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Module 1: Abrasive Machining Processes

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Multi Point Tool Operations

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Video 1: Sawing and Broaching ProcessToday we are going to continue about the practicalmachining processes where in till now we have studied about boring, shaping, planning, threading,turning, and tapping processes. Now we have already entered into the multipointcutting tool processes and we see other processes in the multipoint cutting tool machining processesin this particular class ok. So, what we are going to see in this particularclass is about sawing, broaching, and milling, drilling, as well as reaming then followedby gear cutting and gear hobbing. Just as a part it is gives you only the introductionbecause many of you know about sawing especially milling, drilling, and all those things youknow the mechanics. And if at all you are interested in studyingabout the material removal mechanism, mechanical physics and all those things you can takethe course that I I was repeating and again repeating there is a mechanics of machiningcourse. So, you can take the that is the advanced version of this particular course and someof the senior faculties will teach from the different IIT's ok.From IIT Guwahati also one of the professor is going to teach you the mechanics of machiningwhere you can study about the what is the mechanisms what is the physics about of itand how the mathematical relations and all those things ok.In this particular course I just introduce about the course I just introduce about theprocess only. Now we are moving to sawing process and the sawing this is for the funsake just I kept do not take in a another way. So, this is about the sawing normallyyou might have seen the cutting of trees and all those things in a at the road sides andall places. So, the most important process in cutting of the trees and all those thingsis ah sawing process ok. We see about the sawing process the introductionto sawing process sawing is used to cut the correct workpiece from the raw materials so;that means, that if at all I want to cut the required shapes from a large or the bulk materialnormally you can go for the sawing process. Chips are produced by the succession of smallcutting; that means that there is a series of cutting edges will come and cut the particularcomponent or particular ah bulk material. So, the chips are produced by each and everycutter individually ok. So, multipoint cutting tool as you see fromthis particular process or from this particular process it is having a multipoint cuttingok. So, it will involve by cutting with a multiple points that are there on the cutter. The small teeth's which are nothing, but the cutting edges produces chips progressivelywhen passing through; that means, that it will whenever it passes through the workpieceit will generate particular chip . So, chips are transported by the space between teeththat is called Gullet. I will come back to you in a example whatis gullet and all those things. Gullet is nothing, but a space between two successiveteeth's in a sawing process. So, it is economical because from the point of ah energy wastageand all those thing it will take less energy even people will use for hang saw that ishacksaw so that you can remove that material there is no additional power requirement andall those things used to produce desired shapes and sizes .Various types of hacksaws will be there are ah the sawing processes will be there oneof the thing is the hacksaw that you can see here and the second is band saw . So, bandsaw normally will be there will be a machine where you just ah put the bend ah this bladeand circular saws also will be there. So, it looks like a thin slitting milling cutter,but there are saws to cut the in the wooden industry and small small soft material industryalso. This saw blades are used ok this is about the ah blades configuration. These arethe three 3 of configurations. The equipment if you see there is a horizontalband saw will be there and there will be a vertical band saw. Apart from the hand basedhacksaw apart from the hand based hacksaw if at all you are going for the mechanicalbased or equipment based in that circumstances you will have two types of band saw wherethe previous slide you have seen the blade just you mount the blade on either you verticalor horizontal band saw and you can use it .So, features of the blade if you see normally it will be decided by so many features. Nowif you see the material and tooth forms normally blade thickness should be as minimum as possible,but from the strength point of view and all point of view you have to choose optimally,and the tool spacing that is the ah how the teeth what is the size of the teeth what isthe placement distance between teeth and teeth so that the gullet have sufficient space tooccupy or give the (Refer Time: 05:53) for give space to the chip and tooth sets averageand normally length of the blade. So, if at all some people want to cut thevery very big trees and do not cut the trees ok.
Video 2: Milling ProcessNow, we move on to the broaching process .So, when the broaching process will be normally used in normally whenever you want very verybig holes of different different shapes and all those things where you cannot drill oryou cannot do the other processes normally you can go for broaching operation. It movesa multiple tooth cutting tool linearly to workpiece, work in the direction of tool axisok. This is the broach normally and this is theaxis of the broach and you will generate certain geometry that is conversely which is projectedon the tool you normally just push it and you will get the output. The shape of themachine surface is determined by the contour of the cutting edges ok.So, whatever the shape normally if you see here the gear is there on the gear you wantto make a some slot for that purpose the broaching is used. So, whatever the surface that youare going to get here is nothing, but the contour decides the surface that you are goingso I want a keyway path here on the gear. So, the broaching operation which is havingthe contour converse to the required shape is used here.So, machining operation is complete in a single stroke; that means, that once if you passon so whether horizontally or vertically it will complete. The teeth are gradually increasingin height so that the final height will be decided by the last teeth of the broach ok.So the broaching material removal mechanism normally the broach is like this. So, whereyou will have a pull type of broach this one and you will pull from this end by puttinginto a existing hole. The prerequisite for the broaching operation is you should havea existing hole then only you can go for the broaching operations.So, now this is the pull end and this is the shank length up to this one where the rootdiameter is there then roughening teeth's. Normally roughening teeth's this red one willhave gradually increasing dimensions of the teeth so the cutting action will be graduallyincreases. As you can see here so the thick the heightof the each cutting edge is gradually increasing. If you see here, if you see here there isa gradually increasing height is there ok; that means, whatever the chip that is takingout by the broach which is nothing, but a tool is used in the broaching operation graduallytakes a thin thin chips from each and every teeth of the broach ok.So, next one is semi finishing teeth this yellow ones are semi finishing teeth's ok.So, this will gives us the semi finish; that means that it would not give me the finalproduct then followed by the finishing teeth, this is green one is nothing, but your finishingteeth. So, finishing teeth will decide the finalshape that I am going to get on this one normally roughening teeth semi finishing teeth andfinishing teeth all will be of the same contour, but the final dimensions will be decided bythe finishing teeth ok. You can see here a one of the examples how the broach; this isthe broach, and this is the final workpiece that is received or it is a final component.So, this contour geometry is generated on the converse geometry generated on the finalproduct. This is about the material removal mechanism in the broaching operation.Broaching normally classified into internal broaching, pull type broaching, and ordinaryand progressive types solid, and sectional segmented type, and profile sharpened, andform relieve type. These are the varieties of the broach and if you can see here normallythe different varieties these are the tools and these are the shapes that is achievedduring. So, one is the spline force; spline is theredouble keyway is there where normally in order to fix the gears system and hexagonal systemis there square, round contours, square is there, rectangle is there. These are the varietiesof the contours that one can generate by using the broaching process.If you see this is the internal broaching normally whenever I want to ah make certainshapes in the internal geometry of the workpiece. Normally you can go for the broach previousslide also deals with internal broaching only. Here again you can see how the broach youcan utilize for the internal geometries of different, different shapes and how the functionof the internal geometries can be explained in this schematic diagram ok. These are theexamples how one can go about to fabricate the broaching operation ok these are the tools,and these are the geometries. So, external broaching also is there.So, suppose somebody want to generate the external. So, normally you can go for someother process also , but you can also look at the broaching operation this is the externalbroaching operation if at all I want to generate this type of contour. So, that this type ofexternal broach is used for this particular application.So, type of broaching machines there are two varieties of broaching machines are there,one is the vertical broaching machine, another one is the horizontal broaching machine. Ifat all you are moving your broach vertically to the workpiece that is perpendicular tothe workpiece that is called vertical. If you are putting along the axis here alsoit will be axis here also so they have their own applications, they have their own fromthe point of energy utilization and all those things some places it is horizontal broachingis good some places vertical broaching is good. So, normally horizontal broaching canbe used for big big workpieces . So, cutting fluid in the broaching since thebroaching operation is very small velocity application where the broach gradually feedinto the workpiece in that circumstances what is the thing is it will go very very slowlyand the material removal will takes very very slowly. So, that dominating feature here isthe friction not the temperature generation; for that purpose you will always go for mineraloil based cutting fluid. You need lubricating character; you need lubrication type of characteristicsrather than the cooling. So, that is why always are the most of the time people go for themineral oil based pure cutting fluids without any water and all those things .Now, we move on to the milling; milling is a well known process and many of you who arelistening to this one has a great knowledge about the milling process because it is theone of the primary process that one can learn in the B. Tech level. So, I am not going totouch much, but however, since is a part of the course just I will introduce about themilling process what are the varieties of milling and all those things.Milling is the most common form of machining to use in any work shop. This is a if yougo to any type of work shop you will find the milling operation vertical milling horizontalmilling universal milling and all these they are varieties milling operations are there.So, at the same time the applications of the milling is too high; that it is a minimumrequirement for a work shop ok. So, lathe and milling these are the two processes whicha small industry also will have in their work shop.Milling is a versatile process capable of producing simple two dimensional flat surfacesto the complex three dimensional surfaces ok. This can developed from the simple twodimension to the complex three dimensions the milling process typically uses the multipointcutting tool cutting tools are called as the milling cutters basically.And these are rotating cutters and capable of high MRR that is the material removal ratewill be very high and the mass production applications is used; that means, that ifat all I want to generate very high amount of a production rate normally one can go formilling process. You can see the milling cutters these are the milling cutters ok. These arethe milling cutters that are used in various varieties of milling operation.The principles of milling milling operation on rotary motion ok rotary motion will begiven to the cutter and workpiece material will be given some feed motion or table feedwill be given and there are different different varieties you can even give in n milling operationor horizontal milling operation you can even give the motion to the cutter also.The milling cutter is spun about its own axis a while the workpiece is advanced throughin such a way that blades of the cutter are able to shave the material; that means, thatit can cut the workpiece material axis is perpendicular to the feeding and the machinesurface is formed one or more passes; that means, that if at all I want very huge amountof material to be removed in that circumstances I have to go for multi passes if at all Iwant to remove very less amount of material you can use in a single but make sure thatyou save the cutter ok. So, otherwise cutters are assume that if youare going for a very thin thin cutters are there. Peoples nowadays talk about micro millingcutters where the RPM goes more than 1000 to 15000 RPM even some of the cutters go around3000 RPM so and the thickness of cutters is very small. So, you should be very carefulwhenever the people who are taking up the milling so there is a micro milling, highspeed micro milling is one of the good areas to take up if at all you are a masters orPhD students and you can work with the different different types of cutting fluids that I havespecified on advanced materials, but make sure that your tool also will be a one ofthe advanced material ok. So, geometry of the cutter normally it isa multipoint cutting tool where if you see the single point cutting tool type of toolbits or embedded on it ok. So, concavity angle will be there, angle rake angle will be there,and radial rake angle will be there. There are different different angles are there theseare all given on the textbooks some of the basic textbooks also will be there.As I said there is a relief angle is there relief angle also called as clearance angleor it is also called as flank angle radiance radial clearance angle and radial relief angleok. These are the different different angles are there in the milling cutter.Conventional milling there are two varieties of milling that is called up milling and downmilling. So, many of you come across this as a basic the conventional is a up millingprocess the most common fed method there. If at all you see the cutter direction andthe workpiece motion are opposite in the direction if you take at that particular tangent atthat particular point. So, if you are workpiece fed against the rotational motion of yourcutter normally at that particular contact point both motions are in opposite directionthat is called up milling. In the down milling if you see it is in thesame direction ok maximum chip thickness at end of the cut you will get ok. So, minimumto maximum is the one thing and this is the good about this particular material. Normallythere is a down milling operation also where you can see that the cutter moves in the samedirection of the workpiece moves the maximum chip thickness at the beginning of cut tothe minimum thickness. So, this is the one of the disadvantage fromthe point of machining because anybody whenever you want to go and play certain game you needa warm up. So, gradually you have to increase the temperature then only you have to playthe game. You cannot directly go and play the weight lifting or basketball or somethingyou need to go for warm up then raise the temperature of the body then get the flexibilityof the body then you play the game. So, from the point of the up milling it isgood because gradually chip thickness will vary from minimum to maximum that is warmup for the cutter ah I am just co relating not exactly just I mean to say is that youstart with the minimum and go to the maximum that will be always better rather than goingfrom the maximum and going to the minimum it is not like first play the weight liftingthen go for just warming up that is not good ok. So, up milling from that particular pointof view is good. So, suited for machining of the thin and hardto hold parts and normally the advantage of this particular process is you may not requirea very good fixturing that is the biggest advantage of the down milling process. Becauseeven even though the fixture is not properly held what will happen since it is cuttingdownwards there is no problem of lifting up the workpiece.One of the biggest advantage at the other advantage if you see the other advantage whatyou can see is easy chip disposal because the chip is coming like this ok. So, the chipis coming like this means because there is no upper side on this one because you areworkpiece feeding is in this direction. So, upper side is here so lower side is this one.So, there is no problem of chip disposal and all those things and reduces the work hardeningand preferred for heat treated alloy and stainless steel this is variety one of the varietiesof the workpice material. This is about the up milling and down millingmany books will give you many differences just go through it, but only biggest advantageof the down milling is you need not go for a very very sophisticated fixturing for holdingthe workpiece. But for the machining point of view one should always try to prefer theup milling because it goes minimum to maximum. There are two varieties of milling processesare there horizontal vertical milling machines means your arbor axis this is the arbor axiswill be parallel to your workpiece in the other case it is perpendicular to your thearbor axis. Arbor is nothing, but where you mount the cutter ok normally cutter is a independentbody compared to the machine there is a difference between machine tool and a cutting tool .So, machine tool is nothing, but complete machine itself is a machine tool and the cutteronly is a cutting tool. So, cutting tool is a sub set of machine tool ok if at all youhave already plays the cutting tool on the machine ok so that is why whenever the definitioncomes vertical and horizontal careful about writing arbor axis rather than the cuttingtool axis also.
Video 3: Drilling, Reaming and Gear Cutting MethodsNow, we move on to the drilling operation.So, drilling operation is the primary operation normally one want to generate any type ofhole ok. If somebody want to do the threading operation you need a hole, if at all somebodywant to do the broaching operation you need a hole, if at all somebody want to do thereaming operation you need a hole ok. Reaming operation I will come after this particularprocess . So, the initial process to develop the hole is nothing, but the drilling operation.So, drilling machine was the primarily designed to originate a hole that means, that startit is a starting step to make any type of internal features ok it is a low cost, andit is a fast process. The hole is generated by the rotating edge of the cutting tool thatis called drill bit . So, the cutting motion is provided by the rotating drill and thefeeding is done by rectilinear motion to the drill are the axial direction.So, normally what is I want to say is the feed motion is given at the same time therewill be a rotating motion also will be there and the workpiece is completely stationary.In in this way the drilling operation will takes, the rotating edge of the drill exertslarge force on the workpiece and the hole is generated it will the edge which is therehere will exert lot of force on the workpiece and exerts the lot of forces and generatesthe hole. So, the material removal normally will bedone by the shearing and extrusion because it is the material removal in the drillingoperation is done by the shearing operation as well as extrusion operation. Because extrusionmeans I am just pushing it into the workpiece at the same time it is shearing means it isrotating by in the stationary workpiece. So, the material removal mechanism will be extrusionfollowed by the shearing operation . Types of drills if you see portable drillingmachines is there, sensitive drilling machines are there, gang drilling is there; that means,that as just now I was telling about some gang. So, where you can have multiple operationscan be done in a single go that is upright drilling with a round column is there at thesame time you have a rectangular box column also will be there these are the varietiesof the drilling machines are available in the market .So, radial drilling machine and multiple spindle drilling machine and deep hole. This is theone of the varieties most of the people may not have seen this is called ah deep holedrilling machine. So, whenever if at all some people want to do the drilling operation normallythrough drilling if at all somebody want to do basically you may choose the very verysmall workpieces. Because if the drill fails or the brokes then it will be a problem neitherthe workpiece is useful for us or at the same time tool also is a big loss that is why thereis specialized tools if at all somebody want to do the deep hole drilling.So, deep hole drilling normally used for those applications where you want to go for thebroaching in the next go. If at all some big workpieces are there from one side drillingwill be done 50 percent. And rotate the workpiece then and just do the other side also ok, thenyou go for the boring operation also you can go because you can enlarge the existing holethen you can go for the broaching operation. So, drill bits normally drill bits have avariety of geometry the geometry is chisel point drill normally tapper shank will bethere this is called ah mores tapper. Normally you might have seen or you might know whatis mores tapper and all those things just you push it into the shank ah fixture whereit has to be held just you ah it will have its own fixing because of the tapper thatis provided that is called mores tapper and this is called the shank length.Let me talk about this particular tool normally this is shank length where this is no rolein the machining process the machining process will be done by the complete body of the drillbit where the flutes are normally provided. If you see this particular image where theflutes are even flute this is the one flute another flute is this one. So, always thedrill bits will have even flutes because to evacuate chips from the both sides so thatthe there would not be any vibrations and all those things ok.So, regarding the three dimensional views you will come in this one. So, you can seethethree views of the drill bit ah where if you take any particular side. If you come it isvery easy to draw so if at all somebody want to practice you can practice with writinga j here and another one j here then you just add ok.Then you take up the other sides and you can take the lengths of other side and you candraw easily ok. So, this say how you can draw and if you see this is the land basicallyland is the cutting edge which is provided so that the complete drill bit will not touchwith the workpiece otherwise the friction of the cutting will goes enormously high thatis why normally land will be provided this point will be there you can see in this onethis is called the point. So, this point always is a initial step tomake a hole that is I told you know that say called extrusion followed by the shearing.So, extrusion part will be done by this point. So, lip angle will play a major role so lipangle as minimum as possible if you have lip angle like this it will have move extrusioninto the workpiece will be better that is about the lip angle.And the normal relief angle also will be provided here chisel edge angle also will be providedthe corners and these are the some of the terminologies that one can use in the drillingprocess. So, the mechanism if at all I want to perform properly then extrusion followedby the shearing you should always choose your proper dimensions of the geometries here.The drill bit terminologies as I explained in the previous slide. This is about the variousterminologies what is the function of the land? What is the function of the heal? Whatis the web or core thickness this core thickness is the one that we will try to extrue theinitial step ok. So the flutes are also provided, if you seethe flutes and the flutes are provided to evacuate the chip, and at the same time drill,if you see the cutting fluid has to go into the machining region for that purpose alsothe flutes will help. These are other terminologies where the point? What is the point? What isthe lip length? What is the lip angle and all those things and what is the point howthe point angle will vary if at all I want to the extrusion or if I want more about theshearing then you have play with this type of terminologies.There are two types of holes one is the blind hole another one is the through hole. Throughhole means I will across the workpiece cross section the hole will be made. Here if itis a blind hole means you do not go to the other side of the workpiece; that means, thatyou will end here itself so; that means, you from other side if you see here it looks blindthat is nothing is there like that you will observe ok so, that is the difference betweena through hole as well as the blind hole. So, drills and drilling operations there arevarieties of drilling operations are there. So, the first one is drilling normal drillingthe second one is core drilling where you can generate these extending type of holeyou can generate. The other one is a step drilling where you can generate this typeof geometry where you will have a extension at the step different steps will be there.So, counter boring the geometry normally you will you are going to get is a step type ofgeometry you will get and the counter sinking. So, in normally the laptop or some other placesto safe guard from the accidents of the scratches and all those things the screws are held inthe counter sinking regions and counter boring regions. So, counter sinking will have a tapperone and you will have a this type of hole .So, reaming; reaming we are going to study normally reamings are used to enlarge theexisting hole and to finish the existing holes center drilling center drilling is a processnormally one can see in the lathe operation to hold the workpiece between the centers.So, on the other side of the machine that is near the tiles stock to put the dead centernormally center drilling will be done. And the gun drilling normally gun drillingwill have a cooling applications normally whenever some people want to make very verylarge holes or I mean to say lengthy holes. So, you need to send the cutting fluid veryfrequently that is about the gun drilling process these are the varieties of drillingoperations are there ok. So, we move on to the drilling materials whereare the materials that are used here is the carbon steels, high speed cutting tools, solidcarbides, coated steels and ah ceramic inserts also be used for that drill bit materialsI am just talking about. Fluids if you see the applications of fluidsyou will have a cooling, lubrication .