SHEET METAL WORKING

Sheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes.

Countless everyday objects are constructed of the material.

Thicknesses can vary significantly, although extremely thin thicknesses are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate.

The thickness of the sheet metal is called its gauge. The gauge of sheet metal ranges from 30 gauge to about 8 gauge. The higher the gauge, the thinner the metal is.

There are many different metals that can be made into sheet metal, such as aluminum, brass, copper, steel, tin, nickel and titanium. For decorative uses, important sheet metals include silver, gold, and platinum.

Sheet metal has applications in car bodies, airplane wings, medical tables, roofs for building and many other things.

Sheet metal of iron and other materiales with high magnetic permeability, also known as laminated steel cores, has applications in transformers and electric machines.

and sheet metal continues to have many decorative uses, including in horse tack.

Introduction

Sheet metal is simply metal formed into thin and flat pieces.

It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of

different shapes. Countless everyday objects are constructed of the

material. Thicknesses can vary significantly, Although extremely thin thicknesses are

considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate.

Sheet metal processing The raw material for sheet metal manufacturing

processes is the output of the rolling process. sheets of metal are sold as flat, rectangular

sheets of standard size.

If the sheets are thin and very long, they may be in the form of rolls.

the first step in any sheet metal process is to cut the correct shape and sized ‘blank’ from larger sheet.

Sheet Metal Forming processes

Introduction1. Sheet metal processes involve plane

stress loadings and lower forces than bulk forming

2. Almost all sheet metal forming is considered to be secondary processing

3. The main categories of sheet metal forming are

• Shearing• Bending• Drawing

ShearingShearing is a sheet metal cutting operation

along a straight line between two cut-ting edges by means of a power shear.

Blanking and punching Blanking and punching are similar sheet metal cutting operations that involve cutting the sheet metal along a closed outline. If the part that is cut out is the desired product, the operation is called blanking and the product is called blank. If the remaining stock is the desired part, the operation is called punching. Both operations are illustrated on the example of producing a washer

BendingBending is defined as the straining of the sheet metal around a straight edge

Drawing

Drawing is a sheet-metal operation to make hollow-shaped parts from a sheet blank

Equipments

Mechanical Press –

The ram is actuated using a flywheel. Stroke motion is not uniform.

Hydraulic Press – Longer strokes than mechanical presses, and develop full force throughout the stroke. Stroke motion is of uniform speed, especially adapted to deep drawing operations

Dies and Punches

Simple- single operation with a single stroke

Compound- two operations with a single stroke

Combination- two operations at two stations

Progressive- two or more operations at two or more stations with each press stroke, creates what is called a strip development

Progressive dies & Punches

Tools and Accessories

Marking and measuring tools

Steel Rule : It is used to set out dimensions.

Try Square: Try square is used for making and testing angles of 90degree

Scriber : It used to scribe or mark lines on metal work pieces.

Divider : This is used for marking circles, arcs, laying out perpendicular lines, bisecting lines, etc

Marking and measuring tools

Cutting ToolsStraight snip - They have straight jaws and used for straight line cutting. Curved snip - They have curved blades for making circular cuts.

Straight snip

Curved snip

Striking Tools 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 and finishing.

Types of Mallets

The anvil used by the coppersmith and similar workmen is usually square, say from six. to eight inches on every side; and the smaller anvils which are called stakes, and also teests, are of progressively smaller sizes, down to half an inch square, and even less. Some of them have one edge rounded like 218; others have rounded faces as 219 and 220; a few assume the from of a rounded ridge, like fig. 222; and many have bulbs or buttons, as if turned in the lathe, as in fig. 223.

The beak-irons are also very unlike those used by the smith; they are seldom attached to the anvil, and arc often exceedingly long, as in fig. 216; some few, for more accurate purposes, are turned in the lathe to the conical form, like 221, these arc held in the vice, the jaws of which enter grooves in the shank; and mandrels four to six feet long, used for making long pipes, arc attached to the bench by long rectangular shanks and staples.

Fig. 215, the hatchet-stake, is from two to ten inches wide; it is very much used for bending the thin metals, in the same manner as the rectangular edge of the anvil is used for those which are thicker; a cold-chisel fixed in the vice forms a small hatchet-stake; 224 is the creasing-tool for making small beads and tubes; 225 is the seam-set for closing the seams prepared on the hatchet-stake; 226 is a hollow and 227 a solid punch, the cutting edge of the former meets at about the angle of fifty degrees, the latter is solid at the end for small holes; both are struck upon a thin plate of lead or solder laid upon the stake; 228 is a riveting-set or punch for the heads of rivets; and 229 is the swage-tool, a miniature of the tilt-hammer, to which a great variety of top and bottom tools, or creases, arc added, which greatly economise the labour of making different mouldings and bosses; the stop is used to retain the parallelism of the mouldings with the edge of the metal, and a similar stop is also at times applied to the hatchct-stake, 215.

Merits•High strength•Good dimensional accuracy and surface finish•Relatively low cost

Applications•Roofings•Ductings•Vehicles body buildings like 3 wheelers, 4 wheelers, ships, aircrafts etc.•Furnitures, House hold articles and Railway equipment

References

Book •Manufacturing Technology by Hajra choudry•Sheet metal working by Robert cook

Website •www.efunda.com •www.esnips.com