SUBJECT : PRODUCTION TECHANOLOGY (2161909 )

Gandhinagar Institute of Technology

Active Learning assignment on:-“Thread Manufacturing ”

Prepared by:-Savsani Happy (150123119045)

Introduction Thread is ridge of uniform cross section in the form of a

helix provided on the outside or inside of a cylindrical or conical surface.

External threads are provided on bolts, screws while internal threads are on corresponding nuts or any machine members.

Functionally fasteners are threaded for holding component securely.

Thread manufacturing is a very important manufacturing activity because of huge demand of high precision fastening devices and power transmission systems.

Elements of Screw Thread

Major DiameterMinor DiameterPitch DiameterPitch Thread Depth Thread AngleCrest /RootNo. of start LeadHandForms

1) ISO Metric thread2) V-Thread3) Square thread 4) British standard Whitworth5) British Association6) American nationals7) Acme thread8) Knuckle Thread

Methods of Thread manufacture:

1. Thread cutting on Lathe2. Thread Chasing3. Die threading4. Tapping5. Thread Milling6. Thread rolling7. Thread Grinding8. Thread casting9. Thread Whirling

Thread cutting on Lathe Principle is to produce helical groove on a cylindrical or conical

surface by feeding tool longitudinally when job is rotating.

Steps :1) Selection of cutting tool 2) Mounting of cutting tool and workpiece 3) Establish relation between longitudinal movement of cutting

tool and work piece rotation.4) Thread Cutting5) Tool feeding and Thread catching

Thread Chasing: It is method of thread cutting with the help of multi point cutting

tool called thread chaser. Chaser types:

1) Hand Chaser 2) Threading tool Chaser

Hand chaser is worked manually by hand during operation with provision of suitable support.

Threading tool chaser has two useful forms as Flat type and Circular type. Both are fixed in tool holder and used for cutting thread in large scale production.

This chasers consist Cutting teeth for cutting operation and Sizing teeth for finishing operation.

Die Threading: External threads cutting on cylindrical or taper surface by

means of Solid and self opening dies is called die threading. Dies are look like nuts but it is made of Hardened Steel or HSS

with sharp cutting edges. This dies are coaxially rotate around the blank. Types of Die

1) Solid die2) Self opening die

Tapping: Tapping is Thread cutting process for producing internal threads. Multipoint cutting ( Tap ) is used like die threading and cutting

may be done manually or on machines. In machine , process is similar as manual tapping except feed

being automatic and threads will be high accurate and uniform. During machining features like fast retraction of the tool,

automatic loading or unloading, use of multiple spindles; machining rate will considerably increased.

Taps are classified as Solid taps and Collapsible taps.

Solid Taps It is one piece construction and

similar to threaded bolt with four flutes to provide cutting edges.

It is used for small diameters and worked manually. So it is also known as hand taps.

Taper tap, Plug tap and Bottoming tap are used as Solid tap.

Taper tap is tapered at starting for six threads to make entry easy.

Plug tap is also chamfered little for few threads and it is used as second tap after removing first tap.

Bottoming tap is used after second tap to cut thread up to the bottom of the hole. `

Collapsible taps It is tool which collapse inwards

automatic when thread is completed.

It permits return without unscrewing . So speed of operation is increased.

Due to machining surface finish is good .

The taps are provide with trip plate which set accordingly the length of thread to be cut.

Thread Rolling It is cold forming process used for making external threads on

cylindrical w/p. Threads are formed into blank by pressing thread rolling die

against the blank. Faster method of production Skilled labor not required , so it is economical method of thread

making. Chip less operation, no wastage of material. Threads produced by rolling have good quality and high accuracy. Thread rolling increase tensile and fatigue strength of work

material but rolling process is limited to ductile materials. Thread rolling machines:

1) Reciprocating Flat die machine.2) Cylindrical two/three die machine.

Flat die machine Two dies are used. One is

bottom die which remains stationary and another is reciprocating die.

Blank is placed on stationary die and then moving die slides over the blank. Due to such action blank roll between two dies and threads are formed.

Cylindrical die machine Cylinder die machine use two

/ three dies. Incase of two die machine as

shown in figure work blank is supported between two dies.

Incase of three die machine one die is move radial outward for let the work blank enter between die and then closes and rotate to roll threads.