chapter 02 thread fastener

Chapter 2Threaded Fasteners

TOPICS

Introduction

Thread terminologyThread terminology

Thread drawing and dimensioningThread drawing and dimensioning

Threaded fastenerThreaded fastener

Introduction

FASTENING TYPE1. Permanent

WeldingWelding GluingGluing RivetingRiveting

FASTENING TYPE2. Temporary

2.1 Threaded fastener- bolts - studs - screws

2.2 Non-threaded fastener- keys- pin

key

THREAD APPLICATION

1. To hold parts together.

2. To move part(s) relative to others.

P t APart A Part B

P t CPart C

THREAD APPLICATION

1. To hold parts together.

2. To move part(s) relative to others.

Wood working vise Palm fruit pressing machine

Thread Terminologygy

THREAD TERMINOLOGYExternal (male)

threadA thread cut on the outside ofa cylindrical body.thread

Internal (female)

a cylindrical body.

A thread cut on the inside ofthread a cylindrical body.

Internal threadExternal thread

THREAD TERMINOLOGY

Right-handthread

Thread that will assemble whenturned clockwisethread turned clockwise.

Left-handth d

Thread that will assemble whenthread turned counter-clockwise.

Turnbuckle use RH and LH thread at each end to double displacement.

THREAD TERMINOLOGYCrest The peak edge of a thread.

Th b tt f th th d t i tRoot

Thread angle

The bottom of the thread cut intoa cylindrical body.

The angle between threads facesThread angle The angle between threads faces.

Internal ThreadExternal ThreadThread angle

CrestRoot

CrestRoot

THREAD TERMINOLOGY

Major diameterThe largest diameter onan internal or external thread.

Minor diameterThe smallest diameter onan internal or external thread.

Internal ThreadExternal Threaddi

a.

dia.

dia.

dia.

Min

or

Maj

or

Min

or

Maj

or

THREAD TERMINOLOGYPitch

The distance between crests ofthreads.

Lead The distance a screw will advance when turned 360o.

Internal ThreadExternal Thread

PitchPitch

THREAD TERMINOLOGYForm is the profile shape of thethread.

Thread Form

Example :Example :“knuckle thread form”

EXTERNAL THREAD CUTTINGTools Operation

Threading Die

Die stock

INTERNAL THREAD CUTTING

T i t d illTools Operation

Twist drill

Tap

Tap wrenchTap wrench

COMPARISON OF THREAD CUTTINGExternal Thread Internal Thread

Minor DiaMinor Dia.

Major Dia.

Thread Drawingg

THREAD REPRESENTATION

11. . DetailedDetailed representationrepresentation

22 S h tiS h ti t tit ti22. . SchematicSchematic representationrepresentation

33 SimplifiedSimplified representationrepresentation33. . Simplified Simplified representationrepresentation

DETAILED REPRESENTATIONUse slanting lines to represent crest and root.

Roots and crest are drawn in sharp Vs.

External thread Internal threadThread runoutThread runout

60oPitch

SCHEMATIC REPRESENTATIONUse alternate long and short lines for representing

t d t f th th d ti lcrests and roots of the thread, respectively.

External thread Internal thread

Root (thick line)Pitch Crest (thin line)

Root (thick line)

SIMPLIFIED REPRESENTATIONUse thick continuous lines for representing crestand thin continuous lines for representing root ofand thin continuous lines for representing root ofthe thread, respectively.

External thread Internal threadThread runout

Pitch/2

Thread runout

Pitch/2

RootCrest

SIMPLIFIED REPRESENTATIONUse thick continuous lines for representing crestand thin continuous lines for representing root ofand thin continuous lines for representing root ofthe thread, respectively.

External thread Internal thread

Sectional view

ISO (METRIC) THREADInternalthread 60o

P/8

thread

Externalth d

P/4

threadPitch, P

Center of thread assembly

Th d bl if d l if b th (i t l & t l)Thread assembly occurs if and only if both (internal & external)thread have an equal nominal size (or diameter) and pitch.

METRIC COARSE THREADNominal Major

diameterPitch Minor

diameterTap drill size

[Table 9.1]

size diameter diameter

M6 6.00 1.00 4.92 5.00M8 8 00 1 25 6 65 6 75M8 8.00 1.25 6.65 6.75M10 10.00 1.50 8.38 8.50M12 12 00 1 75 10 11 10 00M12 12.00 1.75 10.11 10.00

Minor diameter ≈ Tap drill sizeMetric thread Minor diameter ≈ Tap drill size

In thread drawing, the following relationship is used.

Minor diameter = Major diameter – Pitch

METRIC FINE THREAD

Nominal Major diameter

Pitch Minor diameter

Tap drill size[Table 9.2]

size diameter diameter

M8 8.000.75 7.188 7.251 00 6 917 7 001.00 6.917 7.00

M10 10 000.75 9.188 9.251 00 8 917 9 00M10 10.00 1.00 8.917 9.001.25 8.647 8.75

Minor diameter ≈ Tap drill size

In thread drawing, the following relationship is used.

Minor diameter = Major diameter – Pitch

DRAWING STEPS OFEXTERNAL THREADEXTERNAL THREAD

Draw an arc that

Draw45o Chamfer

Draw line making30o with thread axis

Draw a circle thatrepresents a crest

represents a root.

Draw dia.ia.

45 Chamfer 30 with thread axisrepresents a crest.

Drawthreadaxis M

ajor

dM

inor

d

Thread Length

Startingposition

Internal ThreadDRAWING STEPS OFTHREADED HOLE

1. Through threaded hole

THREADED HOLE1. Through threaded hole

Draw a root

Draw a crestSectional view

Draw dia.ia.

Draw a root root

crestDrawthreadaxis M

ajor

dM

inor

d

Draw a circle thatrepresents a crestrepresents a crest.

Draw an arc thatrepresents a root.

Section lines are drawn into the crest of a thread.

DRAWING STEPS OFTHREADED HOLETHREADED HOLE

2. Blinded threaded hole2. Blinded threaded hole

ia.

Draw dia.

Min

or dDrawthreadaxis M

ajor

d

Thread depthDraw a circle thatrepresents a crest

Hole depth

Thread depthrepresents a crest.

Draw an arc thatrepresents a root.

DRAWING STEPS OFTHREADED HOLETHREADED HOLE

2. Blinded threaded hole2. Blinded threaded holeSectional view

DIMENSIONING EXTERNAL THREADUse local note to specify :- thread form, nominal size, pitch (if it is a fine thread)p ( )

Use typical method to specify :- thread length.

M10 ×1.5×1.0 Fine thread

Coarse thread1.0

Threadxx length

DIMENSIONING THREADED HOLE

Use local note to

1 Tap drill size8.50 Drill, 20 Deep,

specify

3 Th d f

1. Tap drill size

2. Drill depthM10 Tapped, 15 Deep

3. Thread form

4. Nominal size

5. Pitch

6. Thread depth

Threaded FastenerThreaded Fastener

BOLT : Terminology

Bolt is a threaded cylinder with a head.

Thread length

Hexagonal headHead

Length

Widthbolt and nut Headthickness

Width across flat

Dimensions of bolt’s head areDimensions of bolt s head arelisted in table 9.4.

BOLT : Drawing steps

Draw an Draw a Draw end view

of the headbolt head

30obody of a bolt

Drawbolt B/2 B/2 M

ajor

axis

H

B/2 B/2

Length

M

B

Starting

H g

Thread Length

Startingposition

NUT : Drawing steps

Dimensions of the nut are given in Table 9.14.

Draw an end viewof the nut B/2 B/2

BH

Dash lines representa threaded hole area t eaded o e a eomitted for clarity.

BOLT : Application

2. Insert a washer.

3 Screw a nut1. Insert a bolt intoa clearance hole

3. Screw a nut.

Let’ s think together…What do you think about the following suggestions fordesign improvement?

(B) U h t b lt ith th

(A) Nothing have to be changed.

(B) Use shorter bolt with thesame thread length.

(C) R d th th d l th(C) Reduce the thread length.

(D) Add washer or nut.

Correct Inappropriate Wrong


(B) Use a bolt of this length but


(B) Use a bolt of this length buthas a longer thread length.

(C) Use a longer bolt with the(C) Use a longer bolt with thesame thread length.

(D) Add washer(D) Add washer.


Let’ s think together…What do you think about the following suggestions fordesign improvement ?

(B) Use a bolt of this length but


(B) Use a bolt of this length buthas a shorter thread length.

(C) Use a longer bolt with the(C) Use a longer bolt with thesame thread length.

(D) Add washer(D) Add washer.



(A) Use a bolt of this length buthas a shorter thread length.

(B) Use a longer bolt with thesame thread length.

(C) Use a longer bolt byincreasing a thread length

(D) Remove washer.



(A) Increase the bolt diameter.

(B) Use washer with larger(B) Use washer with largeroutside diameter.

(C) R d th h l di t(C) Reduce the hole diameter.

(D) Add washer at bolt head.




(B) Use a bolt with shorterthread length.

(C) Add h(C) Add washer.

(D) Increase drill and threaddepthsdepths.




(B) Use a bolt with slightly( ) g ylonger thread length.


STUD : Terminology

Stud is a headless bolt, threaded at both ends.

Thread lengthThread length

Drawingt ti

L th

representation

Length

STUD : Drawing steps

Draw45o Chamfer

Draw45o Chamfer

Draw line making30o with axis

Maj

or Draw

studaxis M

inor

Thread Length Thread Length

Startingposition

Stud Length

STUD : Application

1. Drill a hole.

2. Tap a hole.

3. Screw a stud.

4. Place the part to be

p

4. Place the part to befastened.

5. Insert washer andfastened a nut.

Let’ s think together…What is the mistake in the following use of stud ?

CAP SCREW : TerminologyCap screw is similar to bolt, but has a longer thread than a bolt.

CAP SCREW : Counterbore hole

x drill, x drill,w deep, C’by C’bore,

z deep y C’bore,z deep

z

CAP SCREW : Countersink hole

d ill d ill dx drill,CSK to y

x drill, w deep,CSK to y

yDraw 90o

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

SET SCREW : Application

chapter 02 thread fastener

Engineering