Mechanical Fitting Workshop

Definition of fitting shop:

“It is the process of assembling and fitting at a right place, different parts of a machine manufactured by different manufacturing process.”

It has been divided two categories:

1.  Fitting tools

2.  Fitting operations

FITTING SHOP TOOLS:

These are the helping hands while fitting and assembling a machine or a part of it. They can be hand driven or power driven. Some main fitting tools are listed below:

·      Measuring tools

·      Marking tools

·      Holding and supporting tools

·      Cutting and sawing tools

·      Striking tools

·      Drilling tools

·      Threading tools

·      Loosing and tightening tools

Measuring Tool:

These tools are used to measure the basic quantities i.e. length, mass, diameter, radius etc. They are also used to

Measure the extent or degrees of something.some basic tools in this respect are:

·     Vernier Calipers:

It is used to measure and calculate the diameter (internal or external), depth, and height, volume of sphere or cylinder. It is the most precise tool. And can calculate up to its least count. It consists of main scale and Vernier scale along with jaws for measuring internal diameter.

·     Internal calipers:

It is also known s inside calliper. It is used to measure the internal diameter. Its edges are turned outwards so that they hold workpiece. It is used to measure the diameter of a hole or width of a slot.

·      External caliper:

It is also known as inside caliper. Its jaws are turned inside to hold the workpiece from outside. It is used to measure the external diameter and also the thickness.

·     Steel ruler:

It is a simple integrated ruler of considerable long length. It is used to measure the length of workpiece .but it is not the accurate or precise way. It is used to integrate on workpiece before cutting or adjusting the length of hole for drilling. It is also used with callipers. It has two types:

·      Flexible steel ruler

·      Fixed steel ruler

Marking Tools:

Marking refers to the process of mark something on workpiece to trace back to it. Marking out is the preliminary work of providing guide lines and centre before cutting or drilling.

Marking tools are described below:-

·     Scriber:

It is used to scratching a line or marking a point on workpiece before doing any operation on it. It is made up of hard material e.g. steel and has a sharp, pointed edge.

·     Divider:

It can be used for various purposes. Its basic purpose is to make a circle of required diameter on workpiece. Along with this, it can be used to measure the diameter of that circle and for measuring length. it has pointed legs.

·     Tri-scale:

It is used for marking at 90 degree. It is also used to check whether the workpiece has cutted at right angle or not. It is made up of metal blade fit at right angle to the straight wooden handle.

Cutting Tools:

These tools help in removing or cutting the unwanted pieces of workpiece. They are used to re-size or adjust them according to required measurements.

·     Hand hacksaw:

It is used to cut the undesired part of wood or metal by using it’s to and fro motion .its blades are sharp and tethered. It is made of high carbon steel. Blade is inside the frame adjusted by nuts. Various types of blades are available in market .the teeth are generally in forward direction. It must be used in straight direction otherwise blade will get damage.

·     Files:

Files are rubbed or slide against the work piece to get desired length. It is a multi-tooth tool. They are available in number of sizes, pitches and degree of corrosiveness. It is of various types as explained below:-

·     Rough file:

It is used for large cutting and hence workpiece length can b shortened to a considerable distance. It has 20 teeth per inch.

·     Smooth file:

It is used for less cutting and work piece length cannot b shortened to a large distance. It has 50-60 teeth per inch.

·     Square file:

It is square in shape and tapered towards the tip and usually double cut on all four sides. It is used in rectangular slots or groves.

·     Round file:

It is round in shape and used in holes for enlarging them or for producing smooth curve surface in them. it is usually double cut in the larger size and single cut in the smaller size.

·     Triangular file:

It is triangular in shape with tapered towards the tip with double cut on both faces. It is used for cutting corners or angels less than 90 degrees.

·      Chisels:

These are used for chipping away the material from the work piece. These are made up of high carbon steel generally 6 inches to 8 inches long. The top is flattened and a sharp cutting edge is made on the bottom side.

Striking Tools:

These tools are used for striking or hammering or imprinting something on the work piece. They have heavy head attached to the handle.

·     Centre punch:

It is basically used before drilling. Hammering on centre punch makes a hole in the metal. Now, while drilling, the drill bit exactly touches that hole impression and makes a perfect hole. They are made of hard steel material.

·     Hammer:

Hammer is used for striking on something. It is the most easy to use tool. It consists of a hard material iron head attached to a wooden handle. The weight ranges from 0.2 to 2 kg. It is classified on the basis of head shape. It has following types:

·     Claw hammer:

If the head is round from one side but the other end is bent downward slightly, then it is claw hammer. It is also used to pull a nail out of the work piece.

·     Cross peen hammer:

If one end is round and tapered while other end is pointed, then it is cross peen hammer.

  
Drilling tool:

Tools which are used in drilling operations i.e. for making holes are:

·     Drill bit:

It used for making round holes. Drill bit can be used with different blades. It is made up of steel. It rotates at a very high speed. Drill bits are cutting tools used to create cylindrical holes, almost always of circular cross-section. Drill bits come in many sizes and have many uses. Specialized bits are also available for non-cylindrical-shaped holes.

The shank is the part of the drill bit grasped by the chuck of a drill. The cutting edges of the drill bit are at one end, and the shank is at the other end.

·     Drill chuck key:

A chuck key is a device used on a keyed chuck to match the gears on the chuck. Chuck keys are quite small, and can easily be misplaced. Thus, most manufacturers of hand power drills with keyed chucks add a key holder for the chuck key on the power cord. It is also used to loosen the bolts.

·     Counter sinking tool:

Tool for making a hole with the top part enlarged so that the head of a screw or bolt will lie flush with or below the surface. A cross-hole countersink is a cone-shaped tool with a cutting edge provided by a hole that goes through the side of the cone.

·     Reamers:

Tools which are used in reaming are called as reamers.  They are used to control the diameter of hole. They are used to improve the finishing of hole surface, they are made of high carbon steel. They can be hand reamers or machine reamers.

Threading Tool:

Making circular impressions on nuts and bolts is called

Threading. Tools which are used for this purpose are pointed having circular groves on them. Some of them are listed below:

·     Tap:

They are used for internal threading by inserting them into the hole at right angel to the face of hole. In hand tapping, three taps are used. They are inserted into hole

 

and moved clockwise and then anti-clockwise direction to fix the impression. They are made of high carbon steel.

·     Tap handle:

Hand taps are used by inserting them in handle. it is a type of tap wrench where force is applied by palm. It requires more pressure and force.

·     Die:

It is used for external threading on nuts and bolts. they are also made of high carbon steel. They are available in different pitches and can be used according to desired threads.

·     Die-handle:

Die handle is used for making external threads by human effort. Die is inserted into die-stock and then rotated by hand.

Loosing and tightening tools:

Tools used in fitting shop are:

·     Screw driver:

It is a tool used for driving screws with a flattened or cross shaped tip that fit into the head of a screw to turn it. It is available in many types and sizes.

·     Spanner:

A wrench that has a hole, projection or hook at one or both ends of the head for engaging with a corresponding device on the object that is to be turned. There are different types of spanners:

·      Open end spanner

·      Close end spanner

·      Combination spanner

Open end spanner:

It is the most common type and may have a single or double end. The head has its jaws offset by about 15 degree from the run of shaft. This makes them to use in confined space.

Close end spanner:

The most useful spanner having offset heads, allowing the spanner to connect with nuts in awkward place and too give room to your hand to move without hitting the workpiece.

Combination spanner:

Spanners having one end close while other end open is called as combination spanner.

·     Adjustable wrench:

It is also known as adjustable spanner. it is used for loosing and tightening a nut or bolt. It has the ability to open and close its mouth according to the diameter of bolt with the help of a rotating cylinder.

Others commonly used Tools:

·     Allen key:

It is a tool of hexagonal cross section head used to loosing or tightening bolts and screws that have a hexagonal socket in their head.

·     Allen bolt:

It is a bolt having external threads. It is of short size. Its speciality is that it has a hexagonal socket in its head.

·     Threads pitch gauge:

It is used to check the pitch of threads. It consists of number of grooves or leaves. On every leaf cut is

 
 Provided to fit into the thread while checking. All leaves are assembled in a holder. The material of leave is stainless steel.

·     Number punch:

A number punch is a hard metal rod with a shaped tip at one end and a smooth surface on other end, which is used for hammering on it .some numbers are embedded on one end. These are used to emboss the impression of number into a workpiece. They are most common in reverse image. This allows the end results to be immediately readable on the workpiece.

·     Nut:

A nut is a type of fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts. Nuts are graded with strength ratings compatible with their respective bolts. A wide variety of nuts exists, from household hardware versions to specialized industry-specific designs that are engineered to meet various technical standards.

·     Bolt:

A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. The most common uses of screws are to hold objects together and to position objects. A screw will always have a head, which is a specially formed section on one end of the screw that allows it to be turned, or driven.

FITTING SHOP OPERATIONS:

The various operations of fitting shop are:-

    i.            Measuring operation:

Measuring is a process in which we consider the physical features of an object. We get knowledge about its length, mass, height, internal or external diameters, depths etc. This is done with the help of measuring tools like Vernier calliper, callipers, screw gauge, ruler

etc. This is the most basic operation and the initial step of every procedure.

ii.            Marking operation:

Marking out or layout is the process of transferring a design or pattern to a workpiece, as the first step in the manufacturing process. Marking out consists of transferring the dimensions from the plan to the workpiece in preparation for the next step, machining or manufacture. After measuring form measuring tool, some marking tools are used e.g. scriber, tri-square, dividers etc, mark the desired area on workpiece.

iii.            Sawing operation:

A saw is a tool consisting of a hard blade, wire, or chain with a toothed edge. It is used to cut through relatively hard material, most often wood. The cut is made by placing the toothed edge against the material and moving it forcefully back and forth. This force may be applied by hand, by steam, water, electricity or other power source. An abrasive saw has a powered circular blade designed to cut through metal. Cutting the workpiece through this method is called sawing operation.

 

iv.            Filling Operation:

The process of making up or something putting into a hole, cavity, space or container is called filling.

v.            Punching Operation:

Punching is the process of engraving or embossing some impression (forcefully or by hammering) on any other surface. In fitting shop, it is divided into:

·      Centre punching

·      Number punching

Centre punching:

Making an impression of hole in workpiece is called centre punching. It is mainly used in drilling.

Number punching:

Engraving numbers on workpiece forcefully or by hammering is called number punching.

 

vi.            Drilling operation:

Making a hole with the help of drill bit is called drilling. Drilling is one of the most complex machining processes. The chief characteristic that distinguishes it from other machining operations is the combined cutting and extrusion of metal at the chisel edge in the centre of the drill. The high-thrust force caused by the feeding motion first extrudes metal under the chisel edge. Then it tends to shear under the action of a negative rake angle tool.

vii.            Reaming operation:

The process of enlarging the hole is called reaming. There are many different types of reamer and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press. A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing burrs. Reaming can be done on a drilling machine by using a hand reamer or using a machine reamer.

viii.            Boring Operation:

Occasionally a straight and smooth hole is needed which is too large or odd sized for drills or reamers. A boring tool can be inserted into the drilling machine and bore any size hole into which the tool holder will fit. boring is the process of enlarging a hole that has already been drilled (or cast), by means of a single-point cutting tool (or of a boring head containing several such tools), for example as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters.

ix.            Counter Boring Operation:

Counter boring is the process of enlarging the entrance of a hole with a counter bore, or other similar tool to a specified diameter and depth. Counterbores provide a square shoulder so that a cap screw or bolt head may sit flush or below a surface. Counter bores are available in a variety of sizes and styles. A hole-making operation that enlarges one end of a previously drilled hole to a certain depth. The enlarged end contains a flat interior.

x.            Counter Sinking Operation:

The cutting of a bevelled edge at the end of a hole so that the head of a screw can rest flushes with the workpiece surface. A countersink is a conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt or screw, when placed in the hole, to sit flush with or below the surface of the surrounding material.

xi.            Threading Operation:

The process of cutting a long, spiralling groove into a workpiece with a single-point tool. Threading processes are essential for the creation of fasteners. A thread is a uniform helical groove cut inside of a cylindrical workpiece, or on the outside of a tube or shaft. They are according to desired pitch. It is of two types:

·     Internal threading:

When the threads are on the inner surface of workpiece.

·     Outer threading:

When the thread are on the upper surface of workpiece.