Module - 4 - Shaper, Planer, Slotter, Grinding Machines

7/27/2019 Module - 4 - Shaper, Planer, Slotter, Grinding Machines

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Drilling Machines: Types of machines, Types of drillings,operations such as drilling, boring, reaming, spot facing,counter boring, counter sinking and tapping. Drill speedsand feeds.

Plaining machines, shaping machines and slotting

machine: Various types, construction and working,operations and tools, field of application, quick returnmechanism and feed mechanisms of these machines.

Grinding: Grinding machines such as pedestal,

cylindrical surface, centre less and tool and cuttergrinder. Operations on the above mentioned machines.Grinding wheel, selection and specifications. Dressingand truing of grinding wheels. Finishing operations suchas lapping and honing.

8/30/2012 2Prof. Irfan Shaikh


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Definition of Shaping, Planing &

Slotting Machine Planing, shaping, and slotting are processes for machining

horizontal, vertical, and inclined flat surfaces, slots, orgrooves by means of a lathe-type cutting tool.

In all these processes, the cutting action takes place along a

straight line. In planing, the workpiece (and the machinebed) is reciprocated, and the tool is fed across theworkpiece to reproduce another straight line, thusgenerating a flat surface.

In shaping and slotting, the cutting tool is reciprocated, and

the workpiece is fed normal to the direction of tool motion.The difference between the latter two processes is that thetool path is horizontal in shaping and it is vertical inslotting.

Shapers and Slotters can be employed in cutting external

and internal keyways, gear racks, dovetails, and T-slots.8/30/2012 3Prof. Irfan Shaikh


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Planing and Shaping Tools

Planing and shaping processes employ single-pointtools of the lathe type, but heavier in construction.

They are made of either high-speed steel or carbontool steel with carbide tips. In the latter case, themachine tool should be equipped with an automatic

lifting device to keep the tool from rubbing theworkpiece during the return stroke, thus eliminatingthe possibility of breaking or chipping the carbide tips.

The cutting angles for these tools depend upon thepurpose for which the tool is to be used and thematerial being cut. The end relief angle does notusually exceed 4, whereas the side relief variesbetween 6 and 14. The side rake angle also variesbetween 5 (for cast iron) and 15 (for medium-carbonsteel).



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Job surfaces generated by shaper



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Shaping process & MRR



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Machine arrangement for shaping



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Principal parts of shaper1. Base

2. Column3. Cross-rail

4. Saddle

5. Table

6. Ram

7. Tool head8. Clapper box

9. Apron clamping bolt

10. Down feed hand wheel

11. Swivel base degree graduations

12. Position of stroke adjustment hand wheel13. Ram block locking handle

14. Driving pulley

15. Feed disc

16. Pawl mechanism

17. Elevating screw8/30/2012 9Prof. Irfan Shaikh


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Horizontal Push-Cut Shaper



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Details and working principles of the

quick return mechanism

Quick return mechanism



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Cutting action and functioning of

clapper box



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Vertical Shaper

The vertical shaper is similar in construction andoperation to the push-cut shaper, the difference beingthat the ram and the tool head travel vertically insteadof horizontally.

Also, in this type of shaper, the workpiece is mountedon a round table that can have a rotary feed wheneverdesired to allow the machining of curved surfaces (e.g.,spiral grooves).

Vertical shapers, which are sometimes referred to as

slotters, are used in internal cutting. Another type of vertical shaper is known as a keyseater

because it is specially designed for cutting keyways ingears, cams, pulleys, and the like.



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Surfaces produced on shaper

1. Horizontal plain surface

2. Vertical plain surface

3. Inclined surface4. Grooved surface

5. Slotted surface

6. Stepped surface



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Machining horizontal & vertical surface

on shaper



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Machining angular surface on shaper



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Slotting & Keyway machining on

shaper



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Planer A planer is a machine tool that does the same work as the

horizontal shaper but on workpieces that are much larger thanthose machined on a shaper.

Double-housing and Open-side constructions.

In a double-housing planer, two vertical housings are mounted atthe sides of the long, heavy bed.

A cross rail that is supported at the top of these housings carries

the cutting tools. The machine table (while in operation) reciprocates along the

guideways of the bed and has T-slots in its upper surface forclamping the workpiece.

In this type of planer, the table is powered by a variable-speed dc

motor through a gear drive. The cross rail can be raised or lowered as required, and the

inclination of the tools can be adjusted as well.

In an open-side planer, there is only one upright housing at one sideof the bed. This construction provides more flexibility when widerworkpieces are to be machined.



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Machine arrangement for planing



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8/30/2012 Prof. Irfan Shaikh 21


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Drilling is an operation of making a circular hole byremoving a volume of metal from the job by cutting toolcalled drill.

A drill is a rotary end-cutting tool with one or more cuttinglips and usually one or more flutes for the passage of chipsand the admission of cutting fluid.

A drilling machine is a machine tool designed for drillingholes in metals.

It is one of the most important and versatile machine tools

in a workshop. Besides drilling round holes, many otheroperations can also be performed on the drilling machinesuch as counter- boring,countersinking, honing, reaming,lapping, sanding etc.



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Construction of Drilling machine



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Types of Drilling machine(1) Portable drilling machine

(2) Sensitive drilling machine

(a) Bench mounting

(b) Floor mounting

(3) Upright drilling machine

(a) Round column section(b) Box column section machine

(4) Radial drilling machine

(a) Plain

(b) Semi universal

(c) Universal(5) Gang drilling machine

(6) Multiple spindle drilling machine

(7) Automatic drilling machine

(8) Deep hole drilling machine



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Portable Drilling Machine

A portable drilling machine is a small compact unit andused for drilling holes in workpieces in any position,which cannot be drilled in a standard drilling machine.

It may be used for drilling small diameter holes in largecastings or weldments at that place itself where theyare lying.

Portable drilling machines are fitted with small electricmotors, which may be driven by both A.C. and D.C.

power supply.

These drilling machines operate at fairly high speedsand accommodate drills up to 12 mm in diameter.



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Sensitive Drilling Machine It is a small machine used for drilling small holes in

light jobs. In this drilling machine, the workpiece ismounted on the table and drill is fed into the work bypurely hand control.

High rotating speed of the drill and hand feed are the

major features of sensitive drilling machine. As theoperator senses the drilling action in the workpiece, atany instant, it is called sensitive drilling machine.

A sensitive drilling machine consists of a horizontaltable, a vertical column, a head supporting the motor

and driving mechanism, and a vertical spindle. Drills of diameter from 1.5 to 15.5 mm can be rotated

in the spindle of sensitive drilling



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Upright Drilling Machine

The upright drilling machine is larger and heavier thana sensitive drilling machine.

It is designed for handling medium sized workpiecesand is supplied with power feed arrangement.

In this machine a large number of spindle speeds andfeeds may be available for drilling different types ofwork.

Upright drilling machines are available in various sizesand with various drilling capacities (ranging up to 75mm diameter drills).

The table of the machine also has different types ofadjustments.



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Radial Drilling Machine The radial drilling machine consists of a heavy, round vertical column

supporting a horizontal arm that carries the drill head. Arm can be raised or lowered on the column and can also be swung

around to any position over the work and can be locked in any position.

The drill head containing mechanism for rotating and feeding the drill ismounted on a radial arm and can be moved horizontally on the guide-ways and clamped at any desired position.

These adjustments of arm and drilling head permit the operator to locatethe drill quickly over any point on the work. The table of radial drillingmachine may also be rotated through 360 deg.

The maximum size of hole that the machine can drill is not more than 50mm.

Powerful drive motors are geared directly into the head of the machine

and a wide range of power feeds are available as well as sensitive andgeared manual feeds.

The radial drilling machine is used primarily for drilling medium to largeand heavy workpieces.



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Construction of Radial Drilling Machine



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Gang Drilling Machine

In gang drilling machine, a number of singlespindle drilling machine columns are placedside by side on a common base and have a

common worktable. A series of operation may be performed on

the job by shifting the work from one positionto the other on the worktable.

This type of machine is mainly used forproduction work.



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Multiple-Spindle Drilling Machine

The multiple-spindle drilling machine is usedto drill a number of holes in a jobsimultaneously and to reproduce the same

pattern of holes in a number of identicalpieces in a mass production work.

This machine has several spindles and all thespindles holding drills are fed into the work

simultaneously. Feeding motion is usuallyobtained by raising the worktable.



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Types of drills

A drill is a multi point cutting tool used to

produce or enlarge a hole in the workpiece.

It usually consists of two cutting edges set an

angle with the axis. Broadly there are three

types of drills:

1. Flat drill,

2. Straight-fluted drill, and

3. Twist drill



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Twist drill Two cutting edges and two

helical flutes The two cutting edges are

referred to as the lips andare connected together bya wedge, which is a chisel-like edge.

Two margins that allow thedrill to be properly located

and guided while it is inoperation.

The tool point angle (TPA)The usual TPA forcommercial drills is 118,which is appropriate fordrilling low-carbon steelsand cast irons.

For harder and toughermetals, such as hardenedsteel, brass, and bronze,larger TPAs (130 or 140)give better performance.



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The helix angle of the flutes of a twist drill rangesbetween 24 and 30.

When drilling copper or soft plastics, higher

values for the helix angle are recommended(between 35 and 45).

Twist drills are usually made of high-speed steel,although carbide-tipped drills are also available.

The sizes of twist drills used in industrial practicerange from 0.01 inch to 31/2 inches (0.25 up to 80mm).


Twist drill


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Operations performed on drilling

machine

A drill machine is versatile machine tool. Anumber of operations can be performed on it.Some of the operations that can be performed ondrilling machines are:

1. Drilling 2. Reaming

3. Boring 4. Counter boring

5. Countersinking 6. Spot facing

7. Tapping 8. Lapping

9. Grinding 10. Trepanning.



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Reaming

This is the operation ofsizing and finishing a holealready made by a drill.Reaming is performed bymeans of a cutting toolcalled reamer as shown inFig.

Reaming operation servesto make the hole smooth,straight and accurate indiameter. Reamingoperation is performed bymeans of a multitoothtool called reamer.



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Boring

Fig. shows the boring

operation where

enlarging a hole by means

of adjustable cutting toolswith only one cutting

edge is accomplished. A

boring tool is employedfor this purpose.



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Counter-Boring

Counter boring

operation is shown in

Fig. It is the operation

of enlarging the end ofa hole cylindrically, as

for the recess for a

counter-sunk rivet. Thetool used is known as

counter-bore.



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Counter-Sinking

This is the operation ofmaking a cone shapedenlargement of the end of ahole, as for the recess for a

flat head screw. This is done for providing a

seat for counter sunk headsof the screws so that the

latter may flush with themain surface of the work.



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Spot-Facing

This is the operationof removing enoughmaterial to provide aflat surface around ahole to accommodatethe head of a bolt or anut.

A spot-facing tool isvery nearly similar tothe counter-bore



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Tapping

It is the operation of cuttinginternal threads by using a toolcalled a tap.

A tap is similar to a bolt withaccurate threads cut on it.

To perform the tappingoperation, a tap is screwed intothe hole by hand or by machine.

The tap removes metal and cuts

internal threads, which will fitinto external threads of thesame size.



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Cutting speed

The cutting speed in a drilling operation refers

to the peripheral speed of a point on the

surface of the drill in contact with the work. It

is usually expressed in meters/min.

The cutting speed (Cs) may be calculated as:



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Feed

The feed of a drill is the distance the drill movesinto the job at each revolution of the spindle.

It is expressed in millimeter. The feed may also beexpressed as feed per minute.

The feed per minute may be defined as the axialdistance moved by the drill into the work perminute. The feed per minute may be calculatedas:



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Grinding operations

Grinding is a manufacturing process that involves theremoval of metal by employing a rotating abrasivewheel.

The wheel simulates a milling cutter with an extremely

large number of miniature cutting edges.

Generally, grinding is considered to be a finishingprocess and is used for obtaining high-dimensionalaccuracy and superior surface finish.

Grinding can be performed on flat, cylindrical, or eveninternal surfaces by employing specialized machinetools, referred to as grinding machines.



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Types of Grinding Operations

Surface grinding.



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Cylindrical grinding


Types of Grinding Operations


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M hi i Ti d MRR f


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Machining Time and MRR for

Cylindrical Grinding


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Internal grinding

Internal grinding isemployed for grindingrelatively short holes, asshown in Figure.

The workpiece is held ina chuck or a specialfixture. Both thegrinding wheel and theworkpiece rotate duringthe operation, and feedis applied in the

longitudinal direction. Any desired depth of cut

can be obtained by thecross feed of thegrinding wheel.



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Centerless grinding Centerless grinding involves passing a cylindrical workpiece,

which is supported by a rest blade, between two wheels(i.e., the grinding wheel and the regulating or feed wheel).

The grinding wheel does the actual grinding, while theregulating wheel is responsible for rotating the workpieceas well as generating the longitudinal feed.

This is possible because of the frictional characteristics ofthis wheel, which is usually made of rubber-bondedabrasive.

The velocity of the regulating wheel is controllable and is

used to achieve any desired rotational speed of theworkpiece. The angle a is usually taken from 1 to 5; thelarger the angle, the larger the longitudinal feed will be.



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Centerless grinding


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Grinding Wheels

Grinding wheels are composed of abrasive grains havingsimilar size and a binder.

The actual grinding process is performed by the abrasivegrains. Pores between the grains within the binder enablethe grains to act like separate single-point cutting tools.

These pores also provide space for the generated chips,thus preventing the wheel from clogging.

In addition, pores assist the easy flow of coolants so thatheat generated during the grinding process is efficientlyand promptly removed.

Grinding wheels are identified by their shape and size, kindof abrasive, grain size, binder, grade (hardness), andstructure.



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Grinding process parameters

The process of grinding is dependent upon the

following:.

a. Type of abrasive used in the wheel

b. Size and distribution of grit in the wheel

c. Amount and type of bonding material

d. Volume of porosity: relative to abrasive andbonding material.



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Shape and size of grinding wheels.

Straight wheels for surface, cylindrical, internal,and centerless grinding

Beveled-face or tapered wheels for grindingthreads, gear teeth, and the like.

Straight recessed wheels for cylindrical grindingand facing

Abrasive disks for cutoff and slotting operationswhen thickness is 0.02 to 0.2 inch (0.5 to 5 mm)

Cylindrical, straight, and flaring cups for surfacegrinding with the end of the wheel



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Various shapes of grinding wheels



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Abrasive Material Natural abrasives: Natural abrasives include sand

stone, diamond, corundum and emery. Diamondabrasive wheels are used sharpening carbide andceramic cutting tools.

They are also used for turning and dressing other types

of abrasive wheels. Artificial abrasives: They include silicon carbide and

aluminum oxide. Silicon carbide is made by heatingsilica sand, coke, salt and sawdust in an electric furnaceat 23000oC for hours resulting in a solid mass of silicon

carbide. Upon cooling, this mass is removed from the furnace,

crushed and graded as per the various sizes obtained.



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Abrasive Grain Size

Abrasive materials are crushed in ball mills andsegregated as per size. The selection of size of theabrasive grain required depends upon thefollowing factors:

1. Amount of material to be removed2. Finish desired

3. Hardness of material being ground

The coarse grit is used for more material removalwhere as the fine grit is used for small materialremoval rate. Sizes from 240 to 600 are used forlapping and honing applications.



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Bonding materials

Bonding materials are used to hold the abrasiveparticles in place. There are six types of bondingmaterial used. They are:

Bonds Symbol

Vitrified Bonds VResinoid Bonds B

Shellac Bonds E

Rubber Bonds RSilicate Bonds S

Oxy-chloride Bonds O



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Structure

It is the spacing between the abrasive gains or

the density of the wheel. The structure of the

grinding wheel is designated by a number. The

higher the number, the wider is the spacing.Structure Symbol

Dense 1 2 3 4 5 6 7 8

Open 9 10 11 12 13 14 15 or more



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Specifications of A Grinding Wheel



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Cutting fluids

The various cutting fluids generally used are as

follows:

One per cent solution of soda ash with 0.15 per

cent sodium nitrite. A two percent water solution of powdered soap.

Cast iron and copper are ground without any

coolant. Aluminum is ground by using kerosenewith or without a mixture of mineral oil as a

coolant.



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Operation Performed on GrindingMachine



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Polishing

This process is used for removing scratch

marks and tool marks on the work piece to

give a good look.

For this process, polishing wheels made ofcanvas, leather or paper are used. The work

piece is brought in contact with the revolving

wheel to remove the marks on the work piece.



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Buffing

This is also a surface finishing process and is

used to produce lustrous surface of attractive

appearance. In this process, a very small

amount of material is removed. The buffing wheel is made of felt, cotton and

powered abrasives are applied on the surface

of the wheel.



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Lapping

This process is used for producing extremely accuratehighly finished surfaces.

Lapping is carried out by means of shoes called Laps. TheLaps are made up of soft cast iron, copper, lead and brass.Fine abrasive particles are charged into the lap.

Silicon carbide, aluminum oxide and diamond dust are thecommonly used lapping powders.

Oil and greases are used to spread the abrasive powders.The charged lap is rubbed against the work piece surfaceand the abrasive particles in the surface of the lap removesmall amounts of material from the work piece surface. Thematerial removed by lapping is usually less than 0.025 mm.



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Honing

Honing is an abrasing process used for finishinginternal cylindrical surfaces like drilled or boredholes. Honing stones are manufactured bybonding abrasives like aluminum oxide or siliconcarbide. Materials like sulphur, resin or wax areadded to improve the cutting action.

Honing is both a sizing and finishing operation

and is generally used for removing the scratchmarks produced by grinding. The materialremoval is less than 0.125 mm.



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Documents

Module - 4 - Shaper, Planer, Slotter, Grinding Machines