measurement instruments

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MEASUREMENT INSTRUMENTS & MARKING OUT (MD-008)

REV 1: Measurement Instruments & Marking out (MD-008) Page 2 of 60

REVISI0N HISTORY Revision Number Date Comments Rev. 0 16-08-2004

Rev. 1 16-09-2004 Signed off by J Kaiser 17-09-2004 ISSUE 1


TOPICS COVERED INCLUDE

Reading Scales accurately Reading Imperial and Metric Micrometers and Verniers Tool handling and care Safety


CONTENTS

MEASUREMENT INSTRUMENTS (MD-008)

1. INTRODUCTION

2. TYPES OF CALIPERS

3. VERNIER CALIPERS

3.1. MAIN FEATURES

3.2. READING A CALIPER: ENGLISH

3.2.1. WHERE DO YOU START?

3.2.2. EXAMPLE 1

3.2.3. SUMMARY

4. READING A CALIPER: METRIC

4.1. EXAMPLE 1

4.2. EXAMPLE 2

4.3. EXAMPLE 3

5. MICROMETERS

5.1. MICROMETER PARTS

5.2. IMPERIAL MICROMETER

5.3. READING THE METRIC: MICROMETER

6. DIAL INDICATORS: MAIN PARTS

7. INTRODUCTION TO LIMIT FITS & TOLERANCES

8. DIMENSION TOLERANCES

9. INTRODUCTION TO FITS

9.1. EXAMPLE OF FITS


9.2. CLEARANCE FIT


9.4. INTERFERENCE FIT


9.6. TRANSITION FIT

10. LIMITS & FITS STANDARDS

11. GO-NO-GO GAUGES

MEASUREMENT INSTRUMENTS: MEASURING & MARKING OUT (MD-008)

12. INTRODUCTION

13. BASIC MEASURING TOOLS 14. READING SCALES ACCURATELY

15. MARKING OUT EQUIPMENT

15.1. PREPARATION FOR MARKING OUT

15.2. METHOD

15.3. MARKING TABLE

15.4. PARALLELS

15.5. VEE BLOCKS

15.6. SCRIBING BLOCK (SURFACE GAUGE)

15.7. UNIVERSAL SURFACE GAUGE

15.8. CENTER POP (DOT PUNCH)

15.9. DIVIDERS

15.10. ODD LEGS (JENNIES) HERMAPHRODITE CALIPERS

15.11. ENGINEERS TRY SQUARE

15.12. COMBINATION SET

15.13. ANGLE PLATE

15.14. RULE STAND

15.15. SCREW JACK

15.16. SCRIBER

15.17. PROTRACTORS

MEASUREMENT INSTRUMENTS (MD-008)


1. INTRODUCTION

Calipers are tools used in the home, small shops, and industrial settings, they

are used to make precise length measurements. Some reasons for their

popularity include:

A wide measuring range (usually between 0 - 6) Both English and metric scales are usually found on the

same instrument

Many different kinds of measurements can be made

While both micrometers and calipers can make outside length measurements, calipers can also make inside measurements and also depth measurements.

Figure 1 Outside Length Measurement

Figure 2 Inside and Depth Measurements


2. TYPES OF CALIPERS

Figure 3 Vernier Calipers

Figure 4 Dial Calipers

Figure 5 Digital Electronic Calipers


3. VERNIER CALIPERS

3.1. MAIN FEATURES

Figure 6

3.2. READING A CALIPER: ENGLISH

To determine the length of an object in inches, you must be able to read the English scale on the caliper

Figure 7 English Scale is on the Upper Edge of this Caliper

Metric vernier scale

Small jaws (for inside measurements)

Metric fixed scale

English vernier scale

Beam

Depth Gauge English fixed scale

Jaws (for outside measurements)


Most of the measurement information is going to come from the fixed English

scale, which can be thought of as a ruler

Figure 8

3.2.1. WHERE DO YOU START?

Use the zero line on the vernier scale

Figure 9

The zero line acts as a pointer, and tells you where to look on the fixed scale.

Reading a caliper is a process of collecting measurements from the fixed

scale and the vernier scale

To stay organized; write down each measurement in a column, being careful

to keep the decimal points lined up.


3.2.2. EXAMPLE 1

The largest fixed scale divisions are the one-inch intervals, so start there first

Measurements

1

Figure 10

Since the zero line is

between 1 and 2, we know the object being

measured is at least 1

long.


The one-inch intervals are broken down into ten smaller ones. Each of these

is worth a tenth of an inch (0.1)

Measurements

1

0.00

Figure 11

Because the zero

line did not go

beyond any of the

one-tenth lines,

you wont add any

of these to the

measurement total.

0.1 0.2 0.4 0.3 0.5 Etc.


The last step is to get a reading from the vernier scale

Measurements

1

0.00

0.050

Figure 12

Each line on the

vernier scale is

worth 0.001

0.005

0.004

0.003

0.002

0.001

Etc...


What you are looking for is a place where one of the lines on the vernier lines

up with a line on the fixed scale

Measurements

1

0.00

0.050

Figure 13

.

It might be difficult to

see on the computer

screen, but notice

how the 0.020 line

from the vernier

coincides (lines up)

with a line on the fixed

scale.


Add the vernier scale number to your list - the last step is to add up all of the

measurements

Measurements

1

0.0

0.050

+ 0.020

1.070

Figure 14


3.2.3. SUMMARY

Example 1

Locate the zero line on the vernier...

Figure 15

Determine the number of whole inches...

Figure 16

1


...The number of tenths (0.1)...

Figure 17

...The number of 0.025 lines...

Figure 18

The zero line did not go beyond

any of the 0.1 lines.

1

0.0

The zero line is beyond the

second 0.025 line but not the

third.

1

0.0

0.05


and finally the vernier reading

Figure 19

The sum of all these measurements is 1.070

Figure 20

The 0.020 line seems to

line up best with a division

on the fixed scale. 1

0.0

0.050

1

0.0

0.050

+ 0.020


Example 2

Lets obtain a reading from this caliper:

Figure 21


Figure 22



Figure 23

The number of tenths (0.1)...

Figure 24

The zero line has not

gone beyond the 1

line, so there are no

whole inches. 0

The zero line on the

vernier scale has gone

beyond the 0.5 line.

0

0.5


The number of 0.025 lines...

Figure 25

and finally the vernier reading.

Figure 26

The zero line on the

vernier scale has gone

beyond the first 0.025

line but not the second. 0

0.5

0.025

The 0.019 line seems

to line up best with a

division on the fixed

scale. 0

0.5

0.025

0.019


The sum of all these measurements is 0.544.

Figure 27

Example 3

Lets obtain a reading from this caliper:

Figure 28

0

0.5

0.025

+ 0.019

0.544



Figure 29


Figure 30

The zero line has gone beyond

the 1 mark but not the 2 mark.

1


the number of tenths (0.1)...

Figure 31

the number of 0.025 lines...

Figure 32

The zero line on the vernier

scale has gone beyond the 0.6

line but not quite to the 0.7 line

1

0.6

The zero line on the vernier

scale has gone beyond

three of the 0.025 lines.

This is equal to 0.075.

1

0.6

0.075


and finally the vernier reading

Figure 33

The sum of all these measurements is 1.689

Figure 34

The 0.014 line

seems to line up best

with a division on the

fixed scale. 1

0.6

0.075

0.014

1

0.6

0.075

+ 0.014

1.689


4. READING A CALIPER: METRIC

As you are about to see, working with the metric portion of a vernier caliper is

a bit easier to deal with. You only need to make two readings; one from the

fixed scale and one from the vernier portion

4.1. EXAMPLE 1

Start by obtaining a measurement from the fixed scale...

Figure 35

This is the fixed scale

used for the metric

readings.


Use the zero line on the vernier to locate your position on the fixed scale

Figure 36

However, since your final reading is supposed to be in millimetres, you need

to view these amounts as millimetres

Figure 37

Each number printed on

the metric scale represents

centimeters.

6 cm 7 cm 8 cm 9 cm 10 cm

Etc.


One trick is to mentally add a 0 (zero) behind each centimetre number.

Figure 38

Since there are ten spaces between each numbered interval, these smallest

spaces must be 1 mm each.

Figure 39

60 mm

70 mm 80 mm

90 mm

100 mm

For example, note

the ten spaces in

this interval.

The smallest

interval on this

scale is 1mm.

For example,

this would be

91 mm...

this is

92 mm 93 mm

etc.


As you can see in this problem, we have a fixed scale measurement of 63

mm.

Figure 40

To finish we must obtain a reading from the metric vernier scale.

Figure 41

The reading is 63 mm since the zero line has gone just

beyond the 63 mm mark, but hasnt reached the 64 mm

mark.

.05

.10

.15 .20

.25

.30

.35

On this scale, each line represents 0.05 mm.


Just as we did on the English vernier scale, we need to look for a place where

a line from the fixed scale lines up with a line on the vernier.

Figure 42

So based upon the two readings (one from the fixed scale, and one from the

ruler) the length must be 63 mm + .50 mm = 63.50 mm

Figure 43

This is read as .50 mm

It appears that these two

lines, line up the best.

63 mm

+ 0.5 mm


4.2. EXAMPLE 2

Lets try another one for practice

Figure 44

First take a reading from the fixed scale and using the zero line from the

vernier to help

Figure 45

The zero line is close, but not quite up to the 20 mm

line. It has gone beyond the 19 mm line however.

Remember that we

need to read the

fixed scale in terms

of millimeters.

19 mm


To finish, read the vernier scale

Figure 46

The final reading then is 19.35 mm

Figure 47

It appears that these

two lines, line up the

best.

This is read as .35 mm

19 mm

.35 mm

19 mm

+ .35 mm

19.35 mm


4.3. EXAMPLE 3

Lets go through one more examples

Figure 48

Use the zero line from the vernier scale to help get a reading on the fixed

scale

Figure 49

The zero line is directly

above the 18 mm line.

Remember that we need to read the

fixed scale in terms of millimeters.

18 mm


Thats it! Since the zero line on the vernier matched up with a line on the

fixed scale, you quit right there

Figure 50

The final reading is 18.00 mm


5. MICROMETERS

Micrometers are precision measuring instruments. They are manufactured in

both the imperial and metric systems. They are usually accurate to 0.01 mm

(0.0005 inch).

5.1. MICROMETER PARTS

Figure 51

Figure 52 Types of Micrometers (Left to Right) Outside, Inside and Depth

RACHET

THIMBLE

BARREL

ANVIL

FRAME

SPINDLE

LOCK


5.2. IMPERIAL MICROMETER

1. Start by verifying zero with the jaws closed. Turn the ratcheting knob

on the end till it clicks. If it isn't zero, do not use.

Figure 53

2. Carefully open and close the jaws around the specimen using the

ratcheting knob till it clicks.

3. First, identify it is between 3 and 4 (0.3).

4. Next, see that it's just past the quarter mark (0.325).

5. Also see that the dial reads between 4 and 5, so add 0.004 to the

0.325 to get 0.329.

Figure 54

0.3

0.325

0.329


6. To get the ten-thousandths place, read the venier scale

7. Look for the line that best aligns with a mark on the dial - in this case 4

8. So add 0.0004 for a final reading of 0.3294

Figure 55

5.3. READING THE METRIC: MICROMETER

The thimble rotates around the cylinder, which has markings every 0.5 mm on

the left hand side of the thimble there are markings right around. The line

labelled 0 is the primary pointer and when this lines up with the central

horizontal line on the cylinder the distance moved is 7mm

Figure 56

0.3294


If we rotate the thimble one complete revolution, the reading will then be

7.50mm (the downward line is not visible in figure 57)

Figure 57

One more complete revolution the reading is now 8mm

Figure 58

We have increased the distance by 0.120mm from 8.000mm, this means that

the reading now is 8.120mm.


Figure 59

If we now rotate the thimble one complete additional rotation, the reading is

now 8.120mm + 0.500mm = 8.620mm

Figure 60


6. DIAL INDICATORS: MAIN PARTS

Dial indicators are manufactured in the imperial and metric system

Figure 61

Dial indicators are precision measuring tools; a plunger moves in and out

from the body and rotates the measuring needle on a dial face. They can

have one or two inch measuring range and can be calibrated in increments of

0.001.

A smaller dial on the face reads each revolution of the larger dial in

increments of 0.100. the outer bezel rotates and turns the numeric scale with

it so that you can set the indicator to zero at any plunger position.

The important thing to remember when using dial indicators is that when the

plunger is depressed the gauge reads positive and when the plunger is

extended the gauge reads negative.

It is also important to remember that when a dial indicator is zeroed prior to

taking readings, the plunger should be in the mid-range position and the

plunger can now move in either direction.

The dial indicators have many uses in the engineering field, and could

include:

Performing Shaft Alignment Checking Shaft Run-Out

Dial face

Plunger

Revolution dial


Check Bearing Endplay Checking surface flatness Machine shop operations

The dial test indicators are manufactured in both the metric and imperial

systems

Figure 62

The dial test indicators are similar to dial indicators but are typically more

precise. They have a smaller range of movement, however instead of a

plunger, they have a small lever arm that moves up and down, which enables

the tip to be inserted in small diameter holes (useful when centring a work

piece in a four jaw chuck for example). The indicator shown has a measuring

range of 0.030, which is much less that a dial indicator. When the tip is at

rest, at its neutral point, it can be moved 0.015 in either direction. The tip of

the dial test indicators can be set at differing angles.

Lever

Dial


Figure 63

Both dial and dial test indicators can be supplied with mounting attachments

such as:

Magnetic bases Clamps Extension rods

Magnetic

base

Dial Extension bar

Clamp


Figure 64

The vertical height gauge has a vertical beam fixed to a flat base. This is

usually used on a marking out table (the datum face). The instrument can be

used for measuring absolute height above the datum surface.

The vernier scale is read in the same way as the vernier calliper. An

allowance may have to be made for the height of the finger. Before use,

lowering the finger onto the datum surface should check the zero reading.

When using a vernier height gauge, make sure that the base of the height

gauge, the surface table and the work piece are kept clean at all times. Bed

the surface gauge and the work piece firmly onto the datum surface.

Secure the fine adjustment clamp and use the fine adjustment screw to bring

the finger lightly into contact with the item being measured, you need to take

the reading in good light to obtain an accurate reading.

Finger

Beam

Fine adjustment

clamp

Base

Fine adjustment

screw

Finger

clamp


7. INTRODUCTION TO LIMIT FITS & TOLERANCES

To ensure the assemblies function properly their component parts must fit

together, however no component can be manufactured to an exact size. A

designer has to decide on an appropriate upper and lower limit for each

dimension.

8. DIMENSION TOLERANCES

If a dimension is specified in millimetres as 10 0.02, the part will be

acceptable if the dimension is manufactured to an actual size of between:-

9.98 mm (the lower limit) and 10.02 m (which is the upper limit)

9. INTRODUCTION TO FITS

The fit represents the tightness or looseness resulting from the application of

tolerances to mating parts, e.g. shafts and holes


Clearance fit (the shaft is always smaller than the hole)

Figure 65

1.495 1.493

1.500 1.502


9.2. CLEARANCE FIT

Enables assembly and disassembly by hand. This creates:

Running and sliding assemblies Free running on high temperature change applications


The definition of interference fit is when the shaft is always larger in diameter than the hole.

Assembly of this is by pressure or heat expansion

Figure 66

9.4. INTERFERENCE FIT

Parts need to be forced or shrunk fitted together this creates permanent

assemblies that retain and locate themselves.

2.003 2.002

2.000 2.001



Transition fit exists when:

Largest shaft is larger than the largest hole But smallest shaft may fit in the largest hole

Figure 67

9.6. TRANSITION FIT

Assembly usually requires press tooling or mechanical assistance of some

kind. This creates close accuracy with little or no interference.

10. LIMITS & FITS STANDARDS

Fits have been standardised. BS 4500 standard ISO limits and fits. ANSI

(American National Standards Institute). BS4500 uses a letter code to

determine the limits, a capital letter denotes a hole and a small letter indicates

a shaft.

1.0071.002

1.0001.005


11. GO-NO-GO GAUGES

Figure 68

These gauges are made for simple pass/fail inspection. There are two

separate or combined gauges for each feature, one gauge must fit inside the

feature and the second must not, so therefore the GO gauge must fit. If the

GO gauge does not fit, the tolerance is above maximum metal tolerance and

if the NO-GO gauge goes, then the feature is below the minimum metal

tolerance.


MEASUREMENT INSTRUMENTS: MEASURING & MARKING OUT

12. INTRODUCTION

There are many types of measuring tools used in industry.

The accuracy of measurements depends on the way these tools are used and

treated.

Measuring tools are delicate instruments. They must be used carefully so as

to retain their accuracy.


13. BASIC MEASURING TOOLS

There are two methods used for taking measurements:

1. The direct reading of a scale by eye

2. By direct contact of the measuring tools on the work-piece

Figure 69 Ruler and Caliper


14. READING SCALES ACCURATELY

Parallax Error

Parallax is the apparent change in position of an object viewed against a

more distant object.

To avoid parallax error:

Hold the scale so that its graduations are close as possible to the part being measured

Sight the graduations squarely off the scale

Figure 70 Measuring Using Graduations Carefully


15. MARKING OUT EQUIPMENT

The term Marking out means scribing lines on a metal surface to indicate

the profile or outline of the finished component.

The profile or outline of any holes that are to be cut in the component and the

position of any hole centres.

Note:

It is essential that when marking out or scribing that an accurate datum or base-reference line be used to ensure correct measurements along the length of the datum. If a base-reference line is not used a compound error may result.

15.1. PREPARATION FOR MARKING OUT

In order that the scribed lines will show up clearly, the metal surface is usually

coated in a contrasting colour.

Whitewash Spectre colour (blue) Copper sulphate solution

15.2. METHOD

The first and most important thing is to establish a datum point and datum lines on the metal. The long edge of the metal should be checked for straightness with the ruler by holding one against the other and holding them

up to the light. Correct any faults with a file. File a second edge at right

angles to the first. Check with the set square.

This right angled corner is your zero point or datum and the two edges are

your datum lines.

All measurements will be taken from these datum.


(Alternatively, you can scribe a line, say 5 mm, parallel to each edge, and use

these as your datum. The point that the two lines cross will be the zero

datum point.)

Take a minute to plan the sequence in which you will work. For example,

start with the main outline, including any radii that the profile might have, then

any cut outs, and then the centers of any drill holes.

15.3. MARKING TABLE

A cast iron table, heavily ribbed for rigidity. It is level and its edges are square

to its face and to each other. It provides a datum surface from which work

may be marked off or inspected. Rough surfaces should not be allowed in

contact with it, nor should articles be dropped, bounced or tapped on its

surface.

Marking tables should be protected when not in use.

Figure 71 Marking Table


15.4. PARALLELS

Machine strips, square and parallel, used for supporting a surface parallel to

the table, made in various sizes, (matched pairs).

Figure 72 - Parallels

15.5. VEE BLOCKS

Machined blocks in pairs with vee grooves for supporting cylindrical work

parallel to table.

Figure 73 Vee Blocks


15.6. SCRIBING BLOCK (SURFACE GAUGE)

Used on marking table to scribe centres and other lines which need to be

parallel to a common base.

Figure 74 - Scribing Block

15.7. UNIVERSAL SURFACE GAUGE

Used to scribe centre lines and other lines to common bases, both the top

surface and edge of marking table. The spindle can be adjusted to various

angles. The scriber point is positioned using a sensitive adjusting screw.

Figure 75 Universal Surface Gauge


15.8. CENTRE POP (DOT PUNCH)

Used for making small indentations or dots along scribe lines and at the

centre of hole positions. Their function is to locate the leg of a pair of dividers

and to witness the position of scribed lines which may be obliterated.

Figure 76 Centre Pop (Dot Punch)

15.9. DIVIDERS

Use to scribe circles and arcs, setting out and checking distances. For large

arcs, distances trammels are used.

Figure 77 - Dividers


15.10. ODD LEGS (JENNIES) HERMAPHRODITE CALIPERS

Used to scribe lines parallel to an edge, find centres of bores, but truth of

lines depends on skill in keeping angles constant while in use.

Figure 78 Hermaphrodite Calipers

15.11. ENGINEERS TRY SQUARE

Used for checking, setting or scribing at right angles. Stock is provided with a

slot to accommodate small burrs. Needs to be accurate to 90 and therefore

must be handled carefully and checked regularly.

Figure 79 Try Square


15.12. COMBINATION SET

The combination set is a versatile measuring and testing tool and consists of

a graduated straight edged or blade which can be clamped to several

different heads.

Figure 80 Combination Sets

The protractor allows the blade to be set at an angle to the flat face.

The square head has one face that forms a right angle with the blade while

the other face forms a 45 angle with the blade.

Figure 81 Square Head


The centre head is designed to allow one edge of the blade to pass through

the centre of two faces at right angles. The centre head and blade are used

for:

a) Finding or making the centre of circular work

b) Checking 45 angle

Figure 82 Using Combination Sets


15.13. ANGLE PLATE

Two surfaces machined at 90 with slots and holes for the supporting of a

work piece at 90 to the table. Box angles are a variation being hollow cubical

boxes machined on all faces with slotted holes.

Figure 83 Angle Plate

15.14. RULE STAND

Fixture for holding an engineers steel rule at 90 to the table.

Figure 84 Rule Stand


15.15. SCREW JACK

Use to raise/level the work pieces at varying heights upon a table, other aids

being steel shims and wedges.

Figure 85 Screw Jack

15.16. SCRIBER

Made from tool steel hardened and tempered at the pit. Used to scribe

straight lines with the aid of a rule, try square or straight edge.

Figure 86 - Scriber


15.17. PROTRACTORS

Protractors have a dial face, graduated in degrees, with straight blade that

can be swivelled to an angle then locked in position. They are used for:

Setting work to an angle Testing angles Marking out the position of holes

Protractors are graduated in degrees only and should not be used for the

accurate measurement of angles:

Figure 87 Protractors

measurement instruments

Documents

gauges measurement instruments

length measurement figure

introduction calipers

vernier calipers figure

measuring marking

english scale

dial calipers figure

types of calipers figure