lathe drilling

8/10/2019 Lathe Drilling

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Elements of Mechanical Engineering.

Unit 5: Lathe and Drilling Machines.

Cutting tools :- Tools which are used to separate/remove material stock from the work piece areknown as cutting tools. Ex hack saw, chisel etc.

Machine tools : - Machine tools are power driven cutting tools or machines which enable theremoval of excess stock of material from the work piece.

Relative Motion : - change in position of a ob ect ! fixed/moving" with respect to the other ob ect!fixed/moving"is called as relative motion.

#athe:- #athe is one of the most widel$ used machine tools in metal cutting work.

#athe is usuall$ used for machining !metal removal" the ob which is rotated and a cuttingtool is fed to cause the cutting action.

#athe is generall$ used for machining c$lindrical obs.

Working principle of Lathe

The work piece is hold firml$ in the work holding device called the chuck and is supported b$ thedead center as shown in the fig.aboveThe chuck is rotated at a particular speed b$ some mechanisms% the cutting tool is moved against therotating work piece to facilitate the removal of material.

&ept. of Mechanical Engineering, 'rinivas 'chool of Engineering, Mangalore.

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chematic diagram of Lathe Machine.

!. "ed: The lathe bed provides a heav$ rigid frame on which all the main components likeheadstock, tail stock and carriage are mounted. (t comprises inner and outer guide rails that are

precision machined. bed is made out of cast iron allo$.

#. $eadstock: (t is mounted in a fixed position at the left end on the bed. (t carries a hollow spindlewhich can rotate at different speeds.The spindle carries a work-holding device which in turn rotates the ob to be machined. The spindlespeed is controlled b$ a stepped cone pulle$ and back gear arrangement both of which are housed inside the headstock.

%. &ailstock: (t is mounted at the left end on the bed and can slide towards the headstock. (t can befixed at an$ position on the bed to suit the length of the work to hold a lathe center, drill bit or othersuch tool. The tailstock is used for drilling,reaming, tapping, threading and centering parts.

'. Carriage: (t moves on the guide wa$s of the lathe bed. ) cutting tool is fixed in the tool post, themovement of which is guided b$ the carriage. The carriage is e*uipped with levers, clutches andgears that control its movement either b$ hand or b$ power feed. (t carries the followingunits.( addle: (t is the main part or the base of the carriage which slides along the bed wa$s. (t supportscross-slide, compound rest and tool post. +enerall$, it uses a hand wheel to move along the bed but itcan also be power operated through the apron mechanism.

( Cross slide: (t is mounted on the saddle and slides in a direction perpendicular to the axis of thespindle( Compound rest: (t is mounted on the top of the cross-slide. (t can swivel to an$ desired



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angle in a hori ontal plane. (t is operated b$ a handwheel through the compound rest..Tool post: It is fixed on top of the compound rest and mounts the tool holder, in which the cutting tools are clamped.. Apron is attached to the front of the carriage and bears the mechanism which controls the

movement of the carriage and the cross slide.

. Legs: The whole machine is supported on two legs made out of cast iron. The leg on left sidehouses the electric motor and the headstock, the right side leg houses tailstock and other parts.

Lathe Operations

The lathe is the most versatile general-purpose machine tool. (t is capable to perform a large variet$of operations . ollowing are a few operations that can be performed on a lathe:

. Turning: Turning is a lathe operation in which the cutting tool removes metal from the outsidediameter of a workpiece. (n other words, reduction in the diameter of the workpiece is called turning.&epending upon the ob re*uirement, the turning operation ma$ be of various t$pessuch asa. 'traight turning

b.'tepped turningc.Taper turningd. ontour turning.

0. acing: acing is the process of removing metal from the end of a workpiece to produce a flatsurface.(n other words a reduction in length of the workpiece is called facing. The cutting tool is fed into theworkpiece in a direction perpendicular to its axis

a. traight &urning b. tep &urning



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&aper &urning )nurling

*rooving Chamfering &hread cutting

Drilling "oring

+arting ,ff: (t uses a cutting tool to cut-off the workpiece at a specific length.. (t is normall$ usedto remove the finished end of a workpiece from the bar stock!raw material" that is clamped in thechuck.

*rooving: (t is an operation of reducing diameter of the workpiece in the form of a neck or a narrowgroove of desired shape, ma$ be a round, a s*uare or a 1 shape.

Chamfering: (t is a process of cutting the sharp edge at the end of a ob to produce a beveled edge ata desired angle.



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Drilling: (t is a lathe operation b$ which an axial hole is created in a solid workpiece. (t is done withthe help of a special multi-point tool called a drill.

Reaming: (t is an operation b$ which the surface of a drilled hole is finished. (t is done with the helpof a special multi-point tool called a reamer.feed !2.3-0 mm ".

"oring: (t is an operation b$ which a drilled hole is enlarged in diameter. (t is done with the help of asingle-point cutting tool called a boring bar.

)nurling: (t is a special operation b$ which a smooth-turned surface is made rough b$ impressing adiamond shaped or straight line pattern. (t is done for the purpose of creating a better gripping.surface. 4nurling is performed with special metal wheels called a knurling tool.

&hread Cutting: (t is a process of cutting helical grooves of a standard thread form. (t ma$ be of two t$pes, namel$, external thread cutting and internal thread cutting.

!tapping,taperboring,undercutting,milling,counterboring,grooving,filling,polishing,spinning,springwinding5 forming"

&aper &urning

Taper turning is the process of generating a conical surface.Taper turning on a lathe is done b$ feeding the cutting tool at an angle to the axis of rotation theworkpiece. ) taper is a uniform increase or decrease in the diameter of the workpiece along its length.

There are four basic methods of turning tapers on a lathe:6 b$ form tool%6 b$ compound rest swivel%6 b$ tailstock set-over%

6 b$ taper turning attachment.

Determination of angle of taper :onsider a c$lindrical workpiece of length # and diameter &.as shown in fig below (t is re*uired to

reduce the diameter & to d uniforml$ over the length #. The amount of taper in the workpiece isusuall$ specified as conicity. (t is denoted b$ letter 4.



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7here &- dia at the larger end, d-dia at the smaller end, #8 length of workpiece

&aper &urning b- iveling the Compound Rest

9The work piece is rotated on lathe axis .The cutting tool mounted on the compound rest is attachedto a circular base which can be swiveled and locked at an$ desired taper angle as shown in ig.9 ompound rest ma$ be swiveled at either side of the lathe. 7hen the compound rest set at thedesired taper angle is moved against the workpiece the cutting tool generatesthe re*uired tapered surface on the workpiece.9)s the compound tool rest has onl$ limited movement, this method can generate onl$ shorttapers.



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&aper &urning b- &aper &urning /ttachment

9 ere a taper attachment which is set at an angle to the axis of rotation of the workpiece. guide thetool in a straight path to cut both internal and external tapers as shown in ig. >The workpiece held

between the centers and is aligned to the lathe axis.9The attachment consists of bracket or frame connected to the rear end of the lathe bed.) guide bar having graduations in degrees ma$ be swiveled either side of the ero.+raduation on a pivot mounted over the bracket as shown in fig.The cross slide is made free from lead screw and its rear end is attached to the guide block b$ meansof a bolt.7hen the longitudinal feed is given b$ moving the carriage, the guide block slides over guide bar set

at half the taper angle. The tool mounted on the cross slide follows the angular path and generates there*uired taper.



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&aper &urning b- &ailstock et0over

ere the workpiece is held between the live center and the dead center of the tailstock. ;ut thetailstock is offset at an angle e*ual to half the taper angle as shown in ig. The cutting tool is fed parallel to the lathe axis. )nd the desired taper is produced.

&aper &urning b- a 1orm &ool

9 ere a taper tool of broad nose having straight cutting edge is used to produce the desired taper as shown in ig. 9since this method produces taper onl$ for short length it is not widel$ used.



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pecification of Lathe:

) lathe is mainl$ specified b$ the maximum si e of the work that it can handle.. range of spindle speeds%3. range of feeds%?. space occupied b$ the machine



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Drilling is an operation of producing holes in a solid metal2non metals b- means of a revolvingtool called drill or t ist drill.The machines emplo$ed for drilling holes are called drilling machines. The drilling machine .&rillingmachine is the one of the essential machine tool used in fabrication, production shop and tool rooms,

for machining/producing holes.The machine consists of a spindle which provides rotar$ motion to the drilling tool!twist". Thespindle ma$ also produce motion to table on which the work rests.

TYPES OF DRILLING MACHINES

&rilling machines are manufactured in various si es and varieties to suit different t$peswork. The$ are classified as follows.l" @ortable drilling machine0" 'ensitive or bench drilling machine=" Ap-right drilling machine

>" Badial drilling machine3" +ang drilling machine?" Multiple-spindle drilling machineC" &eep-hole drilling machine

+ortable Drilling Machine: (t is small drilling machine designed to drill small holes up to D mm diameter. The machine can becarried to the obs which normall$ cannot be brought to the workshop, such as concrete sellingslabs,walls,heav$ machiner$, and fabrication sites.

(t is ver$ light in weight and can be convenientl$ handled. ig above shows a portable hand helddrilling machine.



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Upright2+illar Drilling Machine

This machine is *uite similar to the bench drilling machine but of little larger si e and higher capacit$ and is fixed on the floor foundation. This drilling machine is able to take larger drills.



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Radial Drilling Machine:

The machine consists of a vertical column mounted on a large base. (t supports a radial arm which can swing about the column axis and move verticall$ up and down.The radial arm carries a drill head which can slide in its guidewa$s and clamped at the desired

position. ) motor is mounted on the drill head to rotate the drill spindle. ) feed lever on the drill headguides the feed motion.

) combination of these movements helps to locate the drill at an$ desired position. This t$pe of drilling machine is used in tool rooms and in large scale manufacturing units.

,ther drillings machines. &eephole drilling machines0. Aniversal drilling machines=. +ang drilling machines>. Multispindle drilling machine3. H drilling machines.



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tool is lesser than the speed of rotation of a corresponding reamer. oles with accurac$ of 2.22 03mm can be obtained b$ this operation.

Counter0"oring

(t is a special operation performed on drilling machine for enlarging a limited portion of the hole.The bottom surface of the enlarged hole is flat. (t is generall$ used when a bolt or cap head screw or a nut is re*uired to sit below the level of a workpieceFs surface.

ounter-boring is done with the help of a special tool called a counter-bore. The counter-bore isguided in drilled hole with the help of a pilot fixed at its lower end.

Counter0 inking :I

(t is a process of making a conical hole to a limited depth at the entrance to c$lindrical hole. )counter-sunk hole allows sitting the conical head of a bolt or a screw below surface of the workpiece.(t is cut with the help of a tool called a counter-sinking tool.

ounter sink cutters are manufactured with six common included angles which are ?2J, D0J, K2J,22, 2J or 02J.



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&apping :

(t is process of thread cutting inside a drilled or a bored hole using a tool called taL) special attachment containing a reversing mechanism is re*uired for tapping.

pecification of drilling machine

(" The si e of the working table and capacit$ of the machine.0" Maximum si e of the work piece on the particular machine.=" Maximum diameter of drill on the particular machine.>" Humber of spindles on the particular machine.5) #ength of arm and column diameter must be specified for radial drilling machine.


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