- Here's just one of the specialist tools you'll learn about in the engine building fundamentals course. When it comes to building
engines, the micrometer is one of the most common
pieces of precision measuring equipment that
we're going to be using. Now I know that a lot of
novice engine builders and mechanics really struggle
with how to correctly use and read a micrometer,
so in this module we're going to see exactly
how to go about doing it. Now while there are a few
varieties of micrometer available, we're going to be focusing here on an imperial scaled vernier micrometer. Now of course if you're
using a digital micrometer, using the micrometer is
relatively straightforward because the reading will
be displayed digitally right in front of you. However as we've already found
out, we are going to need a range of different
micrometers, in order to measure the different sizes we're
likely to come across in the engine. And since the digital
micrometer is more expensive than a conventional mic,
this is going to add greatly to the cost of your tool set. Now here in front of me
I have two micrometers, and these are a relatively cheap brand coming out of China, as we
see with a lot of the common equipment we're going
to be using these days in engine building. And in front of me here I
have a zero to one inch mic, and then I have a one to two inch mic. This particular set goes all
the way up to six inches, and we're simply going
to select the micrometer that's suitable for
whatever we're actually trying to measure. Now with the micrometers
there are two different types. There is a vernier micrometer
which is what we're going to be looking at today;
this is able to measure down to four decimal places or 1/10,000 of an inch. Or we can use a conventional
or standard micrometer. This eliminates the
vernier scale and is able to measure down to 1/1,000 of an inch. For today's lesson we will be
looking at the vernier scale, however what we're going
to learn will be applicable to a standard micrometer as well. Before we get started
using the micrometer, we're just going to have
a look at the different components that make up the micrometer. This is our one to two inch micrometer, and first of all we're
going to have a look on the little plaque here; we can see that it's labelled 1-2", and
we can also see that the precision of this
micrometer is also listed; you can see it's listed
at 0.0001 of an inch, or 1/10,000 of an inch. I'm just going to flip it around so we can actually see the scale, and we'll just talk about the different
components of the micrometer. First of all, we have the
frame which actually holds both ends of the micrometer. The two measuring surfaces
are between here and here, this particular component
is known as the anvil, and this part which moves
as we turn the screw thread is known as the spindle. Here we have our measuring
scale, which we'll be looking at in more detail shortly. This particular component
where our scale is written, is known as the barrel or
sleeve of the micrometer. Next we have the turning
component which is known as the thimble. And finally, at the end,
we have our ratchet stop which is what we're going to be using for actually tightening
the micrometer down on the component we're measuring. We also have a positive
stop which we can use to lock the micrometer
once we have measured the component of interest. Now that we've seen the
different components of the micrometer, we're
going to look at how we can actually use a micrometer
to make a measurement. Before we make any
measurements, it's important to make sure that the
measurement faces of the anvil and the spindle are both clean
and free of dirt and debris, as these can have a dramatic
effect on the accuracy of our reading. Now what we're going to do
is close down the micrometer, and just make sure that it is
able to accurately read zero; so what we're looking at
here, is that this zero line here lines up correctly and
accurately with the zero mark on the barrel of the micrometer. Now we're just going
to talk about what each of these increments mean. Now the increments on the
thimble of the micrometer, represent 1/1000 of an inch, so every time we move past
one of these increments, we're increasing by 1/1000 of an inch, so at this point we're reading 5/1000 of an inch. Now every time we go
through one full revolution, we come back to zero. This means that the
micrometer has incremented by 25/1000 of an inch. And we can also see that as we do this, a new mark is now visible on
the barrel of the micrometer. So I'll just open it up a
little bit further so we can see these marks a little bit more clearly. So each of the marks along the barrel represents 25/1000 of an inch, and we can see that
when we get out to four of these marks, we have a value of one, and this represents 1/10 of an inch, or 0.1 of an inch. Now on the top of the scale
here, we have our vernier marks, and these are going to be
used to define our fourth decimal point, or our
1/10,000 of an inch precision, and we'll see how that works shortly. Now that we know a little
bit more about what these numbers mean, let's
actually measure a component and see how this all works. Okay, so now we're going
to actually measure the width of this piece
of aluminium, and you can see how I'm holding the
micrometer; they're made to be used in your right
hand, and while this is a little bit tricky because
it is a small micrometer, you can see I've got my
little finger just looped through the frame, and I'm using my thumb and forefinger on the spindle. We can make coarse adjustments
by using the thimble, but when we get to a
point we're actually ready to make a measurement, it's important to use the ratchet stop,
and this prevents us over tightening the micrometer. So once we've got the
micrometer tightened, and it's stopped moving,
we can then lock it; and we can remove the
component that we're measuring. Let's now have a look
at how we can calculate or measure the component that we've just put in our micrometer. When you're learning to read a micrometer, it's valuable to write down
each of the measurements as you read them, and
then add them together; this makes it very clear
exactly what the measurements are, and we're going to do that. But let's have a look at
what the numbers mean. The first thing we want
to look at it is how many numbers are visible on the barrel or sleeve of our micrometer. Here you can see that
we have the number three being exposed, and what
this means is that we have a measurement of 0.3 inches. Beyond that, though, we
can also see we have three more increments exposed. Remember each of those
increments represents 25/1000 of an inch, so three of those represents 0.075 inches. So we know that at this
point we have 0.375 inches. We can also see though, that,
we've come up just beyond the number five; remember the thimble here represents 1/1000 of an inch, and we can see that we've gone
a little bit past the five. So we're somewhere
beyond 5/1000 of an inch, and this is where the
vernier scale comes in. What we want to do is have
a look at our vernier scale, and see which line comes
closest to lining up. We can see in this point, the six lines up correctly
with our vernier scale, which is our fourth decimal point, or 0.0006 of an inch. Let's write all those down and add them up so we can so we can see
what our final value is. When it comes to writing
down the measurements from our micrometer, it's
always best to look at them each individually, and then add them up. We're going to start
with our 1/10 of an inch measurement, which we
can see here, remember we had our value of three, our measurement of three visible and that
represents 0.3 of an inch. I'm just going to add out
to our four decimal places just so everything lines up when I've got the rest of our measurements listed. Next, we have our little increments, and you'll remember each
of those smaller increments represents 25/1000 of an inch. We can see that three
of these are visible, and that represents 0.075 of an inch, so let's write that down. Now we can see that we've also gone past on our thimble here, we've
gone past our five-thou mark, so we're going to also write that down. And you'll remember that
when we were looking at our vernier scale,
on the top of the mic, we had 6/10,000 of an inch, so we'll write down our
last value there as well. Okay, so this represents the measurement from our micrometer, and
what we need to do now is add up the different values. So, we have 6/1000 of an inch; we have two fives here
which add up to equal 10 so we're just going to carry the one; we have an eight, and a three. So our final measurement
is 0.3806 of an inch. Like any piece of equipment,
using a micrometer does take some practise
to become competent with, but now you should understand the process to go through, and how to correctly read the numbers on the micrometer. That was just one of the modules from the engine building fundamentals course, which is the perfect starting place if you want to learn how to assemble high performance engines. This course will teach you about engine anatomy, essential engine machining processes, how to select and measure critical clearances in your engine, how to assemble the engine long block, and how to break in your fresh engine. For more information and to purchase the course, click the link now.
