Reamer and its types

Reamer:

A reamer is a rotating cutting tool generally of cylindrical shape which is used to enlarge and finish holes to accurate dimensions to previously formed hole. It is a multiple edge cutting tool having the cutting edge on its periphery.

Parts of Reamer:

A reamer consists of three mean parts:

1.     Fluted section

2.     Neck

3.     Shank

The fluted part consists of chamfer, starting taper, sizing section and back taper length. Chamfer length or bevel lead insures proper and easy entry of the reamer into the hole. The main cutting action of reamer is done by starting taper, the sizing section and to guide the reamers and also smooth or size the hole. The back taper reduces friction between reamers and the whole surface.

Types of Reamers:

There are following types of reamers:

·        Hand Reamer

·        Machine Reamer

·        Chucking Reamer

·        Fluting Reamer

·        Expanding Reamer

·        Adjustable Reamer

·        Shell Reamer

1: Hand Reamer:

These reamers are operated by hand with a tap wrench fitted on the sequence of the reamer. The work is hold in a vice. The flutes may be straight or helical. Shank is straight with a square tang for the wrench.

2: Machine Reamer;

These are similar to hand reamer, except that the shank is tapered.

3: Chucking Reamers:

These are machine reamers with shorter flutes. These may be either of the type known as rose reamers or fluted reamers. These are using for heavy roughing cuts.

4: Fluting Reamers:

There the holder are not rigid but are fluting this permits the reamer. To flow the previously made hole naturally and without restrained resulting in a better hole.

5: Expanding Reamers:

These reamers allow slight increase in their size to allow for wear to remove an extra amount of material. For this the body of the reamers is bored tapered and is slitted. A taper plug runs through the hole end is operated by a screw so that it acts as the expander.

6: Adjustable Reamers:

In these reamers separate blades are inserted in the grooves provided in the body of the reamer. The blades can be moved up or down of the reamer.

7: Tapered Reamers:

These reamers are used to finish the taper holes for cutting the taper things used to secure the collars, pulleys etc to the shaft.

8: Shell Reamers:

Solid reamers (upto about 20mm diameter or usually made of Hss) to reduce the cost of larger reamers the cutting portion is made as separate shell which are mounted on standard shanks made of lower cost steel. These reamers are however do not very rigid and accurate inserted tooth or plates in shells in further reduced the cost of reamers can tip with cemented carbides.

Moulding sand properties and its types

Moulding sand properties and its classification:

The moulding is a process of making a cavity or mould out of sand by means of a pattern. The molten metal is poured into the moulds to produce casting.

Properties of moulding sand

1: porosity or permeability

It is the property of sand which permits the steam and other gases to pass through the sand mould. The porosity of sand depends upon its grain size, grain shape, moisture and clay components are the moulding sand. If the sand is too fine, the porosity will be low.

2: Plasticity

It is that property of sand due to which it flows to all portions of the moulding box or flask. The sand must have sufficient plasticity to produce a good mould.

3: Adhesiveness

It is that properties of sand due to it adheres or cling to the sides of the moulding box.

4: Cohesiveness

It is the property of sand due to which the sand grains stick together during ramming. It is defined as the strength of the moulding sand.

5: Refractoriness

The property which enables it to resist high temperature of the molten metal without breaking down o r fusing.

Classification of Moulding sand according to their use:

1: Green sand

 The sand in its natural or moist state is called green sand. It is also called tempered sand. It is a mixture of sand with 20 to 30 percent clay, having total amount of water from 6 to 10 percent. The mould prepared with this sand is called green sand mould, which is used for small size casting of ferrous and non-ferrous metals.

2: Dry Sand

The green sand moulds when baked or dried before pouring the molten metal are called dry sand moulds. The sand of this condition is called dry sand. The dry sand moulds have greater strength, rigidity and thermal stability. These moulds used for large and heavy casting.

3: Loam Sand

A mixture of 50 percent sand grains and 50 percent clay is called loam sand. It is used for loam moulds of large grey iron casting.

4: Facing Sand

A sand which is used before pouring the molten metal, on the surface is called facing sand. It is specially prepared sand from silica sand and clay.

5: Backing or Floor Sand

A sand used to back up the facing sand and not used next to the pattern is called backing sand. The sand which have been repeatedly used may be employed for this purpose. It is also known as black sand due to its colour.

6: System Sand

A sand employed in mechanical sand preparation and handling system is called system sand. This sand has high strength, permeability and refractoriness.

7: Parting Sand

A sand employed on the faces of the pattern before the moulding is called parting sand. The parting sand consists of dried silica sand, sea sand or burnt sand.

8: Core Sand

The cores are defined as sand bodies used to form the hollow portions or cavities of desired shape and size in the casting. Thus the sand used for making these cores is called core sand. It is sometimes called oil sand. It is the silica sand mixed with linseed oil or any other oil as binder.

Lathe fixtures or turning fixtures

2: Lathe Fixtures(Turning fixtures)

The standard work holding devices or fixtures for lathe are:

·        Three and four jaw chucks

·        Collets

·        Face plate

·        Mandrels

·        Milling vice

If the job can be held easily and quickly in the above mentioned standard devices, then there is no need for special work holding devices. However many jobs particuly casting and forging, because of their shapes, cannot be conveniently held by any of the standard devices. It then becomes necessary to build a special work holding device for the job. Such a device is called lathe fixture.

A lathe fixture consists of a base , location and clamping devices. A lathe fixture can be fixed to the lathe either by holding in the chuck jaws or fixing to a face plate.

Basic Design Principles for Turning or Lathe Fixtures:

1.     To avoid vibration while revolving , the fixture should be accurately balanced.

2.     There should be no projections of the fixture which may causes injury to the operator.

3.     The fixture should be rigid and overhang should be kept minimum possible so that there is no bending action.

4.     Clamps used to fix the fixture to the lathe should be designed properly so that they don’t get loosed by centrifugal force.

5.     The fixture should be as light weight as possible since it is rotating.

6.     The fixture must be small enough so that it can be mounted and revolved without hitting the bed of the lathe.

Methods of cutting operations

Methods of Cutting operation:

1: Orthogonal Cutting Process:

Orthogonal cutting occurs when the major cutting edge of the tool is presented to the work piece perpendicular to the direction of the feed motion. Orthogonal cutting is shown in figure:

2: Oblique Cutting Process:

Oblique cutting occurs when the major edge of the cutting tool is presented to the work piece at an angle which is not perpendicular to the direction of the feed motion, its diagram show that chips removal are the continuous type.  

Forging operations and types

Forging operations:

1: Drawing:

This is the operation in which metal gets elongated with a reduction in the cross sedation area. For this, a force is to be applied in a direction perpendiaulant to the length axis.

2:Up setting:

This is applied to increase the cross seat ional area of the stock at the expanse of the length. To achieve the length of upsetting force is applied in a direction parallel to the length axis, For example forming of a bolt head.  

3:Fullering:

It a similar to material cross-section is decreased and length increased. To do this; the bottom fuller is kept in angle hole with the heated stock over the fuller .the top fuller is then kept above the stock and then with the sledge hammer, and the force is applied on the top fuller.  

                           

4:Edging:

It is a process in which the metal piece is displaced to the desired shape by striking between two dies edging is frequently as primary drop forging operation.

5:Bending:

Bending is very common forging operation. It is an operation to give a turn to metal rod or plate. This is required for those which have bends shapes.

6:Punching:

It is a process of producing holes in motel plate is placed over the hollow cylindrical die. By pressing the punch over the plate the hole is made.

7:Forged welding:                                                                                                                                                       It is a process of joining two metal pieces to increase the length. By the pressing or hammering then when they are at for ging temperature.Itis performed in forging shop and hence is called forged welding.

8:Cutting:

It is a process in which a metal rod or plate cut out into two pieces, with the help of chisel and hammer, when the metal is in red hot condition.

9:Flating and setting down:

Fullering leaves a corrugated surface on the job. Even after a job is forged into shape with a hammer, the marks of the hammer remains on the upper surface of the job. To remove hammer marks and corrugation and in order to obtain a smooth surface on the job, a flatter or set hammer is used.

 10: Swaging:

Swaging is done to reduce and finish work for desire size and shape, usually either round or hexagonal. For small jobs top and bottom swage pair is employed, where as for large work swage block can be used.

Extrusion processes

Extrusion Processes:

Extrusion is the process of confining the metal in a close cavity and then allowing it to flow from only one opening , so that the metal will take the shape of the opening. The operation is identical to the sequeezing of toothpaste out of the toothpaste tube.

By the extrusion process, it is possible to make component which have a constant cross section over any length as can be formed by the rolling process. Some typical parts can be extruded are shown:

Compexity of parts that can be obtain by extrusion is more than that of rolling, because the die required being very simple and easier to make. Also extrusion is a single pass process,unlike rolling the amount of reduction that si possible in extrusion is large. Generally brittle materials can be very easily extruded. It is also possible to produce sharp corners and different angles. It is possible to gets shapes with internal cavaties in extrusion by the use of spider die. Large diameters, thin walled , tubler products with execellent concentricity and tolerance charasitic can be produced.

Types of extrusion:

1: Direct extrusion or forward extrusion

2: Indirect extrusion or backward extrusion

Drilling Jigs

Drilling Jigs:

Drilling jigs are used to machine holes in mechanical products to obtain positional accuracy of the holes harden drill bushes or jig bushes are used to locate and guide drills and reamers etc. In relation to the work piece these guide bushes are not essential but these prove to be economical and technically desirable. The position of the jig into which the harden bushes are fitted is called bush plate. Drilling jigs are either clamped to the work piece in which holes are to be drilled or the work piece is housed and clamped in the jig body. If more than one hole is to be drilled , the drill jig is made to slide on the table to drilling machine. Such a drill jig is moved by hand into position under the drill so that the drill radially enters the bush. During the drilling operation the jig is held by hand. If the drill size is large enough to produce a high torque , either stops should be provided or the drill jig is clamped to the table of the drilling machine. A drill jig is provided with feet which rest or slide on the table of drilling machine. These feet should be outside of the cutting forces, thus providing solid support. Drilling jigs make pysible the drilling of holes at higher speed with greater accuracy and with less skilled worker. Then is possible when the holes are laid out and drill by hand. Also they produce inter changeable parts because each part drilled in a drilling jig should have the same hole pattern as every other parts.

It is clear that during the drilling operations burs will be produced. The bur produced at the short of the hole is smaller than that produced at the end of the hole. The first type is called minor burs and second type is called major burr. (when the drill makes through the material). When designing a drill jig these two types of burr should be taken into consideration since they may cause difficulty in unloading the work piece from the jig after a hole has been drilled.

Drill and its parts

Drill or Drilling operation:

Drilling is the process of cutting or originating a round hole from the solid material. There are many ways of classifying drills. The tool(drill) and not the work piece is revolved and is fed into the material along its axis.

 For example , according to material, number and types of flutes, drill size , type of shank(straight or taper) and cutting point geometry etc. However the most common type of drill is the fluted drill shown in figure.

It is made from a round bar of tool material , and has three principles parts: the point, the body and the shank. The drill is held and rotated by its shank. The point comprises the cutting elements while the body guides the drill in the operation. The body of the drill has two helical grooves called “ flutes”. The flutes from the cutting surface and also assist in removing chips out of the drilled hole. The parts of twist drill are:

1: point:

The point is the cone shaped end and it does the cutting. It consists of the following:

(A)   dead center: It is the sharp edge at the extreme tip of the drill. This should always be the exact center of the drill.

(B)   Lips: these are the cutting edges of the drill.

(C)   Heel : It is the portion of the point back from the cutting edge.

2: Shank :

It is the portion of the drill by which it is clamped in the spindle. The shank may be either straight or tapered. Straight shank drills are used with a chuck. Tapered shank drills have self-holding tapes that fit directly into the drill press spindle. On the taper shank is the another term is used which is called tang. This fits into a slot in the spindles sleeve.

3: Body :

It is the portion between the point and the shank. The body consists of the following parts:

(A) Flutes :

Two or more spiral grooves that run the length of the drill body are called flutes. The flutes do four thing.

·        Help from the cutting edge of the drill point.

·        Curl the chip tightly for easier removal.

·        From channels through which chips can escape from the hole being drilled.

·        Allow the coolant and lubricant to get down to the cutting edge.

(B) Margin

It is the narrow strip extending back the entire length of the flute. It is the full diameter of the drill.

(C) Body Clearance:

It is the part of the drill body that has been reduced in order to cut down friction between the drill and the wall of the hole.

Design principles Common to jigs and fixtures

Design principles Common to jigs and fixtures:

There are some principles which are useful to design jigs and fixtures.

1: Rigidity:

Jigs and fixtures should be sufficiently stiff to secure the preset accuracy of machining.

2: Fool proofing:

It can be defined as “ the incorporation of design feature in the jig or fixture that will make it possible to lead the work into jig and fixture, in an improper position , but will not interfere with loading and unloading the work piece.” There are many fool proofing devices , such as fooling pegs, blocks or pins which clears correctly position parts but prevent incorrectly loaded parts from entering the jig and fixture body.

3: Clearance:

Clearance is provided in the jig or fixture body

(A)   to allow for any variation in component sizes specially casting and forging.

(B)   To allow for hand movements so that the work piece can easily placed in the jig or fixture and removal after machining .

4: Burr Grooves:

A burr raised on the work piece at the start of the cut is termed a minor burr and at the end of a cut is called a major burr. Jigs should be designed so that the removal of the work piece is not obstructed by these burr for this suitable clearance grooves or slots should be provided.

5: Ejectors:

The use of ejection devices to force the work piece out from the jig or fixture is important in two positions.

(A)   the work piece is heavy

(B)   machining pressure forces the work piece to the slides or based on the jig or fixture and the pressure and oil or coolant fill will cause the work to strick and difficult to remove on small jigs and fixtures , a pin located under the work will remove the part radially.

6: Inserts:

To avoid any damage to fragile and soft work piece and also to the finished surfaces of the work piece while clamping. Inserts of some soft material such as copper, lead , fiber , leather , hard rubber and  plastic should be fitted to the faces of the clamps.

7: Design for Safety:

Jigs and fixtures must be safe and convenient in use, following are the some

Factors for the safety of worker working on jigs and fixtures.

(A): Sharp corner on the body of jig and fixture should be avoided.

(B): Sighting surfaces should be cleared.

(C): Bolt and nut should be inside the body of jig or fixture and not protrude on the surface.

8: Sighting Surface:

Machining on the work piece must be clearly visible to the worker. He should not be required to bend is neck for seeing the work piece or work surfaces.

9: Simplicity in design:

Design of the jig and fixture should be a simple one. A completed design require a large maintenance. They should be easily to set , cheap in manufacture.

10: Economical:

Jig and fixtures should be simple in construction, give high accuracy , be sufficiently rigid and lightly weight. To satisfy these conditions an economical balance has to be made.

Cold working processes

Cold working processes:

Below the recrystallization temperature if the mechanical work is done on the metals , there will no grain growth but it must be grain this integration elongation , the process is known is cold working processes. In cold working process greator pressure is required than that required in hot working. As the metal is in a more rigid state. It is not permanently deform until stress exceeds the elastic limit. Most of the cold processes are performed at room temperature , the different cold working processes are

1: Drawing

·        Wire drawing

·        Tube drawing

·        Blanking

·        Spinning

2:  Sequeezing

·        Coining

·        Sizing

·        Riveting

 3:   Bending

·        Angle bending

·        Plate bending

·        Roll forming

 4:  Shearing

      >Punching                >Blanking

           > Trimming               > Perforating

             >Notching                     >Launcing

                >Slittig

5:Extruding

Casting defects

Casting Defects:

The defects in a casting may be due to pattern and moulding box equipment, moulding sand, cores,gating system or molten metal. Some of the defects are:

1: Mould shift

It results in a mismatching of the top and the bottom parts of the casting , usually at the parting line.

2: Swell

It is an enlargement of the mould cavity by molten metal pressure resulting in localized or general enlargement of the casting.

3: Fins and Flash

These are thin projections of the metal not intended as a part of casting. These usually occurs at the parting line of the mould.

4: Sand Wash

It usually occurs near the in the gates as rough lumps on the surface of a casting.

5: Shrinkage

It is a crack or breakage in the casting on the surface of the work piece, which results from un equal contraction of the metal during solidification.

6: Hot Tear

It is an internal or external ragged discontinuously in the metal casting resulting just after the metal has solidified.

7: Sand Blow or Blow Hole

It is smooth depression on the outer surface of the casting work piece.

8: Honeycombing or Slag holes

These are smooth depression on the upper surface of the casting. They usually occur near the ingates.

9: Scabs

These are patches of sand on the upper surface of the casting component.

10: Cold Shut and Misruns

These happens when the mould cavity is not completely filled by the molten and insufficient material or metal.

11: Run-outs and Bust-outs

These permit drainage of the metal from the cavity and result in incomplete casting.

Broach

Broach:

A broach is a multi point cutting tool having a series of cutting teeth or edges which gradually increase in size from the starting or entering end to the rear end. Broaches are used for machining either external or internal surfaces. These surfaces may be produced flat or circular. In broaching, the broach is pushed or pulled over or through a surface of work piece, Each tooth of the tool. A thin slice from surface broaching of inside surface is called internal or hole broaching and outside surfaces is called surface broaching.

Detail of an internal or hole broach:

A typical broach is shown in figure.

It is used to machine an internal hole. The broach is gripped by puller at the shank end. The front rake angle refers a rake angle of a single point cutting tool and back of the angle (relief angle) is provided to prevent rubbing of the tool with the work piece.

High speed steel (Hss) material is widely used to make the broach. It is also raised carbide of disposable inserts or sometime used for cutting edges then machining cost iron parts, which requires close tolerance. Carbide tools are also used to an advantage  on steel cutting. A broach may be either assembled or built up form shells.

Applications for jigs and fixtures

APPLICATIONS FOR JIGS AND FIXTURES

Typically, the jigs and fixtures found in a machine shop are for machining operations. Other operations, however, such as assembly, inspection, testing, and layout, are also areas where work holding devices are well suited. Figure 1-7 shows a list of the more-common classifications and applications of jigs and fixtures used for manufacturing. There are many distinct variations within each general classification, and many work holders are actually combinations of two or more of the classifications shown. EXTERNAL-MACHINING APPLICATIONS:

Flat-Surface Machining

   • Milling fixtures

   • Surface-grinding fixtures

   • Planing fixtures

   • Shaping fixtures

Cylindrical-Surface Machining

   • Lathe fixtures

   • Cylindrical-grinding fixtures

Irregular-Surface Machining

   • Band-sawing fixtures

   • External-broaching fixtures

INTERNAL-MACHINING APPLICATIONS:

Cylindrical- and Irregular-Hole Machining

   • Drill jigs

   • Boring jigs

   • Electrical-discharge-machining fixtures

   • Punching fixtures

   • Internal-broaching fixtures

NON-MACHINING APPLICATIONS:

Assembly

   • Welding fixtures

   • Mechanical-assembly fixtures

     (Riveting, stapling, stitching, pinning, etc.)

   • Soldering fixtures

Inspection

   • Mechanical-inspection fixtures

   • Optical-inspection fixtures

   • Electronic-inspection fixtures

Finishing

   • Painting fixtures

   • Plating fixtures

   • Polishing fixtures

   • Lapping fixtures

   • Honing fixtures

Miscellaneous

   • Layout templates

   • Testing fixtures

   • Heat-treating fixtures

Modular Fixtures

Modular fixtures achieve many of the advantages of a permanent tool using only a temporary setup. Depicted in Figure 1-4, these workholders combine ideas and elements of permanent and general-purpose workholding.

Figure 1-4. Modular workholders combine ideas and elements of both permanent and temporary workholding to make inexpensive-yet-durable workholders.

The primary advantage of modular fixtures is that a tool with the benefits of permanent tooling (setup reduction, durability, productivity improvements, and reduced operator decision-making) can be built from a set of standard components. The fixture can be disassembled when the run is complete, to allow the reuse of the components in a different fixture. At a later time the original can be readily reconstructed from drawings, instructions, and photographic records. This reuse enables the construction of a complex, high-precision tool without requiring the corresponding dedication of the fixture components.

Electric Resistance welding and its types

Electric Resistance Welding

It is a type of pressure welding. It is used for joining pieces of sheet metal or wire. The welding heat is obtained at the location of the desired weld by the electrical resistance through the metal pieces to a relatively short duration, low voltage, high ampere electric current. The amount of current can be regulated by changing the primary turns of the transformer. When the area to be welded is sufficiently heated, the pressure varying from 25MPa to 55MPa is applied to the joining area by suitable electrodes until the weld is solid. The various types of electric resistance welding are as follows:

(1) Spot welding

It is used for welding lap joints, joining components made from plate material having 0.025 to 1.25 mm in thickness. The plate to be joined together are places between the two electrode tips of copper or copper alloy.

(2) Roll spot and seam welding

When the spot welds on two over lapping pieces of metal are spaced, the process of welding is known as roll spot welding. If the spot welds are sufficiently made close, then the process is called seam welding. This process is best for metal thickness ranging from 0.0.25 to 3 mm.

(3) Projection welding

It is similar to spot welding except that one of the metal pieces to be welded has projections on its surface at the points, Where the welds are to be made. In other words it is a multi spot welding process.

(4) Butt welding

The butt welding is of two type :

·        Upset butt welding

·        Flash butt welding

The upset butt welding is especially adopted to rods, pipes and many other components of uniform sections. The flash butt welding is extensively used in the manufacture of steel containers and in the welding of mild steel shanks to high speed drills and reamers.

Rolling mills types

Types of Rolling mills

Rolling mills may be classified according to the number and arrangement of the rolls.

(a): Two high rolling mills

(b): Three high rolling mills

(c): Four high rolling mills

(d): Tandem rolling mills

(e): Cluster rolling mills

1: Two high rolling mills

 Two high rolling mills may further classified as

·        Reversing mill

·        Non reversing mill

A two high rolling mill has two rolls only.

Two high reversing mill:

In two high reversing rolling mills the rolls rotate ist in one direction and then in the other, so that rolled metal may pass back and forth through the rolls several times. This type is used in pluming and slabing mills and for roughing work in plate , rail , structural and other mills.

These are more expensive compared to the non reversing rolling mills. Because of the reversible drive needed.

Two high non reversing mill:

In two high non reversing mills as two rolls which revolve continuously in same direction therefore smaller and less costly motive power can be used. However every time material is to be carried back over the top of the mill for again passing in through the rolls. Such an arrangement is used in mills through which the bar passes once and in open train plate mill.

2: Three high rolling mill:

It consists of a roll stand with three parallel rolls one above the other. Adjacent rolls rotates in opposite direction. So that the material may be passed between the top and the middle roll in one direction and the bottom and middle rolls in opposite one.

In three high rolling mills the work piece is rolled on both the forward and return passes. First of all the work piece passes through the bottom and middle rolls and the returning between the middle and the top rolls.

So that thickness is reduced at each pass. Mechanically operated lifted tables are used which move vertically or either side of the stand. So that the work piece fed automatically into the roll gap.

Since the rolls run in one direction only a much less powerful motor and transmission system is required. The rolls of a three high rolling mills may be either plain or grooved to produce plate or sections respectively.

3: Four high rolling mill:

It has a roll stand with four parallel rolls one above the other. The top and the bottom rolls rotate in opposite direction as do the two middle rolls. The two middle are smaller in size than the top and bottom rolls which are called backup  rolls for providing the necessary rigidity to the smaller rolls.

A four high rolling mill is used for the hot rolling of armor and other plates as well as cold rolling of plates, sheets and strips.

4: Tandem rolling mills:

It is a set of two or three stands of roll set in parallel alignment. So that a continuous pass may be made through each one successively with change the direction of material.

5: Cluster rolling mills:

It is a special type of four high rolling mill in which each of the two working rolls is backup by two or more of the larger backup rolls for rolling hard in materials. It may be necessary to employ work rolls of a very small diameter but of considerable length. In such cases adequate of the working rolls can be obtained by using a cluster mill.

Moulding sand properties and its types

Moulding sand properties and its classification:

The moulding is a process of making a cavity or mould out of sand by means of a pattern. The molten metal is poured into the moulds to produce casting.

Properties of moulding sand

1: porosity or permeability

It is the property of sand which permits the steam and other gases to pass through the sand mould. The porosity of sand depends upon its grain size, grain shape, moisture and clay components are the moulding sand. If the sand is too fine, the porosity will be low.

2: Plasticity

It is that property of sand due to which it flows to all portions of the moulding box or flask. The sand must have sufficient plasticity to produce a good mould.

3: Adhesiveness

It is that properties of sand due to it adheres or cling to the sides of the moulding box.

4: Cohesiveness

It is the property of sand due to which the sand grains stick together during ramming. It is defined as the strength of the moulding sand.

5: Refractoriness

The property which enables it to resist high temperature of the molten metal without breaking down o r fusing.

Classification of Moulding sand according to their use:

1: Green sand

 The sand in its natural or moist state is called green sand. It is also called tempered sand. It is a mixture of sand with 20 to 30 percent clay, having total amount of water from 6 to 10 percent. The mould prepared with this sand is called green sand mould, which is used for small size casting of ferrous and non-ferrous metals.

2: Dry Sand

The green sand moulds when baked or dried before pouring the molten metal are called dry sand moulds. The sand of this condition is called dry sand. The dry sand moulds have greater strength, rigidity and thermal stability. These moulds used for large and heavy casting.

3: Loam Sand

A mixture of 50 percent sand grains and 50 percent clay is called loam sand. It is used for loam moulds of large grey iron casting.

4: Facing Sand

A sand which is used before pouring the molten metal, on the surface is called facing sand. It is specially prepared sand from silica sand and clay.

5: Backing or Floor Sand

A sand used to back up the facing sand and not used next to the pattern is called backing sand. The sand which have been repeatedly used may be employed for this purpose. It is also known as black sand due to its colour.

6: System Sand

A sand employed in mechanical sand preparation and handling system is called system sand. This sand has high strength, permeability and refractoriness.

7: Parting Sand

A sand employed on the faces of the pattern before the moulding is called parting sand. The parting sand consists of dried silica sand, sea sand or burnt sand.

8: Core Sand

The cores are defined as sand bodies used to form the hollow portions or cavities of desired shape and size in the casting. Thus the sand used for making these cores is called core sand. It is sometimes called oil sand. It is the silica sand mixed with linseed oil or any other oil as binder.

Forging defects

Forging defects:

Though forging process give generally prior quality product compared other manufacturing processes. There are some defects that are lightly to come a proper care is not taken in forging process design.

A brief description of such defects and their remedial method is given below.

(A): Unfilled Section:

In this some section of the die cavity are not completely filled by the flowing metal. The causes of this defects are improper design of the forging die or using forging techniques.

(B): Cold Shut:

This appears as a small cracks at the corners of the forging. This is caused manely by the improper design of die. Where in the corner and the fillet radie are small as a result of which metal does not flow properly into the corner and the ends up as a cold shut.

(C): Scale Pits:

This is seen as irregular depurations on the surface of the forging. This is primarily caused because of improper cleaning of the stock used for forging. The oxide and scale gets embedded into the finish forging surface. When the forging is cleaned by pickling, these are seen as depurations on the forging surface.

(D): Die Shift:

This is caused by the miss alignment of the die halve, making the two halve of the forging to be improper shape.

(E): Flakes:

These are basically internal ruptures caused by the improper cooling of the large forging. Rapid cooling causes the exterior to cool quickly causing internal fractures. This can be remedied by following proper cooling practices.

(F): Improper Grain Flow:

This is caused by the improper design of the die, which makes the flow of the metal not flowing the final interred direction.