UNIT III RECIPROCATING AND MILLING MACHINES

SYLLABUS Reciprocating machine tools: shaper, planer, slotter; milling: types, milling cutters, operations; hole making: drilling, reaming, boring, tapping SHAPER: INTRODUCTION The shaper is a reciprocating type of machine tool intended primarily to produce flat surfaces. These surfaces may be horizontal, vertical, or inclined. In general, the shaper can produce any surface composed of straight line elements. Modem shapers can generate contoured surface. TYPES OF SHAPERS Shapers are classified in a number of ways depending upon the general features of design or the purpose for which they are intended. Shapers are classified under the following headings. 1 .   According TO THE TYPEOF MECHANISM used for giving reciprocating motion to the ram: 

Crank type Geared type Hydraulic type 2. According to the position and travel of ram: Horizontal type Vertical type Traveling head type. 3. According to the type of design of the table: Standard shaper Universal shaper 4. According to the type of cutting stroke: Push type D r a w t y p e CRANK SHAPER This is the most common type of shaper in which a single point cutting tool is given a reciprocating motion equal to the length of the stroke desired while the work is clamped in position on an adjustable table. In construction, the crank shaper employs a crank mechanism to change circular motion of a large gear called “bull gear” incorporated in the machine to reciprocating motion of the ram. The bull gear receives power either from an individual motor or from an overhead line shaft if it is a belt driven shaper. SHAPER SIZE The size of a shaper is determined by the maximum length of stroke or cut it can make.

The usual size ranges from 175 to 900 mm, Length of stroke indicates be adjusted from 0 to 250 mm, The cross feed adjustment of the table will be 250 mm The extreme bottom position of the cross rail will permit the table to accommodate a work piece 250 mm high. S H A P E R M E C H A N I S M In a standard shaper metal is removed in the forward cutting stroke, while the return

stroke goes idle and no metal is removed during this period. To reduce the total machining time it is necessary to reduce the time taken by the return

stroke. During the return stroke it can allow the ram to move at a faster rate to reduce the idle

return time. This mechanism is known as quick return mechanism

The reciprocating movement of the ram and the quick return mechanism of the machine are usually obtained by any off of the following methods: Crank and slotted link mechanism Whitworth quick return mechanism Hydraulic shaper mechanism CRANK AND SLOTTED LINK MECHANISM: The motion or power is transmitted to the bull gear 14 through a pinion. Which receives its motion from an individual motor or overhead line shaft through control speed of the bull gear may be changed by different combination of gearing or by simply shifting the belt on the step cone pulley. WHITWORTH QUICK RETURN MECHANISM The Whitworth quick return mechanism and a simple line diagram of the mechanism. The bull gear is mounted on a large fixed pin A upon which it is free to rotate. The crank plate is pivoted eccentrically upon the fixed pin Fitted on the face of the bull gear is the crankpin on the top of which is mounted the sliding block. Sliding block fits into the slot provided on the crank plate at the other end of the crank plate. Connecting rod connects the crank plate by a pin HYDRAULIC SHAPER MECHANISM: •In a hydraulic shaper the ram is moved forward and backward by a piston moving in a cylinder placed under the ram. •The machine mainly consists of a constant discharge oil pump •A valve chamber, a cylinder, and a piston

•The piston rod is bolted to the ram body. •The oil under high pressure is pumped from the reservoir and is made to pass through the valve chamber to the right side of the oil cylinder S Exerting pressure on the piston. •This causes the ram connected to the piston to perform forward stroke. A hydraulic shaper now widely used for having many advantages. Some of them are listed below.

i. The cutting and return speeds are practically constant throughout the stroke. This permits the cutting tool to work uniformly during cutting stroke.

ii. The reversal of the ram is obtained quickly without any shock as the oil on the other end of

the cylinder provides cushioning effect. iii. Infinite number of cutting speeds may be obtained from zero to the maximum value and

the control is easier. iv. With a high rate of return speed, a greater number of cutting strokes may be available

within the range of cutting speed. v. The relief valve ensures safety to the tool and the machine when the machine is

overloaded. FEED MECHANISM: In a shaper both down feed and cross feed movements may be obtained. Unlike a lathe, these feed movements are provided intermittently and during the end of return stroke only. Vertical or bevel surfaces are produced by rotating the down feed screw of the tool bead by hand .Cross feed movement is used to machine a flat horizontal surface. This is done by rotating the cross feed screw either by hand or power Rotation of the cross feed screw causes the table mounted upon the saddle to move sideways through a predetermined amount at the end of each return stroke so as to bring the uncut surface of the work in the direct path of the reciprocating tool.

PLANER MACHINE

•A planer is very large and massive compared to a shaper and capable of machining heavy work pieces which cannot be accommodated on a shaper table • The fundamental difference between a shaper and a planer is that in a planer the work which is supported on the table reciprocates past the stationary cutting tool and the feed is supplied by the lateral movement of the tool,

•The planning machine was developed by Richard Roberts, an Englishman in the year 1817.The design and working principle of the machine, of course, was almost identical to the present day machine. TYPES OF PLANING MACHINE Different classes of work necessitate designing of different types of planning machine to suit to various requirements of our present day industry. The different types of planer which are most commonly used are:

a) Double housing planer. b) Open side planer. c) Pit planer Edge or plate planer. d) Divided table planer.

STANDARD OR DOUBLE HOUSINGPLANER: •The standard or double housing planer is most widely used in workshops. •A double housing planer has a long heavy base on which a table reciprocates on accurate guide ways. The length of the bed is little over twice the length of the table. •Two massive vertical housings or uprights are mounted near the middle of the base, OPENSIDE PLANER:

An open side planer has a housing only on one side of the base and the cross rail is suspended from the housing as a cantilever.

This feature of the machine allows large and wide jobs to be clamped on the table and reciprocated past the cutting tool.

One side of the planer being opened, large and wide out of the table and reciprocate without being interfered by the housing.

In a double housing planer, the maximum width of the job which can be machined is limited by the distance between the two housings.

PIT PLANER: A pit type planer is massive in construction. It differs from an ordinary planer in that the table is stationary and the column carrying the cross rail reciprocates on massive horizontal rails mounted on both sides of the table. This type of planer is suitable for machining a very large work which cannot be accommodated on a standard planer and the design saves much of floor space. EDGE OR PLATE PLANER: The design of a plate or edge planer is totally unlike that of an ordinary planer. It is specially intended for squaring and beveling the edges of steel plates used for different pressure vessels and ship-building works. One end of a long plate which remains stationary is clamped with the

machine frame by a large number of air operated clamps. The cutting tool is attached to a carriage which is supported on two horizontal ways of the planer on its front end. DIVIDED TABLE PLANER: This type of planer has two tables on the bed which may be reciprocated separately or together. This type of design saves much of idle time while setting the work. The setting up of a large number of identical work pieces on the planning machine table takes quite a long time. It may require as much time for setting up as may be necessary for machining. To have a continuous production one of the tables is used for setting up the work, while the other reciprocates past the cutting tool finishing the work. SIZE OF A PLANER •The size of a standard planer is specified by the size of the largest rectangular solid that can reciprocate under the tool. •The size of the largest solid is known by the distance between the two housings, the height from the top of the table to the cross rail in its uppermost position, and the maximum length of table travel. •The length of the table always almost equal to the table travel. •Double housing planers range from 750mm x 750mm x 2.5m at the smallest up to 3000mm x3000mm x 1825m at the largest size. •Usually the distance between the housings and the height from the table to the cross rail in its highest position are equal. • For this reason a planer may be roughly specified as 750 mm planer or 3000 mm planer. PLANER MECHANISMS The two important mechanisms of a planer are:

a) Table drive mechanism. b) Feeding mechanism.

The different mechanisms used to drive the table are:

i. Open and cross belt drive. ii. Reversible motor drive.

iii. Hydraulic drive. OPEN AND CROSS BELT DRIVE: The open and cross belt drive of the table is used in a planer of smaller size where the table width is less than 900 mm. It illustrates the elevation and sectional plan of the mechanism. The sectional plan shows that the gearing arrangement is contained within the bed.

MILLING MACHINES INTRODUCTION Milling machine is a machine tool that removes metal as the work is fed against a rotating multipoint cutter. The cutter rotates at a high speed and because of the multiple cutting edges it removes metal at a very fast rate. The first milling machine came into existence in about 1770 and was of French origin. The milling cutter was first developed by Jacques de Vaucanson in the year 1782. The first successful plain milling machine was designed by. Eli Whitney in the year 1818 Joseph R Brown a member of Brown and Sharpe Company invented the first universal milling machine in the year 1861. TYPES OF MILLING MACHINE 1 . C o l u m n a n d k n e e t y p e . Hand milling machine. Plain milling machine. Universal milling machine. Universal milling machine. Vertical milling machine. 2. Manufacturing of fixed bed type. Simplex milling machine. Duplex milling machine. Triplex milling machine. 3. Planer type. 4. Special type.  Rotary table milling machine. Drum milling machine Planetary milling machine. Pantograph, profiling & tracer controlled milling machine. Column and knee type For general shop work the most commonly used is the column and knee type where the table is mounted on the knee-casting which is in turn is mounted on the vertical slides of the main column.

The knee is vertically adjustable on the column so that the table can be moved up and down to accommodate work of various heights. The column and knee type milling machines are classified according to the various methods of supplying power to the table different movements of the table and different axis of rotation of the main spindle. HAND MILLING MACHINE: The simplest of all types of milling machine is the hand miller in which the feeding movement of the table is supplied by hand control. The cutter is mounted on a horizontal arbor and is rotated by power, The machine is relatively smaller in size than that of other types and is particularly suitable for light and simple milling operations such as machining slots, grooves and keyways. PLAIN MILLING MACHINE: The plain milling machines are much more rigid and sturdy than hand millers for accommodating heavy work pieces. The milling machine table may be fed by hand or power against a rotating cutter mounted on a horizontal arbor. A plain milling machine, having horizontal spindle, is also called horizontal spindle milling machine. In a plain milling machine, the table may be fed in a longitudinal, cross or vertical directions. OMNIVERSAL MILLING MACHINE: A universal milling machine is so named because it may be adapted to a very wide range of milling operations. A universal milling machine can be distinguished from a plain milling machine in that the table of a universal milling machine is mounted on a circular swiveling base which has degree graduations, and the tale can be swiveled to any angle up to 450 on either side of the normal position. The table can be swiveled about a vertical axis and set an angle other than right angles to the spindle. Thus in a universal milling machine, in addition to three movements as incorporated in a plain milling machine, the table may have a fourth movement when it is fed at an angle to the milling cutter. UNIVERSAL MILLING MACHINE: In this machine, the table besides having all the movements of a universal milling machine can be tilted in a vertical plane by providing a swivel arrangement at the knee.

The entire knee assembly is mounted in such a way that it-may be fed in a longitudinal direction horizontally. The additional swivelling arrangement of the table enables it to machine taper spiral grooves in reamers, bevel gears, etc. It is essentially a tool room and experimental shop machine. VERTICAL MILLING MACHINE: •A vertical milling machine can be distinguished from a horizontal milling machine by the position of its spindle which is vertical or perpendicular to the work table. •The machine may be of plain or universal type and has all the movements of the table for proper setting and feeding the work. •The spindle head which is clamped to the vertical column may be swiveled at an angle, permitting the milling cutter mounted on the spindle to work on angular surfaces. In some machines, the spindle can also be adjusted up or down ‘relative to the work. •The machine is adapted. for machining grooves, slots, and flat surfaces. The end mills and face milling cutters are the usual tools mounted on the spindle. PARTS OF A MILLING MACHINE BASE: The base of the machine is a grey iron casting accurately machined on its top and bottom surface and serves as a foundation member for all the other parts which rest upon it. COLUMN: The column is the main supporting frame mounted vertically on the base. The column is box shaped, heavily ribbed inside and houses all the driving mechanisms for the spindle and table feed. KNEE: The knee is a rigid grey iron casting that slides up and down on the vertical ways of the column face. The adjustment of height is effected by an elevating screw mounted on the base that also supports the knee TABLE: The table rests on ways on the saddle and travels longitudinally. The top of the table is accurately finished and T-slots arc provided for clamping the work and other fixtures on it. . OVERHANGINGARM: The overhanging arm that is mounted on the top of the column extends beyond the column face and serves as a bearing support for the other end of the arbor. FRONT BRACE: The front brace is an extra support that is fitted between the knee and the over arm to ensure further rigidity to the arbor and the kneel the front brace is slotted to allow for the adjustment of the height of the knee relative to the over arm. MILLINGMACHINE MECHANISM •The milling machine mechanism is composed of spindle drive mechanism and the table feed mechanism.

•The spindle drive mechanism is incorporated in the column. •All modem machines are driven by individual motors housed within the column, and the spindle receives power from a combination of gears and clutch assembly. •Multiple speed of the spindle may be obtained by altering the gear ratio. •The power feed mechanism contained within the knee of the machine to enable the table to have three different feed movements, longitudinal, cross, and vertical. •The power is transmitted form the feed gear box consisting of change gears to shaft in the knee of the machine by a telescopic shaft SIZEOF MILLING MACHINE Table length x width = 1100mm x 310 mm. Power traverse: longitudinal x cross x vertical=650mmx235mmX420mm. MILLING CUTTERS •The milling cutters are revolving tools having one or several cutting edges of identical form equally spaced on the circumference of the cutter. •The cutting elements are called a tooth which intermittently engages the work piece and remove material by relative movement of the work piece and cutter. Milling cutters may be classified as: 1. According to the constructional features of the cutter: Solid cutter. Tipped solid cutter. Inserted teeth cutter. 2. According to the relief characteristics of the cutter teeth: Profile relieved cutter Form relieved cutter 3. According to the methods of mounting the cutter: Arbor type cutter. Shank type cutter. Facing type cutter.  

4. According to the direction of rotation of the cutter: •Right hand rotational cutter. •Left hand rotational cutter  

5. According to the direction of helix of the cutter teeth:  Parallel or straight teeth cutter.

Right hand helical cutter. Left hand helical cutter. Alternate helical teeth cutter. 6. According to purpose or use of the cutter: Standard milling cutter. Special milling cutter. Solid cutter: A solid cutter has teeth integral with the cutter body. The cutters are of smaller diameter and width and made of one piece material usually of high speed steel. Tipped solid cutter: A tipped solid cutter is similar to a solid cutter; expect that the cutter teeth are made of cemented carbide or stellite tips which are brazed on the tool shanks of an ordinary tool steel cutter body to reduce the cost of the cutter. Inserted teeth cutter: In large milling cutters, the teeth or blades are inserted or secured in a body of less expensive materials. The blades are usually held in the cutter body by mechanical means. The arrangement reduces the cost of the cutter and enables economy in maintenance, as a single tooth if broken can be readily replaced. Profile relieved cutter: In this category of milling cutters, a relief to the cutting edges is provided by grinding a narrow land at the back of the cutting edges. The profile relieved cutters generate fiat, curved or irregular surfaces Form relieved cutter: In this category of milling cutters a curved relief is provided at the back of the cutting edges. The cutters are sharpened by grinding the faces of the teeth. The form relieved cutters are mainly used for generating formed or contoured surfaces. Arbor type cutter: The arbor type cutters are provided with a central hole having a keyway for mounting them directly on the milling machine arbor. Milling cutters having tapered or threaded holes are also available. They are mounted on arbors of different designs. Shank type cutter:

The shank type cutters are provided with straight or tapered shank integral with the cutter body. The straight or tapered shanks are inserted into the spindle nose and are clamped to it either by friction or by a draw bolt. Facing type cutter: The facing type cutters are either bolted or attached directly to the spindle nose, or secured on the face of a short arbor called stud arbor. The facing type cutters are mainly used to produce fiat surfaces. Right hand cutter: A milling cutter is designated as a right hand cutter which rotates in an anticlockwise direction when viewed from the end of the spindle. There are many different types of standard milling cutters. They are classified below 1. Plain milling cutter.

Light duty plain milling cutter. Heavy duty plain milling cutter. Helical plain milling cutter.

2. Side milling cutter.

Plain side milling cutter. Staggered teeth side milling cutter. Half side milling cutter. Interlocking side milling cutter.

3. Metal slitting saw

Plain metal slitting saw. Staggered teeth metal slitting saw.

4. Angle milling cutter

Single angle milling cutter. Double angle milling cutter.

5. End mill. Taper shank end mill. Straightshank end mill. Shell end mill.

6. T-slot milling cutter. 7. Woodruff key slot milling cutter. 8. Fly cutter. 9. Formed cutter

Convex milling cutter. Concave milling cutter. Corner rounding milling cutter. Gear cutter

Thread milling cutter. 10. Tap and reamer cutter.

MILLING CUTTER MATERIAL The milling cutters may be made of high speed steel, super high speed steel, non-ferrous cast alloys or cemented carbide tipped. The high speed steel cutters are the most widely used cutters in general shop work. The cutters are successfully used for plain milling or slotting operations where the chip thickness is small. FUNDAMENTALS OF THE MILLING PROCESSES PERIPHERALMILLING: The peripheral milling is the operations performed by a milling cutter to produce a machined surface parallel to the axis of rotation of the cutter. In peripheral milling the cutting force is not uniform throughout the length of the cut by each tooth. UPMILLING DOWN MILLING

FACE MILLING: The face milling is the operation performed by a milling cutter to produce a flat machine surface perpendicular to the axis of rotation of the cutter. The peripheral cutting edges of the cutter do the actual cutting, whereas the face cutting edges finish up the work surface by removing a very small amount of material. END MILLING: The end milling may lie considered as the combination of peripheral and face milling operation. The cutter has teeth both on the end face and on the periphery. The cutting characteristics may be of peripheral or face milling type according to the particular cutter surface used. CUTTINGSPEED AND FEED C u t t i n g s p e e d : The speed of milling cutter is its peripheral linear speed resulting from rotation. It is expressed in meters per minute. Feed: The feed in a milling machine is defined as the rate with which the work piece advances under the cutter. The feed is expressed in a milling machine by the following three different methods. DRILLING MACHINE TYPES OF DRILLING MACHINE Drilling machines are made in many different types and sizes, each designed to handle a class of work or specific job to the best advantage. The different types of drilling machines are Portable drilling machine. Sensitive drilling machine. (a) Bench mounting,

Upright drilling machine. (a) Round column section, Radial drilling machine. (a) Plain (c) Universal Gang drilling machine. Multiple spindle drilling machine. Automatic drilling machine. Deep hole drilling machine. FEEDMECHANISM: In a drilling machine, the feed is affected by the vertical movement of the drill into the work. The feed movement of the drill may be controlled by hand or power. The hand feed may be applied by two methods: Quick traverse hand feed Sensitive hand feed RADIAL DRILLNG MACHINE PARTS The different parts of a radial drilling machine are follows: Base Drill head Column Spindle speed and feed mechanism Radial arm WORK HOLDING DEVICES The devices commonly used for holding the work in a drilling machine are T-bolt and clamps. Drill press vise. Step blocky V-block. Angle plate. Drill jigs DRILLING MACHINE OPERATIONS The different operations that can be performed in a drilling machine are: Drilling. Spot facing. Reaming. Tapping. Boring

Lapping. Counter boring. Grinding. Countersinking. Trepanning. DRILLING: Drilling is the operation of producing a cylindrical hole by removing metal by the rotating edge of a cutting tool called the drill. The drilling is one of the simplest methods of producing a hole. Before drilling the centre of the hole is located on the work piece by drawing two lines at right angles to each other and then a centre punch is used to produce an indentation at the center. REAMING: Reaming is an accurate way of sizing and finishing a hole which has previously drilled. In order to finish a hole and to bring it to the accurate size, the hole is drilled slightly undersize. The speed of the spindle is made half that of drilling and automatic feed may be employed the tool used for reaming is known as the reamer which has multiple cutting edges.

BORING: Boring is performed in a drilling machine for reasons stated below To enlarge a hole by means of an adjustable cutting tool with only one cutting edge. To finish a hole accurately and to bring it to the required size. To machine the internal surface of a hole already produced in casting. To correct out of roundness of the hole. To correct the location of the hole as the boring tool follows an independent path with respect to the hole. LAPPING: Lapping is the operation of sizing and finishing a small diameter hole already hardened by removing a very small amount of material by using a lap. GRINDING: Grinding operation may be performed in a drilling machine to finish a hardened hole. The grinding wheel is made to revolve with the spindle and is fed up and down. TREPANNING: It is the operation of producing a hole by removing metal along the circumference of a hollow cutting tool. Trepanning operation is performed for producing large holes. DRILL MATERIAL The materials for the manufacture of twist drills are as follows

One piece construction: High speed steel or carbon steel. Two piece construction: Cutting portion—high speed steel. Shank portion—Carbon steel with a minimum tensile strength of 70 kg per sq mm. REAMER A reamer is a tool used for enlarging or finishing a hole previously drilled, bored or cored to give a good finish and an accurate dimension. A reamer is a multi-tooth cutter which removes relatively small amount of material. Chucking reamer with parallel or taper shank (a) Fluted reamer, (b) Rose reamer Machine bridge reamer Machine jig reamer Parallel hand reamer with parallel shank Parallel or taper shank socket head reamer

BORING MACHINES The boring machine is one of the most versatile machine tools used to bore holes in large and heavy parts such as engine frames, steam engine cylinders, machine housings, Which are practically impossible to hold and rotate in an engine lathe or a drilling machine. TYPESOF BORINGMACHINES The boring machines may be classified under the four headings: Horizontal boring machine. Table type. Floor type. Planer type. Multiple head type Vertical boring machine. Vertical turret lathe. Standard vertical boring machine. Precision boring machine. Jig boring machine Vertical milling machine type. Planer type. BORING MACHINE MECHANISM The machine contains different controls for movements of the different parts of the machine. A table type machine has the following movements: The headstock and the end supporting block may be moved up and down. The spindle may be rotated. The spindle has different speeds. The spindle may be, moved in or out by hand or power for feeding. The saddle and the table may be moved by hand or power. The columns may be moved by hand or power. TAPPING

TAPS:

A tap is a screw-like tool which has threads like a bolt and three or four flutes cut across the thread. It is used to cut threads on the inside of a hole, as in a nut.

The edges of the thread formed by the flutes are the cutting edges. The lower part of the tap is somewhat tapered so that it can into the walls of the drilled hole.

The upper part of the tap consists of a shank ending in a square for holding the tap in the machine spindle or by a tap wrench.

Taps are made from carbon steel or high speed steel and are hardened and tempered. Taps are classified as ( 1 ) H a n d t a p (2)Machine tap HAND TAP:

The hand taps illustrated are usually made in sets of three:

Taper tap Second tap Bottoming tap M a c h i n e t a p :

Machine taps have straight or helical flutes. In machine tapping it is necessary to see that the chips always clear the cutting edges.