Mechinopedia For Mechanical Engineers

Forging Presses for Smithing work are usually of the hydraulic type. The principle of a typical forging press. The water passes first from a large capacity tank to pump and then is delivered on the press with an aid of an accumulator and distributor at 200 to 300 Kg-f per cm2 (19,600 to 28,600 kN/m2). The accumulated water pressure flows into an main cylinder and presses on the top of the large piston. Since the cross-sectional area of the piston in the main material is large, the press ram is forced down upon the material to be forged which lies on the anvil with a high total into its initial position of  the action of the working fluid on the piston rods in the pull back cylinder.   To perform the motion, a relatively lower water pressure, but a large volume of water per unit of time is required to accelerate the return stroke.  In press forging, pressure or squeeze is applied to the raw material and the intensity of this pressure increases as the plastic metal r...

Steam or Air Hammers can be operated by steam or compressed air . They have no built-in compressor and, therefore, require additional facilities for supplying high pressure steam or compressed air to raise striking stroke. The principle of a steam forging is illustrated in the image below.  Both Single Acting and Double Acting steam - or - air hammer may be constructed for forging. Single acting is made for comparatively light work, while double-acting is made for heavy work. Steam Pressure at the hammer is usually 6 to 8 kg-f / cm2 (590 to 790 kN / m2) and air pressure is bit smaller than that required for steam. Rated sizes of steam forging hammers range from about 400 to 8000kg. Capacity of Forging Hammers : The ability of a hammer to deform metal depends on the energy it is able to deliver on impact. The energy from falling is used by work derived from the steam in a double-acting hammer. Steam pressures are commonly from 6 to 2 kg-f per cm2. 

In Pneumatic Hammer , the hammer has two cylinders compressor cylinder and ram cylinder . Piston of the compressor cylinder compresses air, and delivers it to the ram cylinder where it actuates the piston which is integral with ram delivering the blows to the work. The reciprocation of  a compression piston is obtained from a crank drive which is powered from a motor through a reducing gear. The air distribution device between the two cylinders consists of rotary valves with ports through which into the ram cylinder, below and above the piston, alternately. This drives the ram up and down respectively.  The size of pneumatic hammer may vary in a range from 50 to 1000kg. Hammers operate at 70 to 190 blows per minute.   

They are mechanical driven hammers with a practically constant lift and an insignificantly variable striking power. It only increases with increasing operating speed and thus has increased number of strokes per minute. The ram is driven from a rocking lever acting on an elastic rod. The rocking lever consists of a lever spring so that a elastic drive is brought drive. They are suitable for drawing out and flattening small forgings produced in the large numbers. Their disadvantage is the frequent breaking of  springs due to vibrations when in operations. Spring Hammers are built with rams weighing from 30 to 250 kg. The number of strokes varies from 200 to 40 blows per minute.  

Helve Hammers  Helve Hammers are well adapted for general engineering work where the size of the stock is changed frequently. They consist of a Horizontal wooden helve, pivoted at one end with a hammer at the other end. An adjustable eccentric between the pivot and the hammer end operates the helve. The eccentric raises the hammer which when falls strikes a blow. They are made in sizes from 5 to 200 kg. Trip Hammers  Trip Hammers have a vertically reciprocating ram that is actuated by toggle connection driven by a rotating shaft at a top of the hammer. Trip Hammers are also built in sizes from 5 to 200 kg. The stroke range of both helve and trip hammers range from about 400 a minute for small sizes to about 175 for large sizes.

Large machine parts cannot be forged by hand, since the comparatively light blow of a hand-or-sledge-hammer is unable to produce a great degree of deformation in the metal being forged. Moreover, hand forging is a lengthy process and requires repeated heating of the metal. This has led to the use of power hammers and presses in forging. Machines which work on forgings by blow are called hammers , while those working by pressure are called presses. POWER HAMMERS : All Power employ the same general principle of operation, a falling weight striking the blow, with the entire energy being absorbed by the work. Where further blows are necessary, the striking weight is raised for the succeeding blow. Some hammers employ only a gravity fall, the energy delivered on the work being the product of the weight of the hammer head and the distance of the fall. Other hammers increase the striking velocity of the hammer head by mechanical means. The part of the hammer which serves as a rigid support du...

The Forging is done by hammering the piece of metal, when it is heated to the proper temperature, on an anvil. While hammering, the heated metal is generally held with suitable tongs. Formers are held on the forging by the smith while the other end is struck with a sledge by a helper. The surfaces of formers have different shapes, and they are used to impart these shapes to the forgings. One type of former, called a fuller, having a well-rounded chisel shaped edge is used to draw out the work. Fullers are also made as anvil fittings so that the metal can be drawn out, using both top and bottom fullers. Anvil fittings of various shapes can be placed in a square hole of  the anvil. For cutting the metal, hot chisels are used. Punches and a block having a proper - sized openings are used for punching out holes. Welding can be done by shaping the surface to be welded, removing any scale or impurities from between the surfaces with a flux, and hammering the surfaces together. Hand for...

Smith Forging , also called flat-die and open-die forging, includes the broad field of forging work produced between flat faced dies and possibly supplemented by stock tooling. The final shape of the forging depends largely on the skill of the smith for size and shape.  Smith Forging, done by hand on an anvil, is employed only to shape a small number of  light forgings, chiefly in repair shops. Heavy forgings weighing up to 25,000 kg, as well as medium forgings in small batches are produced exclusively in hammers and presses. Smith forging or an open - die forging processes produce work pieces of lesser accuracy than impression or closed-die forging ; however, tooling is usually simple, relatively inexpensive and allows the production of a large variety of shapes.   There are two types of Smith Die Forging , i) Hand Forging  ii) Power Forging  

The processes of forging a metal billet between flat-dies or in a closed-impression die to obtain a part of predetermined size and shape are called smith forging or impression-die forging respectively. Depending on the equipments utilized they are further sub-divided as hand forging, hammer forging, press forging, drop hammer forging, mechanical press forging, upset or machine forging. In general, the methods of forging may, therefore, be classified as follows: 1. Smith Die Forging.       (a) Hand Forging.       (b) Power Forging .                (i) Hammer Forging.                (ii) Press Forging.  2. Impression - Die Forging.         (a) Drop Forging,         (b) Press Forging.         (c) Machine Forging.  For Production purpose it is important not only that the material can be deformed with feasible pre...

 Stages for making a link for a chain, 1) Cut the rod into four pieces of required size, three of equal lengths for 3 links and the            fourth one for the ring. 2) Heat one piece of the rod in a forge fire. 3) Place it with a round tong over the horn of an anvil and bend it by hammering with a              hand  hammer. 4.) Scarf the ends for welding . Scarfing is the method of shaping the ends of metal for                 welding. 5.) Heat the whole piece again and bend it into the shape desired and weld the scarfed ends         to from the link. 6.) Weld the second link in this manner, but the first link already made must be inserted                within it an so on until all the links are prepared.  The method of making the ring is same as before. After scarfing the ends, heat the whole p...

 The process of making a flat drill  1.) Heat one end of  the piece in a forge fire.  2.) Forge to flat taper and cut off excess metal. 3.) Heat-treat and grind the cutting edge to the shape and angle shown.  Tools Used : (1) Anvil (2), Hammer, (3) Flat Tong, (4) Flatner and (5) Foot - rule 

 1. Heat one end of the octagon steel bar.  2. Forge chamfer on head.  3. Heat other end, forge to flat taper, and then cut off excess metal.   4. Turn the chisel a quarter turn and , holding the shank horizontally, hammer the narrow           sides to make them parallel. Alternate the blows, four or five on the wider surface ,               then four or five on the narrow surface, and so on until the chisel is in the shape                    desired. 5. Heat treat and then grind. Tools used : (1) Anvil, (2) Hammer, (3) Flat Tong, (4) Flatner, and (5) Foot-rule Hardening and Tempering :  After the chisel is forged the next operation is annealing . Heat the chisel to a cherry red (a little hotter than dull red) and cool very slowly ordinarily in the air. Annealing serves to relieve , the setup by forging and to give the steel an even, clo...

 1. Heat one end of the bar for a sufficient length to make the head.  2. Jump up heated end on an anvil. 3. Flatten head by hammering against the end of the bush, placed directly over the square hole in the anvil, through which the shank will pass. 4. Swage head to size. 5. Forge chamfer on a head by a cupping a tool, using the bush as support.   Tools Used : (1) Anvil, (2) Hand Hammer, (3) Round Tong, (4) Size Plate or bush,                       (5) Flatner, (6) Swage, (7) Cupping tool, (8) Foot - rule , and (9) caliper. 

A number of operations are used to change the shape of raw material to the finished form. The typical forging operations are :  1. Upsetting. Upsetting or heading  is the process of increasing the thickness of  a bar at the expense of its length and is brought about by end pressure. The pressure may be obtained by driving the end of the bar against the anvil, by supporting on the anvil and hitting with the hammer , by placing in swage block hole and hitting with the hammer or by clamping in a vice and then hammering 2. Drawing Down.   It is the process of increasing the length of a bar at the expense of its width or thickness or both.  3. Setting Down. It is localized drawing-down or swaging operation as illustrated.                                       4. Bending Bending is an important operation in forging and is one very frequently used. This may be classified as ...

The tools and appliances used and their applications in numerous forging operations are described below : The Anvil :  The anvil forms a support for black smith's work when hammering. The body of the anvil is made of mild steel with a tool steel face welded on the body, but the beak or horn used for bending curves is not steel faced. The round hole in the anvil called pritchel hole is used for bending rods of smaller diameter, and as a die for hot punching operations. The square or hardy hole is used for holding square shanks of various fittings.  Anvils vary up to about 100 to 150 kg and should stand with the top face about 0.75 m from the floor. This height may be attained by resisting the anvil on a cast iron or wooden base. The swage block : This forge shop tool is used for mainly squaring, sizing, heading, bending and forming operations. It is 0.25 m or more wide and may be used either flat or edge wise in its stand. Hand Hammers : Two kinds of  hammers are used in...

For Forging, a metal must be heated to a temperature at which it will possess high plastic properties both at the beginning and at the end of the forging process . For instance, the temperatures to begin the forging for soft, low carbon steels is 1250*C  to 1300*C, the temperature to finish forging is 800 to 850*C. The respective temperatures for hard, high-carbon and alloy steels are 1100*C to 1150*C and 825*C to 875*C. Wrought iron is best forged at a temperature little below 1300*C . Non-ferrous alloys like brass and bronze are heated to about 600*C to 950*C, and aluminum and magnesium alloys to about 350 to 500*C  If the forging operation is finished at a lower temperature, this leads to cold hardening and cracks. With excessive heating the forgings suffer oxidation and much metal is wasted. The blanks should be heated uniformly all over and at a definite rate. The temperature of heating steel for hand forging can be estimated by heat color which is the color of the light...

The stocks that needed heating for optimizing product requirement or specifications are heated to correct the forging temperature in a smith's hearth or in a furnace located near forging operations. Gas, oil or electric- resistance furnaces or induction heating classified as open or closed hearths can be used. Gas and oil are economical, easily controlled, and mostly used as fuels. The formation of scale, due to the heating process, specially on steel creates problems in forging. A non-oxiding atmosphere should, therefore, be maintained for surface protection. New styles of gas-fired furnaces have been developed to reduce scaling to minimum. Electric heating is most modern answer to scaling, and it also heats the stock more uniformly. In some cases, coal and anthracite , charcoal containing no Sulphur and practically no ash are the chief solid fuels used in forging furnaces. However, fuels must have a calorific value of at least 1400 to 1500 large calories (5600 to 6000J). Petrole...

 The basic lattice structure of metals and their alloys seem to be a good index to their relative forgeability or work - ability. Forgeability increases with temperatures up to a point at which a second phase, e.g., from ferrite to austenite in steel , appears or if grain growth becomes excessive. Certain mechanical properties also influence forgeability. Metals, which have low ductility have reduced forgeability at higher strain rates, whereas highly ductile metals are not so strongly affected by increasing strain rates. The product designer as a wide variety of metals or alloys from which to choose the materials for forged parts. Most forging grades of ferrous or non-ferrous alloys are selected based on their inherent property levels as bar or billet materials, usually after heat treatments are performed. the forging process tends to improve some of the mechanical properties , such as impact toughness, fatigue strength, and tensile ductility, which are dependent on the gain fl...

While all the ductile materials can be forged , forgeability of the metal at the forging temperature depends upon the crystallographic structure, the melting point, yield strength, strain rate and dry friction. The metal or alloy to be forged is usually purchased as hot rolled bars or billets with round or rectangular cross sections. The following materials are ranked in order of increasing forging difficulties. 1. Aluminum alloys (GF) 2. Magnesium alloys (GF) 3. Copper Alloys (GF) 4. Carbon/low-alloy steels (GF)  5. Marten, stainless steels (SD) 6. Maraging Steels (SD) 7. Austen.. Stainless Steels (SD)  8. Nickel Alloys (SD) 9. Titanium Alloys (D) 10. Iron - base super alloys (D) 11. Cobalt-base super alloys (D) 12. Tantalum Alloys (D) 13. Tungsten Alloys (VD) 14. Beryllium (VD) Note :  The forgeability of the above mentioned materials are categorized as good (GF), somewhat difficult (SD), difficult (D) , and very difficult (VD) and has been indicated in the brackets. ...

Smithing is the act or art of working or forging metals, as iron, into any desired shape. In this process relatively small sized jobs are heated in an open fire or hearth and subsequently hammered to get the desired shape. The shop in which the work is carried out is known as the smithy or smith's shop, and the various operations are preformed by means of hand hammers or small power hammers.  Forging refers as the process of plastically deforming metals or alloys to a specific shape by a compressive force exerted by some external agency like hammer, press, rolls, or by an upsetting machine of some kind. The portion of work in which forging is done is termed the forge and the work is mainly performed by means of the heavy hammers , forging machines, and presses. Forging processes are among the most important manufacturing techniques since forged are used in the small tools, rail-road equipment, automobile, and aviation industries. 

 Hot working : 1. Hot - Working is done at a temperature above recrystallization temperature. It can therefore be regarded as a simultaneous process of deformation and recovery. 2. Hardening due to plastic deformation is completely eliminated, by recovery and recrystallization. This is true, however, only if the rate of crystallization is higher than that of deformation. 3. Mechanical properties such as elongation, reduction of area, and impact values are improved. Ultimate tensile strength, hardness, and resistance to corrosion, are not affected by hot-working if this is properly done.  4. Refinement of crystals occurs. 5. Breaks up brittle film of hard constituents, and promotes uniformity of  materials by facilitating diffusion of constituent alloys. 6. Cracks and blow holes are welded up. 7. Internal of residual stresses are not developed in the metal. Cold Working : 1. Cold working is done at a temperature below recrystallization temperature. So no appreciable recov...

Electro - Hydraulic forming is an unconventional forming process. In this process a high intensity shock wave is generated by discharging stored electrical energy across electrodes submerged in a electrolyte. A potential difference of 30KV is discharged through a wire 1 mm diameter which is immersed in water. The vaporing action of wire due to intense heat generation in turn creates high pressure shock wave. The process can be used for bulging, forging, drawing, blanking, and piercing. 

Parts of  Malleable iron , forged steel, powdered metals, aluminum and other ductile non ferrous metals are commonly finished to thickness by squeezing an operation called sizing . A special die is needed for almost every job, but each piece can be sized in a fraction of time of machining. Thus, sizing is economical wherever applicable in high production industries.   Operations like sizing have been called coining , but coining more truly involves the impression and raising of images or characters from a punch and die into a metal. The metal is made to flow, and the designs on opposite sides of a coined piece are not necessarily related as in embossing. Hard money is probably the best known product of coining.   Hobbing is a method of making molds for the plastic and die-casting industries. A punch called the hob or hub , is machined from tool steel to the shape of cavity, heated treated for the hardness, and polished . It is then passed into a blank of soft steel t...

This method is employed to set up a superficial state of surface compressive stress, causing the interior of the member to assume an opposite tensile stress. Because the fatigue generally occurs from surface cyclically loaded in tension, the useful lives of such members are frequently extended by shot peening . This method is sometimes employed to achieve an ornamental effect. Shot peening is done by blasting or hurling a rain of a small shot at high velocity against workpieces to cause slight indentations.  check out other cold working processes

Squeezing is a quick and widely used way of forming ductile metals. Of the different processes of squeezing, cold heading and rotary swaging are very common. Cold heading. Cold heading is a cold forging process, used primarily for the manufacture of bolts, screws, rivets, nails, and similar items. Materials in bar form is fed into the machine, where it is cut to length, held in a pair of jaws, and subjected to two or three blows to rough form the head. For complex shapes, or greater accuracy, the part is then repositioned in another die for final shaping or sizing. Bolt making machines combine thread rolling with cold heading to produce a complete bolt. A material to be cold headed must be ductile.  Thread rolling is a mass-production method for producing threads. It is a cold-working process, and is usually designed for automatic operation. The rolls have the thread form cut on their surface. The rolls rotate and are fed into the blank under pressure ; metal flows into a die sh...

The Principle of cold extrusion is exactly similar to that of   hot extrusion . Of the various processes of extrusion, impact extrusion is essentially a cold-extrusion method. Impact Extrusion Impact Extrusion is limited primarily for making small workpieces from the more ductile metals. The work material is placed in position into blind die and a ram punch with clearance is forced into the die, causing the metal to flow plastically around the punch. The outside diameter of the tube is the same as the diameter of  the die, and the thickness is controlled by the clearance between the punch and die. The extruding force is usually supplied by a mechanical press. Collapsible medicine tube and tooth paste tubes are made in this way.    check out other cold working processes

Cold - spinning is the operation of shaping very thin metal by pressing it against a form while it is rotating. The method is exactly similar to hot spinning except the condition of metal. In cold - spinning the metal is worked at room temperature. Equipment required for spinning comprises a lathe, forming tools, and a metal or wood former to suit the shape required. A circular blank is cut and positioned against the former by a follower . A round-nose tool is used and while the lathe rotates the blank is forced to the shape of the former. The process works the material considerably, and thinning of the metal can result. Lubricants such as soap, bees-wax, white lead, and linseed oil are used to reduce the tool friction. Cold - Spinning process is frequently used in the making of bells on musical instruments and also for light fixtures, kitchen-ware, reflectors, funnels, and large processing kettles.        check out other cold working processes

Bending is the process by which a straight length is transformed into a curved length. It is one of the most widely used forming process for changing plates (or sheets) into drums, curved channels etc. Bars, rods, wires, tubing and structural shapes as well as sheet metal are bent to many shapes in cold conditions through dies. In all metal bending, the metal stressed beyond the elastic limit is in tension on the outside and in compression on the inside of  the bend. Stretching of the metal on the outside makes the stock thinner. Bending a flat strip of metal is commonly done by roll forming. Roll forming - There are two main types of roll forming ; one uses continuous -strip material for high - production work ; the other uses sheet and plate stock. Materials used for roll forming include carbon steel, stainless steel, bronze, brass, copper, zinc, and aluminum. Among its many products are metal window and screen frame members, bicycle wheel rims, furnace, Jacked rings, trolley r...

Drawing operations involve the forcing of metal through a die by means of  a tensile force applied to the exit side of the die. Most of the plastic flow is caused by the compressive force which arises from the reaction of  the metal with the die. Usually the metal has a circular symmetry., but this is not an absolute requirement. Rods, tubes, and extrusions are often given a cold finishing operation to reduce the size, increase the strength, improve the finish, and provide better accuracy. In general, the preparatory step in cold drawing of bars, tubes that have been hot-rolled is that of  removing all traces of scale. This is best done by immersing them in a vat of dilute sulphuric acid from 15 to 30 minutes., removing, and washing in fresh water. After the scale is removed, the material is washed in lime to remove the acid. The lime, plus soap or oil, acts as a good drawing lubricant. Wire drawing - All the wire that is available is produced by cold-drawing through di...