This document provides an overview of how to use a micrometer to take measurements. It defines the key parts of a micrometer, including the thimble, sleeve, anvil and spindle. The document explains that micrometers can measure distances to the thousandth of an inch. It provides step-by-step instructions for taking a measurement using the sleeve scale, thimble scale and vernier scale. Students are asked to complete an in-class worksheet on using vernier calipers and micrometers and to finish any unfinished portions as homework. They are also assigned a self-test in their textbook on micrometer measurements as additional homework.

1. Prof. Justen Garner
CLT: Mr. Mohammed
New York City College of Technology
Date: 09-23-2019

2. Objectives:
 Learn how to take measurements with a
Micrometer.
 Material covered: Section C Unit 4
 Classwork Handout

3. Micrometer
 A micrometer is a measuring
device used for accurately
measuring minute distances.
 The micrometer consist of a
semicircular frame having a
cylindrical extension, the barrel
(sleeve), at its right end and a
hardened anvil at the other end.
The bore of the barrel (sleeve) is
threaded and a spindle screws
into the bore. The spindle carries
a graduated thimble which turns
at one with it.
 Imperial micrometers typically
measure in 0.001 inches.
 Micrometers have two scales: a
primary scale, on the barrel or
sleeve, and a secondary scale
on the thimble. As shown in the
Fig. B.
Fig. A
Fig. B

4. Micrometer
 Every time the spindle
makes a complete
revolution, the space
between the measuring
faces of the instrument
(the spindle and the anvil)
by 0.025 inch for imperial
micrometers.
 There a number of
different types of
micrometers. The most
common are the outside
micrometers. Inside
micrometers and depth
micrometers.
 They are widely used in
mechanical engineering for
accurately measuring
components.
Fig. C

5. Micrometer Parts
 Measuring FACES - The measured
items are put between the measuring
faces, the anvil and the spindle (also
called - measuring rods). The ANVIL is
the stationary measuring face against
which parts are held until the spindle
makes contact with the work.
 The threaded SPINDLE is the moving
measuring face of the tool. The spindle
extends from the thimble. As the user turns
the thimble, the spindle pushes the item to
be measured against the anvil.
 THIMBLE - The thimble refers to the
revolving portion of a gadget's handle.
Markings on the thimble revolve along
with the handle to align with the barrel's
scale and provide a measuring.
 LOCK NUT - The locking device secures
the spindle and preserves the measuring
so that the micrometer can be removed
from the workpiece before taking the
reading. Some of the gadgets have a
lock nut (as shown), while others may
have a locking lever.
Fig. D

6. Micrometer Parts
 SLEEVE (Barrel) scale - The barrel forms the
uppermost part of the handle; the part closest to
the frame's "U." The barrel is a cylindrical piece
of metal, integral to the frame; the frame and
barrel are molded as one piece. The barrel's
circumference features marks that indicate a
measuring. Because the micrometer-caliper
measures on a micro scale, its calculations are
often lengthy decimals.
 RATCHET speeder-stop - The ratchet speeder
increases the speed at which the spindle rotates,
so the space between the anvil and the spindle
is reduced more quickly than it would be if the
thimble were in use. Using the ratchet speeder
reduces the time it takes to use the gadget.
 The ratchet incorporates a slipping clutch
mechanism that prevents overtightening and
aids the user to apply a constant measuring
force to the spindle, helping to ensure reliable
measurements. If the force were to be excessive
then it would be possible to overstress the frame
thus causing permanent damage to the
micrometer which would in turn lead to incorrect
readings being obtained.
 FRAME - The frame is the basic element of any
micrometer-caliper. The frame appears as a
roughly U-shaped piece of metal. Etched upon
the frame's exterior is a legend, or list, explaining
the graduations indicated on the tool's barrel. A
handle protrudes from one side of the frame so
that its appearance resembles a small scythe.
Fig. D

7. How to measure with a
Micrometer in inches?
 Measurements taken with a micrometer
are a combination of the value shown on
the sleeve scale and the value indicated
on the thimble scale. When using a
micrometer with a vernier scale, the
value on the scale must also be added to
the total.
 Steps:
1. Look at the sleeve scale. The value on
the sleeve scale is the number
immediately to the left of the thimble.
The smallest value that can be read
from the sleeve scale is 0.025”.
2. Look at thimble scale. The thimble
scale of a metric micrometer has a
measuring range of 0.025 inches (one
complete revolution), and is divided into
25 increments. Each increment
represents 0.001 inches.
3. Look at the vernier scale. The vernier
scale of an imperial micrometer has a
measuring range of 0.001 inches and is
graduated in 10 increments. Each
increment represents 0.0001 inches.
4. Add all the readings together.

8. Ex. 1

9. Ex. 2

10. In Class Work:
 Finish the Vernier Caliper and
Micrometer reading.
 Whatever you do not finish in class, you will
finish for Homework.

11. Homework
 Read Sec. C Unit 4 – Complete Self test
on pgs. 133-135