Laboratory Exercise: Electric Drill
Hello everyone. Welcome back to the lab session. This is the third lab station we are having.
In the last session, you had a product dissection experimentation for a printer and you saw
how to do a formal or a systematic way of dissecting a product, identifying the parts and then
looking at the assembly structure and then preparing a report on the product. So today we will
repeat the same kind of an experiment for a different product.
So today we will look at the experimentation of an electric drilling machine, which is a
handheld drilling machine and as you know a drilling machine has got the electrical elements
and the mechanical parts, so it is actually a combination of both electrical, electronics and
mechanical elements. So we will try to see how to do the systematic dissection of the product
and then identify the product structure as well as look at the parts and its function in the
(Refer Slide Time: 01:20)
So the objectives as in the previous experiment, here also, you will try if you want to
understand the function of the products. So what is the overall function of the products and
then what are the parts and sub-assemblies are there in the product. So any product you will
be able to see many parts and some sub-assemblies which actually provide a particular
function in the product. So you want to identify all those parts and sub-assemblies in the
product and then look at how the parts contribute to the overall functioning of the product.
So whenever you take out a part from the product, you need to look at what actually it is
doing in the product. What is its function in the product? So you do not need to worry about
how you represent the function at this stage. At least you try to understand what actually it is
doing in the product whether it is providing a power conversion or it is trying to transmit the
power or it is providing some support.
So what actually it is doing in the product needs to be identified and then prepare the parts list
and then prepare an assembly chart as the same format for what actually we did in the
previous class and look at the opportunities for design improvement. So now after going
through this you look at the product, as a designer and then see what you can do to make it a
By the better product in terms of additional functions or existing functions or a pursued
problem within the product and how do you actually modify it. That is what you actually
need to look at. So this will be a general objective in almost all of the experiments but only
thing, the final report that you are making may be slightly different in each one of these
experiments that is going to be the difference.
(Refer Slide Time: 03:05)
So this product is an electric drilling machine which is a handheld product, handheld machine
and manufactured by the company Bosch and this is the model GSB 400 professional and the
main function is drilling holes into or through material. So it can be either metal or it can be
wood or any other material can be there where we can use it for drilling holes.
(Refer Slide Time: 03:32)
So just to give you a background, whenever you try to understand a product you need to have
a bit of understanding of the history of the product, how it evolved over a period of time. So
just to give you an idea. The electric drill developed from the idea of a hand drill which
originated when there was a need to create a hole or a way through objects predominantly
made up of stone, metal or wood.
So that was the fundamental requirement. You want to make a hole in a material. It is wood, I
mean, stone or metal so that was the requirement and people used to use sticks as a rubbing
tool to make holes. So very old time, they used to have sticks and then it moved to stone,
metal, etc and that was the earliest known use of a hand drill, using the sticks to make holes
in a wood is the earliest product.
And another similar machine was the bow. So this kind of bow, you can actually use it for
drilling holes. So you have a tool which is placed on the material on which the hole to be
made and then you have a bow kind of arrangement and then move the bow to and fro motion
which will be converted to a rotary motion and then you will be able to make holes.
So these things were actually very common in many places even in India. Maybe 30-40 years
ago because most of the carpenters, there were no electricity in the villages and most of the
carpenters were using a kind of mechanism like this to make holes and later on after the
introduction of electricity only we started getting, instead of having a reciprocating motion
convert to a rotary motion, we started getting electric motors which can actually have direct
rotary motion and then that rotary motion can be connected to the tool and then we can have a
drill to drill the holes.
So these are basically to reduce the human efforts and it uses lever action to reduce human
effort and produce holes deeper and faster. The lever action could be either parallel to the
axis or perpendicular to this also. There were different ways of doing it. So when you prepare
the report you can just have a brief history of the drilling machine and then or the whole
procedure is followed for making holes and then how it actually evolved to the current
drilling machine. So this is the brief history.
(Refer Slide Time: 06:04)
Now, what are the steps to be followed for product dissection? So as I mentioned in the
previous class also, remove the screws, so you will see in this case, there will be 5 screws that
you will be able to see on the product. So remove the screws and give the number and then
put them in a small bowl given to you so that you do not miss it and then remove the housing,
the right housing and then the inner assembly should be visible. So when you remove the
housing you will be able to see the inner assembly.
So remove the mode switch sub-assembly and then that includes the ball washer and plastic
switch. So that is the 1 sub-assembly that you will be able to see and then remove the screws
which are holding the rest of the assembly. So then you will see, once you remove that you
will be able to see a few more screws. So remove those screws and again write down the
procedure which one you are removing first.
Number them and keep them separate one and then the assembly will look like this and then
the chuck assembly can be taken out and you cannot really further dissect the chuck
assembly. So just remove it as a chuck assembly and keep it. There are further parts in it. Of
course, you do not need to go into that level of dissection at this stage because you know
what the purpose of the chuck assembly is and how it is working.
And then the part X can be removed which is marked as here the part X that is basically the
transmission part from where the motor is, motor this is the motor which actually provides
the torque and that is transmitted to the tool over here. So you will see an assembly here. This
actually is the transmission so you will be able to see the gears and other things and then you
will be able to get all the parts done.
So now you have most of the parts taken out. So look at those parts and then try to identify
them, ofcourse your TA will help you to identify the main function of these different parts
and the assembly structure also. So after this you prepare an assembly chart for the product.
(Refer Slide Time: 08:10)
So the report format as in the previous case, we will be doing the same kind of a format in
this lab session also. So you will write down the details of the product as I already mentioned
and then write down the main function of the products and then write a brief history of the
product evolution in terms of the function and form.
(Refer Slide Time: 08:33)
And then write down the procedure, what tools you used and how you did the dissection and
then prepare a list of parts. The parts list which actually contains the part name, material,
sketch, manufacturing methods and approximate dimensions. So whatever you can identify or
whatever the methods you can identify in manufacturing. If you do not, we are not sure, you
can discuss with the TA and then write down the manufacturing methods and then once you
have the parts list, you look at the assembly chart.
So the parts, how different parts contribute to a sub-assembly and how sub-assemblies
contribute to the main product can be identified. So all the parts you can assemble them or
you can actually prepare a chart in terms of how the parts are assembled.
And that actually leads to a product structure where you show the assembly, subassemblies
and the parts and the last part is basically to observe the product and then give your
comments about the products and its functions and then see what suggestion you can make
for improving the product.
So this is the way how you will be preparing the report for this product. I hope you
understood this. Now you can actually go to the TA. TA will show you how to do the product
dissection and then how to identify the parts and its function.
(Refer Slide Time: 10:05)
Okay. So, thank you, go ahead with your experiments.
(Refer Slide Time: 10:09)
Hi, I am Siddhanth. I will today be explaining about the drilling machine. So before you see
the drilling machine, I just want you to guess what are the components that should be inside
(Refer Slide Time: 10:23)
I have some source of power and essentially I will be converting into some rotational motion.
So I have some electrical energy. I am converting into a mechanical form of energy. So that
is what is called a machine and what is a mechanism? So essentially there are 2 kinds of
things. There is something called mechanism and there is something called machine. So in a
machine, we have one input form of energy and we transform that into some kind of output
form of energy.
So what is a mechanism? Do you have any idea about it, just a random guess? So when you
hear the word mechanism, what is the first thing that crops up to your mind? Some steps one
after another. That is what he is telling is some links connected to each other. So whenever I
move the input link, there will be some form of motion to the output link. So that is what is
called as a mechanism.
So you provide some input motion and that will be transformed into output motion and when
I use such a mechanism into some kind of a product, that is called a machine, okay
understood? Am I clear? So the thing is, right now I want you to guess that I am providing
electrical energy and I am getting some form of rotational energy. So what should be the
components that should be present inside our drilling machine?
So I will list it down. What I will do is I list it down and after we open it, we will be opening
this drilling machine and then we will be seeing whether the components that you have told
matches with it or not and what are the usefulness of each and every component.
(Refer Slide Time: 11:51)
So, essentially what it does is, if I provide you this drilling tool will you be able to drill
something? I will provide you with this. So will you be able to drill something? You need the
drill bit. So what it is doing is essentially a motor is providing that rotational motion, but that
rotational motion needs to go into some tool which will provide the cutting action. So that is
essentially called as a drill bit.
I will have some sort of a drill bit. Apart from that I have, right now I have 3 components. So
let us go sequentially. I will have some sort of a power wire.
(Refer Slide Time: 12:30)
The power will go from the power wire. I will have an on-off switch which will be able to
switch it on and off. So do I need to provide some sort of a safety procedure? Suppose there
is a child playing around so in case he presses this. I do not want this to move. So I need to
provide some child lock buttons, so this is yes. So this is what is called a lock button.
There is some sort of a transfer of electrical energy to that of a motor. So I have a motor then
I will have gears. I have a drill bit. So what is missing? The power is transmitted from the
motor. I have the drill bit, but I need something to hold the drill bit. Yeah socket. So
essentially this is what is called as a Chuck. I will tell you what they are, this is a chuck and
this is essentially a chuck key. So what it does is you can see. When I rotate this in one
direction, the diameter of this chuck is increasing.
(Refer Slide Time: 13:38)
This is essentially a 3 fingered chuck. So one of the questions I want to ask is, why is it a 3
finger Chuck? Can I make it 2? It will slip. So essentially what is happening here is the
contact between the drill bit and the chuck is maintained due to the force applied by the
chuck. So I need to have some sort of a force closer that is the summation.
The algebraic sum of the forces should be zero. So this is what is called a universal chuck.
You can note it down. So all of you can note down the components that you have told me, the
first one was the motor. The second one is gear. The third one is the drill bit and the fourth
one is the on-off switch. Till now we have guessed these components only.
And apart from that I have told you that there are some kinds, there are gears, and will talk
about it separately. What are the gears and what are the different kinds of gears and all and I
have been told about some sort of a chuck. So chuck is essentially used to hold something of
radial symmetry. If I have a square will I be able to hold it?
(Refer Slide Time: 14:47)
No. So, I will be able to hold cylindrical objects here. In order to hold objects of different
dimensions, I will have different kinds of chucks. Is the drilling machine seen now or was
there any previous versions of drilling machines available? So drilling machines are what
came 10 to 15 years ago. So before that in villages and all, have you seen any instances of
drilling machines or something similar to that?
I am essentially trying to tell if we have a sharp pointed object and we have thread around it.
Essentially we will roll the object and we will have some sort of a drilling machine. So, I
think the most common example is in villages everybody used to see how we make lassi and
all. So that is one form of a drilling machine. Essentially you have some sort of motion and
you are transferring into another sort of motion.
What happened after that is, they tried to mechanise it by using v-belt pulleys. You know
about pulleys and all. So I have a pulley here. I have made a v-belt around it and I am
transferring power here, which is used to drill that work piece here. That is what you see in
workshops. Huge workshops, they have a universal drilling machine.
After that, have you heard of the company called Decker? Black Decker. Yeah, so Decker is
a company which patented this pistol gun technique. I have some sort of pistol shape. I press
the trigger. I have some sort of a drilling machine. That is what we made a drilling machine
in some sort of a portable machine and what is this company? Bosch. What is Bosch known
for? Mechanical tools.
Bosch came into existence by making automobile parts essentially. The first component that
they made was, not the first component, I guess the most popular component that they made
was the fuel injection. You have seen that in automobile cars and all. So in case you are not
able to understand anything you can ask me.
After that they made several components and this is one of the products. I will just pass this
product and just by looking at the product, I will ask you what you can notice about the
product and all. You can read about the specs, you can read about the name and then I will
ask you what the product is all about and then.
So, essentially when you see this product the first thing you will notice is GSB 400. So what
is 400? GSB must be some kind of product manufacturing line and all. In case I have the first
product line, second product line, so GSB is the code of the product essentially. But 400 is a
number. It should mean something.
Can you make some guess what 400 should be? Dimension. So in case 400 is a dimension, it
will not be 40 centimetre. It will not be 4 meters and it cannot be 4 mm because the 4 mm
drill bit is very small. It cannot be dimensions. Apart from that? Power or it can be a variation
of RPM are you telling? So essentially RPM.
So what it can be 400 RPM or it can be 400 Watts. I will tell you that if you are able to see
when you make a small differential robot and you have 2 motors, they are essentially 100
RPM motors. 400 RPM is not a significant amount of number in order to drill materials. So
400 cannot be the RPM of the motor. Essentially it will be power. It is a 400 Watt.
Essentially what it means is, if you use this product for a time period of 1 hour, the 400 watts
will be consumed, 1 second, 400 watts will be consumed. That is one of the formulas and by
hand how do we get the torque of this? Essentially what I will do is, I will find the force. I
will find the radius at which the force is acting and essentially I will find the torque of this
machine. From the torque of the machine, I will find the power. So power is one of the units
that is given.
(Refer Slide Time: 18:50)
It is given that it is operating at 220V. 220 Hz, so that is, it is operating on AC and the second
thing is given is the RPM. So the drill bit that is provided with this you can see here. It’s
written at 8 ϕ. When you notice ϕ on any of the machining components it is essentially the
diameter. an 8 mm drill bit is provided with this drilling machine and apart from that you can
notice that it is 2800 RPM( min -1 ).
RPM is rotation per minute. So rotation is usually a number. So the unit will be 1 by time, so
that is frequency. So we will have 2800 RPM and so on this side I can see that there are some
dimensions that are noted that is for wood 20 mm, for steel it is 8 mm. So these are
essentially the dimension of the drill bit that are provided.
In order in order to drill steel, you will essentially need that this is the general dimension that
they are noting. So you need to use a drill bit of 8 mm or 20 mm and what is the speed of this.
So you can see that on no load condition it's 2800 that was noted on this and on loaded
condition the impact rate is 44800.
What is this impact rate? When I am drilling something do I have some sort of impact? I have
some sort of impact and essentially does it come on every, if I am drilling this wood will I
have some impact? So the common example that we have seen is that when I use a drilling
machine on a road, they will have huge impacts but when I drill something like wood or steel
it will be smoother.
When I drill something which is brittle and more concrete, I will have some sort of impact
force and this is essentially the RPM that is provided at this impact. So right now we will try
to open this and we will see all of the components.
(Refer Slide Time: 21:03)
So what I want you to do is this is, this is also a plier and this is the cutting plane and we have
this sort of 2 screwdrivers.
(Refer Slide Time: 21:12)
It will have some sort of thread. So essentially the entire screw will have 2 diameters. One is
the diameter of the screw and one is the diameter of the inside component. I will define the
overall that is the nominal diameter is a sub-function of the maximum as well as the diameter
and the second thing that you can notice is the pitch.
When we remove other screws you will notice that some pitch, the pitch of this screw is
different from the pitch of the other screws and I tell you why it is. So the first thing is it is a
cross headed screw, it has a pointed head and the pitch is not essentially a little bit less. So
you need to rotate it more in order to go to a certain depth.
(Refer Slide Time: 22:39)
So the second component is removing the plastic casing. You can write it and paste it.
Removing the screws. The second step was removing the plastic casing. So initially we noted
down a few components. The one is the motor . We can find it here.
(Refer Slide Time: 22:56)
The second one is gears. So where are the gears? So these are the gears. We have found some
sort of a gear and the third is a drill bit. So drill bit is some accessory that will be provided
and all. On-off switch. We have an on-off switch, but what are the components that we are
not able to guess? We noted that there are some vents on the product.
So in case in order to dissipate heat on this product, we need to have some sort of exhaust
fan. So somebody was telling me about this. Essentially you are telling about that. So this is
the cooling fan that we have. In case you want to notice it, you can see that the maximum
number of vents is provided here because the fan is provided here. So this is the cooling fan.
You can write it on a separate side that the components that we are not able to guess and the
second thing is what is this small component?
(Refer Slide Time: 23:53)
Adapter. Not essentially an adapter. Battery no, because we are providing it with some sort of
power. Adapter. So essentially the adapter will convert, it will be a step down or a step up but
this is not some sort of an adapter. So essentially I am doing some sort of conversion here. So
I am providing an AC and there must be some sort of an electrical component that will be
providing the initial torque and all.
So essentially when you see that in automobile engines, when you kick start a bike, there is
something called as a spark plug. So a spark plug is used to initiate the piston action. Just a
spark which will ignite the fire and keep the cycle going. In case of electrical components, the
same function is provided by the capacitor. So you will have some sort of a, so you have a
motor that is essentially the interaction between 2 magnetic fields.
So you will have some sort of a back EMF in the motor. In order to kick start that motion, the
rotary motion will have some sort of a capacitor which will keep it charged at the end. So
providing I have some sort of a power. What will this do? It will have a jerky motion, but you
do not want to provide that jerky motion. So when you switch it off, it will have some sort of
a charge stored over here.
(Refer Slide Time: 25:07)
So when I start it, it will avoid that jerky motion of the drills and the second thing which we
are able to notice. A drill machine can be made with the help of a motor but when you hold it,
it is kind of a bit heavy. So why do we need to make it heavy? Is it a necessary characteristic
or can we make it light?
Heavier the thing is, the more inertia it will have, and with more, the more force you need to
apply in order to move it. So when you need to drill something, you need to make sure that
the drill that you are making is stable. It is perfectly aligned with the work piece. So for that
in order to happen, you need to make it heavy. So the second thing is, we will remove the
(Refer Slide Time: 25:50)
We will remove these 2, these 3 screws. You can note the third step. Remove these small
screws. I have provided an AC so I have 2 wires.
(Refer Slide Time: 26:05)
These 2 are the power cords that are going to the machine. So I have a capacitor here which
will charge and discharge and it will just avoid it from having the jerky motion. So in case it
will have some back EMF, it will be able to control that. So what is back EMF and how is the
interaction happening inside the motor? I will explain to you when we will open the entire
So the third component is we will remove this one. Yeah remove this. So here you can see
that I removed the power cord and I can also remove the capacitor.
(Refer Slide Time: 26:38)
So this is a capacitor. So the capacitor will have some units in Farads. So it will have some
units in Farad and it will be able to store some charge. So it is essentially 15 μ F, you can see
it here. So, have you seen a capacitor anywhere other than this? Have you heard electricians
in your house telling us that we need to change the capacitor?
Fans, right, so in that case also, I need to have some sort of a rotational motion, and capacitor:
what it does is, it will store the charge and it does tweak the motion smoothly. In case you
switch on the fan, you will provide some amount of voltage to it. Essentially some, suppose I
provide 20V, 30 V, 40 V in this case 220 V.
So, in case of 220 V, it will fast rotate, it will have jerky motion. Capacitor will first charge it
up and during this charge period it will provide some amount of energy to it so that this
motion is not at all jerky.
(Refer Slide Time: 27:40)
So now what I will do is, I will remove the chuck assembly from the drilling machine. So this
is essentially called the chuck assembly because it is used to hold the chuck. So I will remove
these 2 screws. The pitch, so you can see that here the pitch is not that uniform but in this
case, it is a machine screw.
So a machine screw is something that you make in a lab machine. Have you seen the lab
machine? So essentially there are, for in order to make these grooves, essentially this is a
cylindrical rod and I make grooves on this, helical screws. So and in this case, I have to
maintain a certain amount of pitch.
So in order to hold metallic components, I will use something called as a machine screw. In
this case, the pitch will be much lesser so that it is able to hold the components more tightly
and the second thing that you can notice is, it has a pointed head and this is not a pointed
head. I can remove this but it is attached to this.
(Refer Slide Time: 28:52)
So I need to remove this too and what is this? When we remove this, we will notice what
components are coming out of it and then I will explain to you what it is. Try removing this
too and this is also cross headed and it is not a machine screw. So right now what I will do is,
you can notice that this component takes power from the power switch and it is connected to
the motor by these 2 things, these 2 wires.
(Refer Slide Time: 29:23)
So I will remove these 2 wires and somebody try lifting this up. So when you pulled it,
something came out of it. I just want 3 people this, 3 people take this and tell me what it is. Is
it a magnet? In case it is a magnet it will stick to the iron piece. So to give the power to this
(Refer Slide Time: 29:47)
To give the power to this motor, I can use a wire. I can use any sort of component other than
graphite, but why graphite. First thing, it is a conductor. Graphite is a conductor. Second
thing is, it has the least amount of friction because of the carbon atoms between it is able to
slide and it has the least amount of friction. So that is the reason we use it not the least but it
has some amount of friction. The second thing that you want to notice here is.
(Refer Slide Time: 30:19)
So these are spring loaded. Yes to hold it and the other thing that you can notice is due to
successive rotation there is wear and tear in this carbon brush. So now I can remove this
entire casing. Let me see if I am able to remove it.
(Refer Slide Time: 30:39)
Yes, so I am able to remove the entire casing. So, first I will remove this enter chuck
(Refer Slide Time: 30:47)
The first thing that you will notice is this is some sort of the gear and I told that gear was used
for transforming motion. So what kind of gear is this? Helical bevel gear. So I will tell you
the different types of gear. The most common form of gear that you will see anywhere spur
gears. So you know what a spur gear is, right? Essentially I will have a circle. I will have a
circle, I will have some sort of teeth and this is helical gear. So in case of a helical gear the
teeth will be in case of a spiral manner.
So what is the main advantage of a helical gear? So I will have some sort of spiral gear. I will
have the corresponding sort of a spiral on the other teeth. So in case of the spur gear, you see
that I have these teeth, I have the other teeth, I need to have a point contact between these 2
sets of teeth. When this contact is lost, I need to rely on the other teeth for transforming the
motion but in case of a helical gear, I will have some sort of helix here.
I will have the corresponding helical here. So I will have entirely a line contact. So essentially
the difference between these 2 are, in order to transmit more amount of force I need to have a
larger contact area for this. In mechanisms, maybe you have read higher pairs and lower pairs
or you will be reading about it. So the higher pair is essentially where you will have a line
contact lying on a plane and the lower pair is where I will have a point. So what are the
different kinds of gears?
One is spur gear, one is helical gear and we were told some sort of bevel gear. So what is the
bevel gear? 90 o rotation. So can you tell me one example where I can use bevel gear. Sewing
machine, okay apart from that, sewing machine is kind of, the first thing you think of bevel
gears that should not be the first example that strikes your mind. The first should be I guess,
any examples that you tell. Sewing machines are obviously one of the applications of bevel
gear, but have you seen a car?
Car? So in the car, I have some sort of an engine. I have some sort of engine. So the power
will be transmitted along the axis of the engine, but you need to transmit the power to the
wheels. So the wheels are essentially 90 o . So you need some sort of a bevel gear in order to
transmit your sources. So the entire assembly in the car, what it is done is, it is kind of a
differential. So I can rotate it with different items also.
When you are making a turn essentially you are having a lower rpm in the inward wheel,
having a greater rpm at the outward wheel. So we will have some sort of a differential there.
So essentially the most intuitive of a bevel gear is
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