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INTRODUCTION: The technology of sheet metal work has wide application in the field of manufacturing articles from sheet metal. Such articles are often found cheap, lighter in weight and at many places they can easily replace castings (or) . In sheet metal work the knowledge of geometry, mensuration and properties of metal are most essential. Nearly all patterns came from the development of the surfaces of few geometrical models such as cylinder, prism, cone and pyramid.

IMPORTANCE: The articles which are found less expensive, lighter in weight and at many places they easily replace the use of castings or forgings. Nearly all the patterns of castings came from the development of the surfaces of few geometrical models such as cylinder, prism, cone and pyramid.

APPLICATIONS: Sheet metal components / products are used in aircrafts, heating and air conditioning systems, roof work, automobiles, trains, ships, furniture and a number of industrial and house hold appliances like hoppers, canister, guards, pipes, elbows, boxes and funnels, pans, buckets etc.

METALS USED: In sheet metal work Galvanized iron, black iron, , aluminium, stainless , and plate are commonly used. Sheet metal work is done from 16 gauge down to 30 gauge. The material being used in this shop is Galvanised iron of 28 gauge. The table below gives the gauge number and British standard wire gauge (SWG)

S.No Gauge No S W G mm 1 16 1.63 2 18 1.22 3 20 0.92 4 22 0.70 5 24 0.56 6 26 0.45 7 28 0.38 8 30 0.32

GALVANISED IRON: It is soft steel coated with molten with the help of electrolysis process. The zinc coating resist rust, improves the appearance of the metal, and permits it to be soldered with great ease.

SOLDERING: It is the process of joining two or more pieces by means of an having lower than the metal being joined. It requires iron, to heat the copper bit of , a and a .

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FLUX: A flux is a substance applied to a metal to make solder readily to the surface. It is necessary because 1. To clean the surface of during heating 2. To break down the surface tension of the solder to enable solder to flow 3. To prevent the formation of fresh oxide

SOLDER: Generally and tin alloys are used in various compositions depending upon the use of the joint. Composition of the some of the is listed below. a) Soft solder - lead 37% and tin 63% b) Medium solder - lead and tin 50% c) Electrician solder - lead 58% and tin 42% d) Plumber solder - lead 70% and tin 30% The above-mentioned alloys having a melting point between 1500 C and 4000 C. soldering is divided into two classes namely soft and hard soldering. Soft soldering is extensively used in sheet metal work for joining parts, that are not expose to the action of high temperature and excessive loads or forces. It has a melting point of approximately 1900.

The usual steps in soldering forces are: clean the metal, apply flux and then apply the solder, heat and if necessary clean the joint.

SHEET METAL JOINTS:

SEAMS: A seam is a joint made by fastening two edges together, are self secured joints.

1. Lap seam: it is the simplest type of seam in which one edge over laps the other edge and is soldered. 2. Grooved seam: it is made by hooking two folded edges together and then locking by groover. 3. Single seam: it is used to join bottoms to the bodies of vertical containers of various shapes. 4. Double seam: This seam is actually a single seam which is bent up against the body of the container. 5. Dovetail seam: it consists of a series of narrow strips of metal which are formed by slitting the end of a cylindrical or object. The narrow strips are bent in such a manner that they form a permanent joint. 6. Flanged or burred bottom seam: it is used to join the bottom of a container to its body. The flange on cylindrical jobs is often referred to as a burr, and the process of making a narrow flange is known as burring.

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3 SHEET METAL : The various operations such as cutting, , bending, folding etc. are performed by these tools. 1. Marking and measuring tools a) Steel rule b) Scriber c) Divider d) Try square 2. Cutting tools a) Straight snip b) Curved snip 3. Striking tools a) Mallet 4. Supporting tools a) Bench stake b) Beak horn stake c) Bevel edge square stake d) Funnel stake e) stake f) Hatchet stake 5. Miscellaneous tools. a) Nose b) Soldering iron 1. MARKING AND MEASURING TOOLS

STEEL RULE: It is stiff, straight steel strip having all the faces machined true. On one of the flat faces, graduations are marked in inches and centimeters. The least count is 1mm.It is used to set out dimensions.

TRY SQUARE: Try square is used for making and testing angles of 90degree. It consists of a steel blade, riveted into a hard wood stock which has a protective plate on the

4 working surface. Another type is the all-metal square, with steel blade and stock. Sizes vary from 150 to 300mm,according to the length of the blade.

SCRIBER: A scriber is a slender steel , used to scribe or mark lines on metal work pieces.

DIVIDER: It has two straight legs sharpened at one end, hinged at other end. This is used for marking circles, arcs, laying out perpendicular lines, bisecting lines, etc.

2. CUTTING TOOLS: Cutting edge

STRAIGHT SNIP: They have straight jaws and used for straight line cutting.

CURVED SNIP: They have curved blades for making circular cuts.

3. STRIKNG TOOLS: Straight Bent

MALLET: It is wooden-headed hammer of round or rectangular cross section. The striking face is made flat to the work. A mallet is used to give light blows to the Sheet metal in bending, finishing, cutting tools having wooden handle such as chisels.

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BENCH STAKE: It consists of an right angled mild steel piece fitted on the bench, used for bending at right angles.

BEAK HORN STAKE: It has a round tapered horn at one end and a square tapered horn on the opposite side. The round tapered end used for bending of sheet metal into cylinders and conical shapes etc. The squared end of stake is used for bending and truing straight-sided work.

BEVEL EDGE SQUARE STAKE:

Used to form corners and edges.

FUNNEL STAKE: It has tapered round working face. It is used for shaping conical.

PIPE STAKE: Used for hollow objects.

HATCHET STAKE: It is used to make straight, sharp bends and for folding and bending edges.

5. MISCELLANEOUS TOOLS:

NOSE PLIER: It is made of tool steel, it is having serrations for gripping purpose, used for holding and bending of sheet metal.

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b. Round nose plier a. Flat nose plier

SOLDERING IRON:

It consists of a forged piece of copper fastened to iron rod with a wooden handle on one end. It is used to join two pieces of metal by means of an alloy of tin and lead.

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