What is Quality?

           Everybody now- a- days takes of Quality, thinks about it and insists for it while purchasing any article. To buy anything we all look for good quality at a reasonable price. Each of us may have a different notion about the quality product. We want as many of the qualities in a product as possible. Quality product or quality service should be provide at an affordable price.

         Question is how we can define quality? In very simple words we may say that quality means " Fitness of use ". So when we talk of quality we mean that the product should be fit for use and it is the user who judges and decides wants in the product. Thus quality is customer's determination and the quality products are those which totally satisfy the needs and expectations of customer in every respect on continuous basis.

         All human institutions, such as factories, schools, hospitals, temples, governments, etc. Exist to products or services to human beings. What is essential in these products or services is that they should be fit for use and provide excellence in service. Such products should be well designed with functional perfection and be produced right in the first instance. If a hospital is well equipped but not serving up to your expectations then the service is not good or the quality of service is poor. If  a factory produces the cars, which give lot of trouble and do not run properly then the car is not fit for use in the real sense or you say the quality of the car is poor. So, whether it is a product or a service it should be fit for use or should be of good quality.

According to ISO: 8402, quality is defined as the totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs. There has been a wrong notion in minds of a few that quality can be achieved at higher cost. on the other hand experience has shown that it is poor quality that implies waste of material, effort of labor, equipment utilization and thus results in higher cost. One must remember that quality has to be created.

Quality Characteristics:

           Now, let us examine a little more in detail as to what quality. The quality of a product comprises several engineering and manufacturing characteristics which go to make the product meet the ultimate performance expectations of the designer / customer.

What is characteristic?

o   A dimension is a characteristic.

o   A chemical property is a characteristic.

o   A sensory property is a characteristic.

All these characteristics contribute towards the quality of the product. So we can say that appearance of a product is a quality characteristic of the product. Similarly performance, length of life, dependability, reliability, maintainability, the smell, taste, feel, sound, etc. are all characteristic which go to build the quality of the product. Each of these characteristics is like a building block that goes into the construction of, say an arch which may be considered to be quality.

now, for any product to be successful, apart from quality the price also should be reasonable from the buyer's point of view. Today, quality is becoming significant factor in the business strategy planning process.   

Non-ferrous material

Introduction:

Unlike mild steel, non-ferrous Mattel do not in general display the discontinuity of yield point in the stress-strain curve. Appealed alloys may pass through a period of more rapid extension but cold worked metals pass imperceptibly from the proportional relationship to the condition where plastic flow has occurred, and the whole curves is smooth. For such material the yield strength is usually found by determining the load necessary to produce a specified total elongation.

An important method of increasing the strength and hardness of non-ferrous metals is by cold working in which the grains flow by a process involving the slip of blocks of blocks of atoms over each other, along definite crystallographic planes.  Many alloys can be hardened and strengthened by heat - treatment consisting of two-step process. First the alloy is given a solution heat-treatment followed by rapid quenching, and then a precipitation or ageing treatment is given to cause separation of second phase from solid solution and hardening. These alloys after a solution treatment are comparatively soft and consist of homogeneous grains of solid solution generally indistinguishable microscopically from a pure metal. Rapid cooling after solution treatment retains the supersaturated solution at room temperature, and if the alloy be subsequently reheated to a suitable temperature, fine particle of a new phase are formed and in time will grow to a microscopically resolvable size. At some stage in this precipitation process, the hardness, the tensile strength, and particularly the yield strength will be considerably increased.

Copper:

Copper is a very important metal in industry as has great corrosion resistance property. It has got good strength which is maintain at moderate temperature. It is very ductile and can be worked in to complex shapes. It can be very easily welded, soldered and riveted. It has got very high heat conductivity and electrical conductivity.

Material Properties:

	Annealed	Cold worked
Tensile strength kg/cm2	2000 - 2250	3000 - 4500
Hardness brinell	45 - 55	80-100
Elongation percent on 50mm	50-60	5-20
Modulus of Elasticity	0.95 to 1.2 x 106 kg/cm2	0.95 to 1.2 x 106kg/cm2

Copper and its alloys can be easily joined by soldering, brazing and welding.

Refining of copper:

           Blister copper, as obtained after roasting and converting the copper ore, contains about 98.5% copper and the rest 1.5% is made up of nickel, iron, selenium, lead, arsenic, antimony, bismuth, sulphur, precious metals, etc. Such a copper cannot be used in industry. So it is further refined by the processes in the sequence given below:

(1) Fire Refining: in order to produce purer and homogeneous anodes.

(2) Electrolytic Refining: For refining precious metals and removing the impurities.

(3) Second Firing: For adjusting the physical properties of electrolytic copper for use in industry.

After electrolytic refining operation, cathodes may be used directly for making alloys, but if copper is to be rolled to fabricated forms, it is melted and cast into wires, bars, billets. After the second firing operation, the correctly refined castings solidify with an approximately - level surface, the gas evolved during solidification balancing the shrinkage that would otherwise occur. This is known as though-pitch copper and has a density of  8.4 to 8.7 g/cc when cast, 8.89 to 8.92 when worked and annealed.

Types of Copper:

(1) High conductivity copper.

(2) Best select copper.

(3) Arsenical copper.

(4) Deoxidised copper.

Uses of copper:

Copper is used in huge quantity for making copper wire. It is used for making alloys such as brass. On account of its high resistance to corrosion, it is used in the form of copper sheets in chemical work, and food and brewing plants.

Copper can be cold rolled extensively up to 870ºC and beyond it hot-worked. Cold rolling increases the hardness and strength. Copper wire above 0.10mm diameter is commonly made by drawing from a hot-rolled rod without annealing but smaller size involve intermediate anneals. Copper shapes for electrical switch parts are made by extrusion, brushes and commutator sections by rolling and drawing.

Copper containing small amounts of silver or antimony retains the properties attained by cold working to a higher temperature than pure copper. This is useful where comparatively high temperature are to be withstood, as in soldering or enamelling operations.

Lead:

Lead is obtained from its ores, by concentration, floatation, and reduction in blast furnaces. The crude lead is purified by washing with molten zinc, and the resulting lead is cast into pigs.

Properties of lead:

Lead is a soft and weak metal. its tensile strength is about 150 kg/cm². It is very malleable and ductile. It is very heavy and resists corrosion. It has high density, low melting point and high boiling point. It can be easily melted(melting point 327ºC), cast, rolled and extruded. It is highly malleable and pliable. So it is easily melted during fabrication and installation. It has low strength and due to that its ductility is also low. It has got low elastic limit, high coefficient of thermal expansion and got very high anti-frictional properties. It is a good insulator against nuclear radiation. Impurities present in lead are very small but have profound effect chemically. Based on the content of impurities lead can be classified in to the following groups:

(1) Corroding lead.

(2) Chemical lead.

(3) Tellurium lead.

(4) Antimonial lead.

Uses of lead :

(1) Lead is used in the manufacture of a number of chemicals. (ex) it is used for lining in the tank, when ground bauxite is treated with sulphuric acid for manufacturing alum, etc. The heating Coil is also made of lead.

(2) It is used Battery plates.

(3) Lead can be safely used in various processes where it comes in contact with the following  chemical:

    (a) Solvents such as alcohols, acetone, trichloroethylene, etc.

    (b) Acids such as sulphuric acid, chromic acid, hydrofluoric acid, etc.

    (c) Alkalise such as ammonium hydroxide, sodium hydroxide, etc.

(4) It is introduced into alloys to produced free-cutting characteristics.

(5) In paint industry lead is used as oxide of basic carbonate as pigment. 

Aluminium:

 

   

 First stage in the production of aluminium is the production of alumina by chemical refinement of bauxite. Aluminium is then produced by the electrolysis of alumina dissolved in a bath of molten cryolite. It is available in the market as wrought and cast products in the form of ingots or notched bars for remelting. It is possible to obtain over 99.97% pure aluminium commercially.

Properties of Aluminium:

Physical properties: Aluminium is a silver white metal. Its outstanding properties are lightness good electrical and thermal conductivity. It is a good reflector of light and a good radiator of energy. It is non-magnetic. It is resistant to atmospheric attack. Oxide film that is set up upon exposure to air insulates it against continued attack. It has good tensile strength in the form of alloys. Due to its ductility it can be easily worked. By itself it is very weak and ductile and metals at 660ºC. It's tensile strength is 600kg/cm² but it can be increased by cold working.

Aluminium is generally 99.9% pure as obtain by hall-heroult process and impurities of iron and silicon present from alloy with aluminium. Pure aluminium is silvery white in colour but commercial aluminium due to impurities has got a bluish tinge.  

Chemical Properties:

It is resistant to atmosphere due to the formation of a protective oxide film. This oxide film is very thin, less than 0.02micron (µm) in thickness but is impervious and highly protective. On heating, this film increase in thickness. Heat of combination of aluminium with oxygen is very high. Finely divided powered aluminium burn in air.

 Uses and Engineering Application:

(1) Chemical and Food Industry:

           Aluminium is resistant to many mineral and organic acids, salt solutions, organic compounds, sulphur and many other substances. Aluminium is available in different fabricated forms and it can be assembled and finished by different processes. Due to all these reasons it is used for fabricating equipment for chemical and food processing industries.

(2) Metallurgical Industries:

           Aluminium is used in the metallurgy of iron and steel as it is a powerful deoxidizer and reduces the dissolved and combined oxygen content of molten steel.

(3) Structural Application:

          Due to its light weight and high tensile strength it is used for the construction of aeroplanes, Buses, Tracks, Trains and ships.  

(4) Aluminium also used in Electrical industry, Brewery industry.

Nickel:

Properties of Nickel:

Nickel is a hard, lustrous, white metal. It fuses at 1484ºC. It can take up high polish and is stable in dry air. However, when exposed to dampness, it tarnishes. It is not attacked by alkalis. Cast nickel contains carbon which makes it non-malleable. Its electrical conductivity is less than iron. It is magnetic and is more resistant to corrosion and to loss of strength due to heating in comparison to iron.

The ease with nickel can be cast, machined, spun, drawn into wire, forged, welded, brazed soft and silver-soldered, makes it as good as mild steel. Nickel is used in large quantities due to its higher resistance to even highly corrosive solutions.

Physical properties:

Specific gravity	8.9
Melting point	1458ºC
Tensile strength	3700 kg/cm2
Thermal conductivity at 100ºC	0.145
Thermal conductivity at 290ºC	0.128
Specific heat mean 0 to 100ºC	0.1147
Coefficient of linear expansion between 25 to 100ºC	1.33x10-6

Zinc:

Zinc is a weak metal . Zinc tensile strength is 1550kg/cm². It resists corrosion due to formation of a dense layer of corrosion product which insulates it against continued corrosion.

Uses of Zinc:

Zinc is used as a protective coating for steel. Zinc is applied on steel by hot dipping or by electroplating . It is used in the form of rolled sheets for rooting and battery containers, and as a lining for transportation cases, because it can be made water and air-tight and is proof against insects, etc.

Tin:

Properties of tin:

Specific gravity	7.285
Melting point	232ºC
Tensile strength	130kg/cm2

   It is soft metal having very low tensile strength. When cold it is quite brittle and it cracks when it is bent. It is malleable at about 100ºC.At this temperature it can be rolled into sheets or drawn into pipes.

Uses of Tin:

(1) As it is not corroded by water and organic acid, it is used for lining  copper and iron tanks and also cooking vessels. it is plated on iron sheets.

(2) it is used to form very useful alloys such as solder, bell metal, bearing alloys etc.

 

Thermo dynamic property

Property:

The quantities which characteristic the given state of the system are called properties or parameters. A property can be measured directly or in directly while the system is in equilibrium. The valve of the property depends only on the state and not on the process or path by which the state is achieved. Temperature, pressure, viscosity, velocity, thermal connectivity, volume, mass, enthalpy and entropy are some of the properties. Heat and work are not properties as they are functions of path.

Thermodynamic property are classified into two groups intensive and extensive properties. An intensive property is independent of the mass and an extensive property varies directly with the mass. (E.X) If a matter in a particular state is divided into two equal parts will have the same properties. Temperature, pressure and density are example of intensive properties and mass and volume are examples of extensive properties.

Force:

Thermodynamic property can be measured and counted either directly or indirectly. Properties such as force, mass, length time have the basic units and are related. NEWTON'S SECOND LAW OF MOTION states that the force acting on a body is the product of the mass and the acceleration of the body in the direction of the force.

F = ma

The popular system of units in use presently throughout the world is the international system and referred ad SI units. Matter, second and kilogram are the basic units for length, time and mass respectively.

    The unit of force is Newton (N) and

                                    1 N = 1kg m/s²

Density:

Density is defined as the ratio of mass per unit volume. The density varies significantly for a gas with pressure and temperature but the variation is negligible for liquids.

Specific Weight:

Specific weight (w) is defined as the ratio of weight per unit volume.

      Specific weight, w = weight/ volume ( N/m³)

Specific Gravity:

    Specific gravity of a liquid is defined as the ratio of specific weight of that liquid to the specific weight of water.

Specific Volume:

Specific volume of a substance is defined as the volume per unit mads. The density of a substance, defined as the mass per unit volume, is the reciprocal of the specific volume. Specific volume and density are intensive properties.

The SI unit for volume is cubic metre. The other volume unit is the litre and is equal to 0.001cubic metres.

Specific Heat:

Heat required to raise the temperature of 1kg of a gas by 1ºC while the volume of the gas remains constant is known as the specific heat at a constant volume

 ( cᵥ' ) and if the gas expands at a constant pressure then it is called the specific heat at a constant pressure ( Cp' ). The specific heat of a gas at a constant pressure is always greater than the specific heat at a constant volume.

Viscosity:

The property which controls the rate of a liquid is known as viscosity. Viscosity is due to the cohesive force between the liquid particles and it is exhibited when the liquid is in motion. Newton's law of viscosity states that the shear stress on a layer of a fluid is directly proportional to the rate of shear strain.

            shear stress, τ α dv/dy   →   τ = µ dv/dy

Where dv/du is the rate of shear strain or velocity gradient and µ is the proportionality constant known as coefficient of viscosity. µ is also known as coefficient of absolute viscosity or dynamic viscosity. The unit of µ is Ns/m² also

             1 poise = 0.1 Ns/m² and

             1 centipoise = (1/100)poise

             τ = µ dv/dy = (Ns/m²) (m/s/m) = N/m²

Kinematic viscosity of a liquid is the ratio of its absolute viscosity to its density.

             Kinematic viscosity  γ = µ/ρ,  m²/s

                     1 Stroke = 1/10000 m²/s = 10^-4 m²/s

                     1 Centistoke = 1/100 stoke

Pressure:

Pressure is defined as the normal component of force per unit area. Pressure at a point in a fluid in a equilibrium is the same in all directions.

A fluid filled in a container exerts a force at all points on the sides and bottom of the container. This force per unit area is called pressure. The direction of this pressure is always normal to the surface with which the fluid comes in contact.

Autospheric pressure:

The pressure exerted by the weight of air column on the surface of the earth is called as atmospheric pressure.

Atmospheric pressure = weight of air column / area

=mass of air column X acceleration due to gravity/area

= (Volume of air column X Density of air column X Acceleration due to gravity) / Area

= Height of air column X Density of air column X Acceleration due to gravity

= hρg {m(kg/m³)(m/s²)  = (N/m²)}

Since the acceleration due to gravity g is constant (g = 9.81 m/s² ), the atmospheric pressure at any location depends on the height of air column and density of air at that place. The value of atmospheric pressure is considered as standard at the surface of the sea as it is horizontal everywhere. The maximum air column height exists at the sea level and value of standard atmospheric pressure is 1.03*10⁵ N/m² or 1.03 kg/cm² . The value of atmospheric pressure will be less than this at any other places on earth due to temperature zones due to pressure difference. This is how wind is formed.

Gauge pressure:

Pressure measuring instruments are usually calibrated with respect to atmospheric pressure. They Will read zero at atmospheric pressure. Pressure measured with these gauge is known as gauge pressure. Pressure gauge are used to measure pressure above atmospheric level and vacuum gauges are used to measure pressure below atmospheric level.

Absolute pressure:

Absolute pressure is the sum of gauge pressure and atmospheric pressure. Absolute pressure is zero at absolute vacuum.

Absolute pressure = gauge pressure+ absolute pressure

   The unit for pressure in the international system is ( force in newton acting on a square meter area) called the pascal (Pa).

                          1 Pa = 1N/m2

The other units are:

                          1bar = 10⁵ Pa = 0.1 MPa and

       1atm = 101325 Pa = 14.696 lbf/in2 (or) Psi.

Measurement of Exhaust Emission

        Exhaust gas emissions are monitored satisfy the legislation on pollution and also because of the insights the measurement provide into engine performance. The emissions governed by legislation on pollution are carbon monoxide, nitrogen oxides, unburnt hydrocarbons and particulates. Carbon dioxide and oxygen level in exhaust will help to calculate the air/fuel ratio.

CO Measurement:

Infrared radiation is absorbed by a wide range of gas molecules including CO and each of which has a characteristic absorption spectrum. Fig it shows the component in a non-dispersive infrared gas analyser. The detector cells are fitted with the gas that is to be measured such as carbon monoxide. They absorb the radiation in the wavelength band associated with that gas. The energy absorbed in the detector cells causes the cell pressure to rise. The reference cell is filled with air and the gas to be analysed flows through the sample cell. If carbon monoxide is preset in the sample, than infrared will be absorbed in the sample cell and less infrared will be absorbed in the detector cell. This leads to the carbon monoxide concentration. The calibration is determined by passing gases of known composition through the sample cell.

NO measurement:

Nitric oxide and nitrogen dioxide exist in the exhaust of an engine and NO is used to refer to the sum of the nitrogen oxides. Nitrogen dioxide can be measured by passing the sample through a catalyst that converts the nitrogen dioxide to nitric oxide.

It shows the arrangement of the NO analyser. The vacuum pump controls the pressure in the reaction chamber by drawing in the ozone and exhaust sample. Ozone is generated by electrical discharge in oxygen at low pressure. Flow of ozone is controlled by the oxygen pressure and the orifice. The sample can either bypass or flow through the nitrogen dioxide converter. The sample flow rate is regulated by two orifices. The bypass flow is drawn through by a sample pump. This arrangement ensures a high flow rate of sample gas, so as to minimize the instrument response to to a change in NO concentration in the sample. The flow of sample into the reactor is controlled by the pressure differential across the orifice upstream of the NO converter and controlled by the regulator.

Oxygen and air/fuel ratio analysers:

Oxygen measurement in exhaust emission is useful in evaluating the air/fuel ratio and the oxygen analysers are usually based around a galvanic cell. A galvanic cell comprises a PTFE memberane with a gold coating that acts as the cathodeas shown (fig 4.15). A silver or lead anode is immersed in the electrolyte. A potential is applied across the electrodes and the oxygen diffuses through the memberane. Oxygen is reduced electrochemically and a current flows proportional to the partial pressure of the oxygen in the sample.

Particulates and smoke emission:

The most widely used system is the Bosch Smokemeter. A controlled volume of exhaust is drawn through a filter paper and the change in the reflectance of the paper corresponds to the smoke level. A value of zero is assigned to a clean filter paper and a value of 10 is assigned to a piece of paper that reflects no light. The calibration of intermediate values can be checked by placing a perforated piece of non-reflecting paper over a filter paper.

Exhaust particulates are defined as material that can be collected on a filter paper maintained at 325K. It is impractical to pass the whole of the exhaust stream through the filter. A sample of the exhaust is drawn off and cooled by dilution with air. The filter is weighed before and after use and the mass of the particulates is evaluated. The particulates consist of particles and high molecular mass hydrocarbons.

It is not the mass of particulate matter that is significant, but it's size or number of particles is quite significant. The smallest particles have the ability to travel furthest into human lungs. Particulate matter above 10µm  is mostly filtered by the nasal passages but some of the particles below this size will penetrat into the pulmonary and bronchial systems and be deposited there. It is generally accepted that particles below 2.5µm are capable of penetration deep into the lungs and can thus pose a health hazard. Particles of this size are invisible and are in fact emitted by both spark ignition and diesel engines.

Drilling Machine

Drilling Machine:

Introduction

Drilling machine is one of the simplest, moderate and accurate machine tool used in production shop and tool room. It consists of a spindle which imparts rotary motion to the drilling tool, a mechanism for feeding the tool into the work, a table on which the work rests and a frame. It is considered as a single purpose machine tool since it's chief function is to make holes.

Drilling is a process of making hole or enlarging a hole in an object by forcing a rotating tool called drill

Specification of drilling machine

o   Portable drilling machine is specified by the maximum diameter of drill which can be held.

o   Sensitive and upright drilling machine are specified by the diameter of the largest work piece that can be drilled.

o   The radial drilling machine is specified by the length of the arm and column diameter.

o   Multiple spindle drilling machine is specified by the drilling area, the size and the number of holes a machine can drill.

Operations Performed

     o    Reaming

     o   Boring

     o   Counter Boring

     o   Counter sinking

     o   Spot Facing

     o   Tapping

  o      Trepanning

     o   Rivet spinning

     o   Polishing

Classification of Drilling Machines

This machines are classified in based on construction and the work performed.

Portable Drilling Machine:

It is small compact drilling machine used principally for drilling operations which can be performed on a regular drill press. The most renewed example of this class is the hand drill. It is equipped with a small electric motor which gives power while working and is specified by the maximum drilling capacity.

Sensitive Drilling machine:

It is a light, simple, bench type machine for light duty working. It is usually supplied with a friction drive to give an infinite speed ratio. The horse power is small. 800 to 9000rpm is a typical range of this machine, with the maximum drilling capacity of 12.5mm. The major components of this machine are Spindle, Column, table and the base. Machine of this type are usually hand fed and operate on the principle of rack and pinion drive. The drill head is counterbalanced and fed through a hand lever system. This arrangement allows the operator to feel the force acting on the drill and hence the term 'sensitive'. 

Upright or column Drilling Machine

these are similar to sensitive drilling machines, except that they have power feeding mechanism for rotating the drill and are designed for heavier work. Generally these machines have box type column which is more rigid and consequently adapted for heavier work. The table can be given precise movement by a lead screw and graduated sleeve system.

It has several spindle speeds offered in several speed ranges from 75 to 3500rpm. The feed clutch is automatically controlled so that spindle will be disengaged when it reaches its upper and lower limit of travel. It has also free engagement of taps through clutch and rapid reversing mechanism for withdrawals. Such a machine is ideally suited for small and big shops. The size of the work that can be accommodated is limited by the distance between the spindle and the column.

Radial drilling machine:

It is the largest and most versatile of the drilling machines and is very well suited for drilling large number of holes. It is a single spindle machine intended for handling large and heavy work or work which is beyond the capacity of the small drilling machine. It consists of vertical column with a radial arm that can be swung through an arc of 180⁰ or more. On the radial arm, which is power driven for vertical movement, is an independently driven drilling head equipped with a power feed. The drilling head may be moved along the arm hand or power gear and rack arrangement. To drill a hole the following procedure is followed. The arm is raised or lowered as needed, the drill head is positioned and locked on the arm, the arm is locked in that position, the spindle speed and feed are adjusted, and the depth is set. The drill will then feed down and return when the proper depth has been reached. The arm and column may then be unlocked and the drilling head moved to a new position without disturbing the work. Universal radial drills allow the radial arm to be rotated on a horizontal axis, providing the angular hole drilling. Spindle speeds ranging from 20 to 1600rpm and feed from 0.05 to 3mm per revolution are available. Sometimes the drilling head is provided with a swivelling arrangement to facilitate angular cutting.  

Gang Drilling Machine:

Gang drilling machines have two or more drill heads mounted on the same table. These can be run either simultaneously or in sequence. Spindles are lined in a row, driven either manually or by power. Each spindle can be independently set for speed and depth. Such a machine is useful when a work-piece is to have several operations performed, such as drilling, counter boring, reaming etc,. or for drilling holes of several different sizes. It is adopted for short runs, where tooling cost of a multi-spindle machine is too great. Fast movement of the work from one spindle to another is an important feature of this machine. The number of spindle is practically unlimited, but the four spindles are the most common. Machines of this type are used for any straight line, multiple hole drilling applications, as in pipes, channels, casting, angles and plates.

Multi-spindle Drilling machine:

These have been developed for the purpose of drilling several holes simultaneously. These machine are essentially production machines, and once set-up, will drill many parts, with such accuracy that all the parts are inter changeable. Multi-spindle machines differ in the drills are held and the way in which feed is accomplished.

Generally multi-spindle machines are of vertical type. The head assembly has number of fixed upper spindle driven by pinions surrounding a central gear. A corresponding number of spindle are located below this gear and are connected to the upper ones by a tubular drive-shaft and two universal joints. These, thus can lower the spindles. The drills may be adjusted over a wide area. the entire head assembly carrying all the spindles travels on vertical double-V ways. In some machines, table moves upwards and drilling heads are fixed. The drilling cycle consists of the rapid advance of drills to the work, proper feed, and rapid return of drills to the starting position. For drilling closely spaced holes, some of the holes are drilled first by a set of spindles, the job is then repositioned and other set of closely spaced holes are then drilled by the another set of spindles. A special type of multi-spindle machine is way-type. It has usually two, three or four ways, each of them is inclined at same angle. When several holes in different planes are to be drilled, this type of machine is needed.

Vertical turret type Drilling machine:

This machine has a turret which houses various tools such as drill, ream, spot-face, counter bore, tap in any desired sequence. The various spindle on this indexing turret can be indexed manually or automatically. These spindles cannot be driven until they come to the drilling position.

Automatic Drilling machine:

These are used for high production work. These are built of a number of unit heads with single or multiple spindles in angular, horizontal or vertical positions in various combination on a special base. Indexing table and work holding fixture at each station are also provided.

Deep Hole drilling machine:

These machines are used for drilling such holes whose length exceeds three times the drill size. The example of this class are rifle barrels, long spindles, connecting rods and certain oil-well drilling equipment. They are of horizontal type, single spindle or multi-spindle and may vary as to whether the work or the drill is made to revolve.