Milling Work piece (Basic)

Information Sheet 7.1.1: Precision measuring instruments

 Movable Jaws
Movable jaws are part of the Vernier slide. One Jaw is used for internal measurements and
the other for external measurements.

 Vernier Slides
A Vernier slides moves over the beam and can be set in any position by means of a spring-
loaded thumb lever or simply by pushing it with the thumb.

 Vernier Scale
The Vernier scale is the graduation marked on the Vernier slide. The division on the scale is
called the Vernier divisions.

 Main Scale
Main scale graduations or divisions are marked on the beam.

 Beam
The Vernier slides, and the depth bar attached
to it, slide over the beam. The graduations on
the beam are called the main scale divisions.

 Depth Bar
The dept bar is attached to the vernier slide
and is used for depth measurements.

TAKING INSIDE MEASUREMENTS FIGURE B.2
FIGURE B.3
 The sliding jaw is set slightly
smaller

 The fixed measuring jaw is placed
hard against the component

 The sliding jaw is moved towards
the component

 When taking internal
measurements care must be taken
to ensure the caliper jaws are
parallel to the centre line of bore.

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

TAKING OUTSIDE MEASUREMENTS

 The caliper is first set to a greater FIGURE B.4
dimension.

 The fixed jaw is tightly place
against the component.

 Reading Vernier Caliper
Measurements

 Read the main scale to the left of
the zero of the Vernier in
millimeters.

 Now look at the Vernier scale.

Note: Which one of the Vernier divisions is opposite the line on the main scale.
Then, add the main scale reading to the Vernier reading.

Example 1:

FIGURE B.5

Example 2:

FIGURE B.6

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

C. THE MICROMETER

The micrometer is a precision measuring instrument, used by engineers. Each revolution of
the ratchet moves the spindle face 0.5mm towards the anvil face. The object to be
measured is placed between the anvil face and the spindle face. The ratchet is turned
clockwise until the object is ‘trapped’ between these two surfaces and the ratchet makes a
‘clicking’ noise. This means that the ratchet cannot be tightened anymore and the
measurement can be read.

PARTS OF A MICROMETER CALIPER

FIGURE C.1

Anvil- it is located at the left side of the frame and is found at the opposite of the spindle.

Spindle- it is attached to the thimble revolves with it and moves through the nut in the
frame.

Thimble- rotates with the screw spindle and travels along the barrel.

Sleeve- it is marked 0 - 25-mm range, corresponding to the number of threads on the
spindle. When the caliper is closed, the beveled edge of the thimble coincides with line
marked 0 on the sleeve and the 0 on the thimble agrees with the horizontal line of the
sleeve.

Ratchet- it is used to get the correct measuring force.

Bow/ Frame- it is located at the end of one leg of which carries a fixed anvil, the other leg
carrying a tabular member or barrel.

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

Spindle lock- to prevent any movement of the spindle while you are reading the
micrometer scale.

Measuring Outside Dimensions

 the micrometer is first set to a larger dimension
 is placed with its anvil against the components whilst
 the spindle is rotated and moved towards the components.

On approach of the spindle towards the component,
moved the spindle carefully or use the ratchet.

Excessive measuring pressure results in wrong
readings.

When measuring a fixed component the FIGURE C.2
micrometer is gripped with the left hand and the FIGURE C.3
spindle moved towards the component with the
right.

In the confined places or when the component is
kept in one’s hand, measurements are carried
out with the right hand, as shown.

When measuring a measuring of identical parts it is
advisable to have the micrometer in a special
holder.

Note:

The zero or the starting position of the micrometer FIGURE C.4

has to be checked to ensure accurate

measurements. Under normal measuring pressure the zero lines of the scale barrel as well

as that of the thimble must coincide. When using micrometer with a range above 25 mm the

starting position is checked by means of setting rings or slip gauges. Most micrometers are

constructed so that they can be adjusted when any deviation of their reading occurs during

use.

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

Here’s how to read measurements from a micrometer caliper

1. First read on the barrel scale or sleeve the number of millimeters that are completely
visible.

2. Then add any half millimeters that are completely visible.
3. Note the number of the graduation on the thimble scale that is level with the datum line.
4. And finally, add the thimble reading to the other reading.

FIGURE C.5

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

D. THE VERNIER HEIGHT GAUGE

The Vernier Height Gauge is a development
of a Vernier caliper. In this Vernier instrument
the graduated frame having the main scale is
on the vertical position where the reading is
in the same way as the Vernier Caliper
except that the readings are taken from the
base to the tip or inner surface of the
movable jaw.

FIGURE D.1

To measure with a Vernier Height Gage and Dial indicator

1. Thoroughly clean the surface plate, height gage base, and work surface.
2. Place a finished edge of the work on the surface plate and clamp it against the angle

plate if necessary.
3. Insert a snug fitting plug into the hole to be checked, with about ½ in. (13 mm)

projecting beyond the work.
4. Mount the dial indicator on the movable jaw of the height gage.
5. Adjust the movable jaw until the indicator almost touches the surface plate.
6. Lock the upper slide of the height gage and use the adjusting nut to move the

indicator until the dial registers about one-quarter turn.
7. Set the indicator dial to zero.
8. Record the reading of the Vernier height gage.
9. Adjust the Vernier height gage until the indicator registers zero on the top of the plug.

Record this Vernier height gage reading.
10. From this reading, subtract the initial reading plus half the diameter of the plug. This

will indicate the distance from the surface plate to the center of the hole.
11. Check other hole heights using the same procedure.

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

To Measure Heights Using Gage Blocks

When the hole locations must be accurate to .0005 in. (0.010 mm) or less, a gage block
buildup is made for the proper dimensions from the surface plate to the top of the plug fitted
in the hole.

Follow the procedure build up
1. Prepare the require gage block buildup (the center of the hole height plus one-half
the hole diameter).
2. Mount a suitable dial indicator on a surface or vernier height gage.
3. Set the dial to register zero on the top of the gage blocks.
4. Move the indicator over the top of the plug. The difference between the gage block
build up and the top of the plug will register on the dial indicator.

SOME APPLICATIONS OF A VERNIER HEIGHT GAUGE

1. Laying-out lines on a plate. Notice the work supported behind by an angle plate and
below by a V-block.

2. A dial indicator mounted on the height gauge to check position of tool makers button
in comparison to a pile of gauge block.

3. A precision electronic digit Vernier height gauge being employed to check conformity
of work piece by quality control inspector. Notice tissue paper and acetone for
cleaning.

E. VERNIER BEVEL PROTRACTOR

The vernier bevel protractor measures angles accurately to one-twelfth (five minutes) of
degree.

The protractor dial is graduated into 360, but it is marked 0 - 90, 90 - 0, 0 - 90 and
90 - 0. Each five-degree line is a little longer than the one-degree lines. The longest lines
are the ten-degree lines, numbered 10, 20, and 30, through 90.

The Vernier plate is divided into twelve equal divisions on either side of the zero. Since
there are 60 minutes (‘) in each degree, each line represents 1/12th of one degree (1/12th of
60 equals five minutes).

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

PARTS OF THE VERNIER

FIGURE E.1 FIGURE E.2

Taking Measurements with the Protractor
always ensure that:

1. The legs are contacting the work-
piece in such a manner that no light
gap appears and,

2. That the legs contact the face under
observation vertically.

FIGURE E.4 FIGURE E.3

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

When measurements are taken the universal bevel protractor can be set in a valid for all
settings:

1. When measuring acute angles:
Measured value = read off value

2. When measuring obtuse angles:
Measured value = 180º-read off value

Reading example:

1. Number of whole degrees between the
zero on the dial and the zero on the Vernier
plate.

37  whole degrees FIGURE E.5

2. Number of minutes indicated by the line on the vernier plate that matches a line on the
dial.
40 mi

Final reading= 37 + 40”
Reading = 37º 40’

Example:

FIGURE E.6

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

F. DIAL INDICATORS

Dial indicators, sometimes called clock gauges, are not strictly measuring instruments in the
same sense as a micrometer or a vernier caliper. They are only indicators used to compare
sizes and measurements to a known standard. They are also reliable instruments to align
machine tools, fixtures and work-pieces prior to machining.

PARTS OF A DIAL TEST DIAL TEST INDICATOR

FIGURE F.1

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Information Sheet 7.1.1: Precision measuring instruments

Applications
 To check for run out when fitting a new disc to an automotive disc brake. Run out
can rapidly ruin the disc if it exceeds the specified tolerance (typically 0.05mm or
less).
 In a quality environment to check for consistency and accuracy in the manufacturing
process.
 On the workshop floor to initially set up or calibrate a machine, prior to a production
run.
 By toolmakers (mold makers) in the process of manufacturing precision tooling.
 In metal engineering workshops, where a typical application is the centering of a
lathe's work piece in a four jaw chuck. The DTI is used to indicate the run out (the
misalignment between the work piece's axis of rotational symmetry and the axis of
rotation of the spindle) of the work piece, with the ultimate aim of reducing it to a
suitably small range using small chuck jaw adjustments.
 In areas other than manufacturing where accurate measurements need to be
recorded, eg: physics.

FIGURE F.2

FIGURE F.3

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Worksheet 8.1.1: Check /measure work piece

Learning outcomes:
8 Check/ measure work piece
Learning Activity:
8.1 Check/ measure work piece

Multiple Choice
Directions: Write the letter of the correct answer on the space provided.

_______1. In measurement, the error that is difficult to eliminate is

a. scale error
b. parallax error
c. alignment error
d. arithmetic error

_______2. The reading of a vernier caliper measures to an accuracy of

a. 0.001 mm
b. 0.02 mm
c. 0.01 mm
d. 0.1 mm

_______3. The smallest reading that a vernier caliper can read is

a. 0.001mm
b. 0.01 mm
c. 0.02 mm
d. 0.05 mm

_______4. The advantages that a vernier caliper has over a micrometer is that it

a. it is more accurate
b. is more reliable
c. can measure to 0.01 mm
d. can measure more dimensional features

_______5. The vernier caliper reading shown in figure 1 below is

a. 8.27 mm
b. 8.38 mm
c. 27.38 mm
d. 27.80 mm

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Worksheet 8.1.1: Check /measure work piece

_______6. The vernier caliper reading shown in figure 2 is
a. 10.24 mm
b. 10.34 mm
c. 27.32 mm
d. 27.34 mm

_______7. The vernier caliper reading shown in figure 3 is
a. 31.12 mm
b. 31.70 mm
c. 37.11 mm
d. 37.31 mm

_______8. The vernier caliper reading shown in figure 4 is
a. 2.12 mm
b. 2.18 mm
c. 11.14 mm
d. 11.22 mm

_______9. The vernier caliper reading shown in figure 5 is

a. 51.38 mm
b. 51.64 mm
c. 38.52 mm
d. 38.70 mm

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Worksheet 8.1.1: Check /measure work piece

_______10. The vernier caliper reading shown in figure 6 is

a. 7.92 mm
b. 7.65 mm
c. 79.92 mm
d. 79.65 mm

_______11. The vernier height gauge can be used to measure

a. width of a slot
b. depth of a hole
c. heights and marking out
d. distance between centers

_______12. The smallest dimension that a standard metric micrometer read is

a. 0.01 mm
b. 0.05 mm
c. 0.10 mm
d. 0.50 mm

_______13. One division on thimble of a metric micrometer reads as

a. 0.01 mm
b. 0.05 mm
c. 0.10 mm
d. 0.50 mm

_______14. One turn of the thimble of a metric micrometer moves the spindle by

a. 0.1mm
b. 0.5 mm
c. 1.0 mm
d. 2.0 mm

_______15. To ensure constant measuring pressure when using a micrometer, we must
use the

a. frame.
b. sleeve.
c. ratchet stop.
d. locking lever.

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Worksheet 8.1.1: Check /measure work piece

_______16. The reading on the outside micrometer shown in figure 1 below is
a. 43.68 mm
b. 44.52 mm
c. 46.18 mm
d. 46.68 mm

_______17. The reading on the outside micrometer shown in figure 2 below is
a. 36.83 mm
b. 36.33 mm
c. 43.33 mm
d. 43.83 mm

_______18. The reading on the outside micrometer shown in figure 3 below is
a. 21.24 mm
b. 21.74 mm
c. 21.26 mm
d. 21.76 mm

_______19. The reading on the outside micrometer shown in figure 4 below is
a. 10.18 mm
b. 10.68 mm
c. 19.18 mm
d. 19.68 mm

_______20. The reading on the outside micrometer shown in figure 5 below is
a. 5.43 mm
b. 5.93 mm
c. 14.43 mm
d. 14.93 mm

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Worksheet 8.1.1: Check /measure work piece

Short Answer
Directions: Write on the space provided the correct answer for each statement.

__________________1. A measuring tool use to measure to a moderate degree of
accuracy.
__________________2. French mathematician who invented the vernier caliper.

__________________3. Part of a vernier caliper used for taking external measurements.

__________________4. Part of a venier caliper use to measure depth of a work piece.
__________________5. A measuring tool that measures angles accurately.
__________________6. A measuring tool use to align machine tools, fixtures and work
pieces prior to machining.
__________________7. Part of a micrometer that rotates with the screw spindle and
travels along the barrel.
__________________8. Part of a micrometer attached to the thimble which revolves and
moves through a nut in the frame.

__________________9. A measuring tool use to take readings taken from the base to
the tip or inner surface of the movable jaw.

_________________10. A gauge use to test the accuracy of a micrometer.
.

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010

Worksheet 8.1.1: Check /measure work piece

Checking the work piece (5pts)

Directions: Using the different measuring tools, records all the dimension of the following
work piece.

Work piece Length Width Height Depth

1. Square Block
2. Vee Block
3. T Bolt

Code No. Mill Work piece (Basic) Date: Developed Date: Revised Page #
ALT723307 May 12, 2010 June 12, 2010