAD TERMINOLOGYA thread cut on the outside ofa cylindrical body.A thread cut on the inside ofa cylindrical body.

Internal threadExternal threadRight-handthreadThread that will assemble whenturned clockwise.Left-handthreadThread that will assemble whenturned counter-clockwise.

THREAD TERMINOLOGY

Turnbuckle use RH and LH thread at each end to double displacement.CrestRootThread angleTHREAD TERMINOLOGYThe peak edge of a thread.The bottom of the thread cut intoa cylindrical body.The angle between threads faces.Internal ThreadExternal ThreadCrestRootThread angleCrestRootMajor diameterThe largest diameter onan internal or external thread.Minor diameterThe smallest diameter onan internal or external thread.Internal ThreadExternal ThreadMinor dia.Major dia.THREAD TERMINOLOGYMinor dia.Major dia.PitchThe distance between crests ofthreads.LeadThe distance a screw will advance when turned 360o.THREAD TERMINOLOGYInternal ThreadExternal ThreadPitchPitchForm is the profile shape of thethread.Thread FormTHREAD TERMINOLOGY

Example :knuckle thread formEXTERNAL THREAD CUTTING

ToolsOperation Threading Die Die stock

Twist drill

Tools Tap Tap wrenchOperation

INTERNAL THREAD CUTTINGCOMPARISON OF THREAD CUTTINGExternal ThreadInternal ThreadMajor Dia.Minor Dia.

Thread Drawing1. Detailed representation2. Schematic representation3. Simplified representationTHREAD REPRESENTATION

External threadInternal threadDETAILED REPRESENTATION60oPitchUse slanting lines to represent crest and root.Roots and crest are drawn in sharp Vs.

Thread runout

SCHEMATIC REPRESENTATIONExternal threadPitchCrest (thin line)Root (thick line)Use alternate long and short lines for representingcrests and roots of the thread, respectively.

Internal threadSIMPLIFIED REPRESENTATIONExternal threadInternal threadUse thick continuous lines for representing crestand thin continuous lines for representing root ofthe thread, respectively.Pitch/2RootCrestThread runoutSIMPLIFIED REPRESENTATIONExternal threadInternal threadSectional viewUse thick continuous lines for representing crestand thin continuous lines for representing root ofthe thread, respectively.ISO (METRIC) THREADExternalthreadInternalthreadCenter of thread assembly60oPitch, PP/4P/8Thread assemble occurs if and only if both (internal & external)thread have an equal nominal size (or diameter) and pitch.NominalsizeMajor diameterPitchMinor diameterTap drill sizeM66.001.004.925.00M88.001.256.656.75M1010.001.508.388.50M1212.001.7510.1110.00METRIC COARSE THREADMinor diameter = Major diameter PitchMinor diameter Tap drill size[Table 9.1]Metric threadIn thread drawing, the following relationship is used.NominalsizeMajor diameterPitchMinor diameterTap drill sizeM88.000.757.1887.251.006.9177.00M1010.000.759.1889.251.008.9179.001.258.6478.75METRIC FINE THREAD[Table 9.2]Minor diameter = Major diameter PitchMinor diameter Tap drill sizeIn thread drawing, the following relationship is used.Thread LengthDRAWING STEPS OFEXTERNAL THREADStartingpositionDrawthreadaxisMajor dia.Minor dia.Draw45o ChamferDraw line making30o with thread axisDraw a circle thatrepresents a crest.Draw an arc thatrepresents a root.Internal Thread1. Through threaded holeDRAWING STEPS OFTHREADED HOLEDrawthreadaxisMajor dia.Minor dia.Draw a rootDraw a crestSectional viewDraw a circle thatrepresents a crest.Draw an arc thatrepresents a root.rootcrestSection lines are drawn into the crest of a thread.Minor dia.DRAWING STEPS OFTHREADED HOLE2. Blinded threaded holeDrawthreadaxisMajor dia.Hole depthThread depthDraw a circle thatrepresents a crest.Draw an arc thatrepresents a root.DRAWING STEPS OFTHREADED HOLE2. Blinded threaded holeSectional viewDIMENSIONING EXTERNAL THREADM101.5 1.0 Fine threadCoarse threadxxThreadlengthUse local note to specify :- thread form, nominal size, pitch (if it is a fine thread)Use typical method to specify :- thread length.3. Thread form4. Nominal size5. Pitch1. Tap drill size2. Drill depth6. Thread depth8.50 Drill, 20 Deep,M10 Tapped, 15 DeepDIMENSIONING THREADED HOLEUse local note tospecify

Threaded FastenerBOLT : TerminologyBolt is a threaded cylinder with a head. Hexagonal headbolt and nutHeadthicknessThread lengthLengthWidth across flatDimensions of bolts head arelisted in table 9.4.

DrawboltaxisDraw anend viewof the headBStartingpositionHDraw abolt headB/2B/230oLengthThread LengthMajor fDraw body of a boltBOLT : Drawing stepsM12, Bolt length 70 mm, Thread 40 mmNUT : Drawing stepsDraw an end viewof the nutBHB/2B/2Dimensions of the nut are given in Table 9.14.Dash lines representa threaded hole areomitted for clarity.1. Insert a bolt intoa clearance hole2. Insert a washer.3. Screw a nut.BOLT : ApplicationLet s think together What do you think about the following suggestions for design improvement?(B) Use shorter bolt with the same thread length.Correct(C) Reduce the thread length.InappropriateWrong(D) Add washer or nut.(A) Nothing have to be changed.Let s think together What do you think about the following suggestions for design improvement?(B) Use a bolt of this length but has a longer thread length.(C) Use a longer bolt with the same thread length.(D) Add washer.(A) Nothing have to be changed.CorrectInappropriateWrongLet s think together What do you think about the following suggestions for design improvement ?(B) Use a bolt of this length but has a shorter thread length.(C) Use a longer bolt with the same thread length.(D) Add washer.(A) Nothing have to be changed.CorrectInappropriateWrongLet s think together What do you think about the following suggestions for design improvement?(A) Use a bolt of this length but has a shorter thread length.(B) Use a longer bolt with the same thread length.(C) Use a longer bolt by increasing a thread length(D) Remove washer.CorrectInappropriateWrongLet s think together What do you think about the following suggestions for design improvement ?(A) Increase the bolt diameter.(B) Use washer with larger outside diameter.(C) Reduce the hole diameter.(D) Add washer at bolt head.CorrectInappropriateWrongLet s think together What do you think about the following suggestions for design improvement ?(B) Use a bolt with shorter thread length.(C) Add washer.(D) Increase drill and thread depths.(A) Nothing have to be changed.CorrectInappropriateWrongLet s think together What do you think about the following suggestions for design improvement ?(A) Nothing have to be changed.(B) Use a bolt with slightly longer thread length.CorrectInappropriateWrongStud is a headless bolt, threaded at both ends.STUD : TerminologyThread lengthLengthThread length

DrawingrepresentationMajor fSTUD : Drawing stepsDrawstudaxisMinor fStartingpositionStud LengthThread LengthThread LengthDraw45o ChamferDraw45o ChamferDraw line making30o with axisSTUD : Application1. Drill a hole.3. Screw a stud.4. Place the part to be fastened.5. Insert washer and fastened a nut.2. Tap a hole.Let s think together What is the mistake in the following use of stud ?Let s think together What is the mistake in the following use of stud ?Cap screw is similar to bolt, but has a longer thread than a bolt.CAP SCREW : Terminology

CAP SCREW : Counterbore holex drill,f y Cbore,z deepx drill,w deep,f y Cbore,z deepz

x drill,CSK to fyCAP SCREW : Countersink holex drill, w deep,CSK to fyyDraw 90o

SET SCREW : TerminologySet screw is a threaded cylinder used to prevent rotation or movement between parts.

SET SCREW : Application

ExerciseDraw an assembly drawing of hexagonal bolt and nut, which are used for tightening two mild steel plates with thickness 20 mm respectively.

Bolt nominal size = M30Bolt length = 120 mmBolt thickness = 0.7 dThread length = 86 mmExternal diameter of washer = 2dThickness of washer = 0.2 dNut Thickness = 0.8 d