Metrics forMechanics

Self-Study ProgramCourse Number 921003

Audi of America, Inc.3800 Hamlin RoadAuburn Hills, MI 48326Printed in U.S.A.June 2001

Metrics, Tools and Measuring

Volkswagen of America, Inc.

Service TrainingPrinted in U.S.A.Printed in 4/2001Course Number 821003

© 2001 Volkswagen of America, Inc.

All rights reserved. All information contained inthis manual is based on the latest productinformation available at the time of printingand is subject to the copyright and otherintellectual property rights of Volkswagen ofAmerica, Inc. All rights are reserved to makechanges at any time without notice. No part ofthis publication may be reproduced, stored ina retrieval system, or transmitted in any formor by any means, electronic, mechanical orphotocopying, recording or otherwise, normay these materials be modified or re-postedto other sites, without the prior permission ofthe publisher.

All requests for permission to copy andredistribute information should be referred toVolkswagen of America, Inc.

Always check Technical Bulletins and theVolkswagen Worldwide Repair InformationSystem for any information that maysupersede any information included in thisbooklet.

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Metric System Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Measurement Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Vernier Caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Micrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Dial Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Dial Bore Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

Feeler Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Torque Wrench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Course Goals

Goals

After completing this self-study course,you should:

� Be comfortable with measurementsand calculations using metric units

� Understand the functions, advan-tages and limits of various measur-ing tools

� Know why to choose a particulartool for a particular job

Introduction

As a technician, you use many differentkinds of tools to make effective repairs,and to help make your job faster andeasier. Some are common hand tools,used with skills that you developed early,through your own experience. Others arespecial tools and test equipment with veryspecific functions that may require specialtraining. For this course, we want to focuson measuring tools.

Like other special tools, these requiresome specialized knowledge and training.Precise measurement techniques are notfoolproof. There are correct ways to usethese tools to achieve meaningful results.Whether diagnosing a problem, evaluatingwear, verifying proper specifications ormaking precise adjustments, accuratemeasurements can be the foundation ofan entire repair. Remember, too, that anymeasurement is only as accurate as thetool you are using to make it. We need tounderstand the limits of our tools, and notexpect more precision than they candeliver. Careful handling of the toolsthemselves is also necessary to ensurethat they maintain their accuracy.

The title of this self-study course, Metricsfor Mechanics, has a double meaning.�Metric� is a word that dictionaries defineas a noun, meaning �a standard ofmeasurement� or �a means of specifyingvalues.� So, when we say �metrics� werefer to the science of measurement.�Metric� is also defined as an adjectivereferring to the �metric� system ofmeasurement�based on the unit of lengthcalled a �meter.�

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In this course, we are concerned with bothmeanings. We will explore the use ofmeasuring tools and the task of makingmeasurements, including capabilities and limitsof various tools, how to choose the best one fora particular task, and how to make accuratemeasurements.

We will also be almost exclusively talking aboutmeasurements based on units of the metricsystem. Volkswagen designers and engineerswork in metric units. The factories check theirwork and evaluate quality using metric units. Itfollows, then, that the specifications we find inthe repair literature and use in our repairs arealso given in metric units. To start, we willhighlight the basics, so this will also serve as ametric system refresher course.

The self-study program is divided into anintroductory section, as well as separatesections on:

� Vernier calipers

� Micrometers

� Dial indicators

� Dial bore gauges, feeler gauges and torquewrenches

You have the option of covering each sectionindividually, as time permits, before completingthe Teletest.

Metric System Basics

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Metric System Basics

As a Volkswagen technician, you need tobe able to understand and work withmetric units and measurements. Our carsare designed and built according to metricspecifications, and it�s what we see in theofficial service and repair informationsupplied by the factories.

You are already familiar with units ofmeasurement that are similar to the metricsystem, and some that are much morecomplicated. In the common Englishsystem, we know that there are 12 inchesto a foot, three feet to a yard, 1,760 yardsto a mile, and so on. There are also eightounces to a cup, two cups to a pint, twopints to a quart, and four quarts to agallon! The only reason we �know� andcan recall these relationships, is that weuse them often and probably have themmemorized. Otherwise, there is little logicor common sense to fall back on.

Relationships in the metric system are allbased on factors of 10, 100 and 1000. Thebasic unit of length is the meter, and otherunits of length are all derived frommultiplying or dividing by 10. Without anymemorization, the inherent logic of thesystem always applies when convertingbetween larger and smaller units.

You already know and use a similarsystem�the system of currency usingdollars and cents. Our basic unit ofcurrency is the dollar, and a basic smallerunit�the cent�is 1/100th of a dollar. Wealso tend to think of larger amounts ashundreds and thousands of the basicdollar unit. (We�ll ignore, for now, the factthat we also use quarters and $20 bills!)

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Metric System Basics

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In the metric system, the basic unit�themeter�may be expressed as smaller unitssuch as centimeters (1/100th) ormillimeters (1/1000th). Larger units arealso described in multiples of 10. A milemay be 5,280 feet, but a kilometer isexactly 1000 meters!

If we need to convert from one unit toanother in the metric system, we only needto know how many times to multiply ordivide by 10. 1000 millimeters equals onemeter. 10 millimeters equals onecentimeter and 100 centimeters equals onemeter. It�s all determined by factors of ten,a hundred or a thousand.

We can get a practical feeling for theserelationships from a simple metric ruler.The smallest divisions are millimeters,about the same as the thickness of a dime.Ten of these smallest divisions are equal toone larger division�a centimeter. And, forexample, 40 smaller millimeters are exactlythe length of four larger centimeters. If ourruler were a meter stick, one meter long,we could also see for ourselves that 1000millimeters or 100 centimeters equal onemeter.

ConversionsStarting with: To convert to: Multiply by: -or- Divide by:

Millimeters (mm) Centimeters (cm) 0.1 10Meters (m) 0.001 1000

Centimeters (cm) Millimeters (mm) 10 0.1Meters (m) 0.01 100

Meters (m) Millimeters (mm) 1000 0.001Centimeters (cm) 100 0.01

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Measurement Basics

Measurement Basics

There are a few basic concepts about theaccuracy of measurements and measuringtools that are worth examining.Understanding these basics will help youdetermine exactly how much confidenceyou can have in a particular measurement.

It will also help you choose tools that areprecise enough to give accurate results forthe measurement you are making. Evenan inexperienced technician would not tryto measure a shim thickness or pistondiameter with a ruler. The tool is simplynot precise enough for the task, and anymeasurement would be hopelesslyinaccurate.

You might use a caliper or micrometer tomeasure shim thickness, because it isdescribed by precise specifications, butyou would not use such tools to checkbrake pad thickness, because that level ofprecision just isn�t necessary, and it wouldbe a waste of time.

Any time you choose a measuring tool,you must ask yourself some questions:

1. What is the smallest unit or part of aunit that needs to be measured?

2. Does the measuring tool allow one toreliably read units that small?

3. If so, is the tool accurate at that degreeof precision?

To answer these questions, we considerthe precision of the specification for thevalue to be measured. The specificationitself contains all the informationnecessary to determine how accurate themeasurement, and the tool, needs to be.The key is the number of significant digits.

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Measurement Basics

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Precision and significant digits

A specification expressed as �4 mm� hasno significant digits to the right of thedecimal point. With no specific tolerance,the implied degree of precision calls formeasurement to the nearest millimeter.We want about 4 mm�closer to 4 mmthan 3 mm, and closer to 4 mm than 5mm. This measurement requires somejudgment, but requires a tool no moreprecise than a ruler marked in millimeters.

A specification of �4.0 mm� is different. Atfirst, it appears to be the same as 4 mm,but there is an extra digit to the right of thedecimal point�the value is more precise.The implied degree of precision calls formeasurement to the nearest 0.1 mm or1/10th millimeter. While 3.9 mm or 4.1 mmare very close, they are different from 4.0mm, and do not meet that specification.

A ruler is almost good enough to measure4.0 mm, because 4 mm and 4.0 mm arefundamentally the same. But, considertrying to measure 4.3 mm with a ruler.Could you read 4.3 mm accurately? With aruler marked in whole millimeters only, wehave to visually estimate how far 4.3 isfrom 4.0, and from 5.0. Such estimates areunreliable because there is no precise wayto read 1/10th millimeter the same wayevery time. It requires a more precise tool,such as a vernier caliper.

A specification of �4.00 mm� is even moreprecise. There are two significant digits tothe right of the decimal point. This means4.00�not 3.99, and not 4.01�so it isimplied that we want to be able tomeasure accurately to the nearest 0.01mm or 1/100th millimeter. A very goodcaliper may be sufficient but, generally,this degree of precision demands amicrometer or dial indicator.

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Measurement Basics

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Expressed tolerances

Until now, we have describedmeasurement precision and accuracybased on implied tolerances�the degreeof precision that is suggested by the way aspecification is expressed, and thenumber of significant digits. In somecases, the factory will specify the samekind of nominal or desired value, and alsoclearly express a tolerance or range ofvalues that is acceptable.

Example:

Valve head diameter � 39.5 ± 0.15 mm

According to the base specification of 39.5mm, and the number of significant digits,we might assume the degree of precisionto be to the nearest 0.1 mm. In fact, thefactory intends to express a slightlybroader, less precise tolerance. Thisspecification means that the nominaldiameter is 39.5 mm (39.50), but anythingwithin the range from 39.35 to 39.65 mmis acceptable.

Example:

Valve length � 91.9 +0/�0.90 mm

Notice that, in this case, there are differenttolerances permitted for values greaterthan or less than the specified nominalvalue. �+0� indicates that there is notolerance for values greater than thenominal value�and the maximumallowable length is the same 91.9 mm(91.90) as the nominal value. On the otherhand, it is allowed to be shorter. Any valuewithin the range from 91.90 mm down to91.00 mm is acceptable.

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Measurement Basics

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Practical complications

A specification does not always clearlyindicate the degree of precision intendedby the factory. The real meaning can bemore complicated. Consider an example:

Brake pad thickness:Application #1: 11 mmApplication #2: 12.5 mmApplication #3: 14 mm

The specifications for #1 and #3 suggestthat we need to measure pad thickness tothe nearest millimeter. Does #2 need to bemeasured with 10 times the precision, tothe nearest 1/10th millimeter (0.1 mm)?Probably not. By comparing the similarspecifications, we can assume �12.5�really means �12 + 1Ú2� mm, a value thatcan only be expressed as 12.5 mm.

Let�s look at another example:

Piston dia.: Bore:Application #1: 80.985 mm 81.01 mmApplication #2: 79.48 mm 79.51 mmApplication #3: 82.485 mm 82.51 mm

Do these applications require differentdegrees of precision? It seems unlikely.Measuring cylinder bore diameter to thenearest 1/100th millimeter (0.01), andpistons to the nearest 1/1000th mm (0.001)makes little sense. Comparing similarspecifications, we can determine that werequire measurements to the nearest1/100th mm. Piston diameter #1, forexample, should be �halfway� between80.98 mm and 80.99 mm, which can onlybe expressed as 80.985 mm.

Specificartions like these require you tomake a judgement. Use your knowledgeand experience to determine whether thelast significant digit indicates greaterprecision, or the extra �5� is just �1Ú2.�

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Vernier

Caliper

Vernier Caliper

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Vernier Caliper

Perhaps the most common and versatileof the precision measuring tools in theworkshop is the vernier caliper. Twodifferent sets of jaws are designed tomake outside measurements such ascomponent thickness, and insidemeasurements such as hole diameter orclearance between parts. Most verniercalipers also have a mechanism for depthmeasurements, such as a difference inheight between two parallel surfaces.

The jaws are specially designed so that,when used carefully, they are properlyaligned and perpendicular to themeasured surfaces. This helps producemeasurements that are as accurate aspossible.

The name refers to its unique measuringscale, the vernier scale, named for 17th

century mathematician Pierre Vernier. Itprovides a reliable and repeatable meansof estimating fractions of millimeters, andgives a higher level of precision andaccuracy.

This vernier caliper is specially designed fordepth measurements. It is used here tomeasure the position of a valve stemrelative to the top of the cylinder head, toensure proper clearance for hydraulic valvelifter operation.

This large vernier caliper is being used toprecisely measure the overall height of acylinder head.

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Vernier Caliper

The vernier caliper�s main scale is verymuch like a conventional ruler. It measureswhole millimeter. In this way, the verniercaliper is no more precise than any otherruler.

The difference lies with the second scale,the vernier scale. Do you remember theproblem we had trying to estimate 10ths ofmillimeters on a ruler? The vernier scale isdesigned to overcome that problem andgive us a reliable and repeatable way tomeasure fractions of millimeters with anadditional degree of precision.

Depending on the type of vernier scale, avernier caliper may be accurate to thenearest 1/10th (0.1) or 5/100ths (0.05)millimeter. This degree of precision isuseful for many routine measurements thatneed to be made in the workshop.

Some vernier calipers are equipped withvernier scales that can reliably indicatemeasurements to the nearest 2/100ths

(0.02) mm. Any measurements that requiregreater precision than a vernier caliper callfor the use of a micrometer.

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Vernier Caliper

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A dial caliper operates the same way as avernier caliper, except that it combines theversatility of a caliper with the mechanicaldisplay of a dial indicator. Likewise, adigital caliper offers the benefits of anelectronic digital display. A dial or digitalcaliper is more expensive than a verniercaliper, but easier to read. For informationabout reading a dial caliper, see thesection on dial indicators later in thisbooklet.

Reading a vernier caliper

A combination of steps is used to arrive atthe final, most precise reading. Withpractice, the sequence will becomesecond nature. For now, however, we willexaggerate the details of each, and treatthem as separate steps to make the wholeprocess more clear.

Step 1 � Whole millimeters

First, use the main scale to determine thevalue to the left of the decimal point�theinitial part of the measurement in wholemillimeters (mm). When the jaws are fullyclosed, when the caliper reads zero, the�0� on the vernier scale is exactly alignedwith the �0� on the main scale.

As we open the caliper jaws to make ameasurement, the �0� mark on the vernierscale acts as a pointer. Use it to read thefirst part of the measurement�the numberof whole millimeters. Count the number oflines that appear between the �0� on themain scale and the �0� on the vernierscale.

Digital caliper�all the function and versatilityof a vernier caliper, with the added simplicityand convenience of digital read-out.

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Vernier Caliper

Example:

In this example, we count four lines from�0� on the upper scale (arrow), anddetermine that the measurement is at least4 mm, but not as large as 5 mm.

Try the next two as exercises. What is thefirst part of the measurement, the wholemillimeter (mm) value, indicated in eachcase?

In the first exercise, we should count 11lines from �0� on the main scale, so thewhole millimeter value is 11 mm and theindicated measurement is at least 11 mm,but less than 12 mm.

In the next exercise, we count lines andfind that the �0� pointer from the vernierscale is between the 17th and 18th lines onthe main scale. If you said 3 mm, youmade the mistake of taking your readingfrom the end of the sliding vernier element,where it overlaps the main scale. Usingthe �0� mark for the first part of themeasurement, the whole millimeter (mm)value, we read 17 mm.

Always use the �0� mark on thevernier scale as the pointer tocount whole millimeters.

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Vernier Caliper

Step 2 � Fractions of millimeters

For the next part of the reading, thesimilarity to a ruler ends. Vernier�s scaleallows us to accurately read tenths ofmillimeters, which we could never do witha ruler.

You will notice that the vernier scale isshort. Its total length represents just onewhole millimeter. In the version shown,there are ten increments marked along itslength, labeled �0� to �10,� so eachincrement represents 1/10th millimeter.

We emphasize the word �represents�because, as we can see, these marks aregreater than 1/10th mm apart. In fact,these �1/10th mm� increments are largerthan the whole millimeter markings on themain scale. By the genius of Vernier�sdesign, we are able to use these large,easy-to-see markings to accurately readvalues that are actually much smaller.

Once we have determined the �crude� partof the measurement in whole millimeters,we shift to the vernier scale and use it tocount 1/10th millimeters. Here�s how:

In the first illustration, the caliper readszero. The �0� pointer is exactly alignedwith the �0� on the main scale. Notice, too,that the �0� mark and the �10� mark on thevernier scale are the only marks that lineup with a mark on the main scale.Remember that for later reference!

In the second illustration, we have openedthe caliper exactly 1 mm. The �0� on thevernier scale no longer reads zerobecause, of course, it now reads 1 mm.Notice, too, that the �10� on the vernierscale is still lined up with a mark on themain scale, but it is a different mark.

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Vernier Caliper

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To make sense of this, let�s look at a thirdillustration. The caliper is open exactly 1Ú2mm (0.5). The �0� pointer line on thevernier scale lies, as we expected, halfwaybetween 0 and 1 mm (left arrow).

To count 10ths of millimeters, find the oneline on the vernier scale that lines up,exactly, with any line on the main scale. Inthis example, it is the line at the �5�marking (right arrows), representing5/10ths millimeter, or 0.5 mm.

Let�s try two other examples. These twoappear to be, at first glance, almostidentical. They are, however, indicatingaccurate readings of two very differentmeasurements.

The first example indicates 0.3 mm. Theline on the vernier scale that lines up withone on the main scale is the third one(arrows), indicating to 3/10ths or 0.3 mm.

In the next example, we find that twodifferent lines are in alignment (arrows). Ifwe count the lines on the vernier scale, wecan see that this example is indicating7/10ths or 0.7 mm.

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Vernier Caliper

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Step 3 � The complete reading

OK, now let�s put it all together to make acomplete reading. We will go over thecomplete process, from beginning to end,using a new example.

First, we determine the �crude� part of thereading: what is the measurement to thenearest whole millimeter. Remember toalways use the �0� mark on the vernierscale as a pointer to read the main scale.Count the lines between �0� on the mainscale and �0� on the vernier scale.

Each line on the main scale is onemillimeter. In this example, we count tenmillimeters or one centimeter, indicated bythe �1� on the main scale, plus two morefor a total of 12. Our measurement liesbetween 12 mm and 13 mm (arrow).

Next, we determine what fractional part ofa millimeter remains, using the vernierscale. Looking closely, we see that justone line on the vernier scale lines up withjust one line on the main scale (arrows).Counting on the vernier scale now, wecount that as the eighth line. Each lineindicates 1/10th millimeter, so our vernierscale is indicating 8/10ths or 0.8 mm.

Finally, we add those two values togetherto get the total measurement. 12 wholemillimeters, plus 8/10th millimeter, makes atotal of 12.8 mm.

12 mm + 0.8 mm = 12.8 mm

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Vernier Caliper

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Example:

Using the �0� mark on the vernier scale asa pointer, we count seven millimeters onthe main scale (left arrow). Then, we lookfor the one line on the vernier scale thatmatches up with a line on the main scale(right arrows). On the vernier scale, wecount that as the seventh line. Each of the10 lines on the vernier scale indicates1/10th millimeter, so our vernier scale isindicating 7/10ths or 0.7 mm.

7 mm + 0.7 mm = 7.7 mm

Example:

We count two whole millimeters on themain scale (left arrow). Then, we see thatthe fifth line on the vernier scale, labeled�5,� is the one that lines up with a line onthe main scale, so our vernier scale isindicating 5/10ths or 0.5 mm.

2 mm + 0.5 mm = 2.5 mm

Example:

The �0� pointer falls just past the 1 cmmark on the main scale, so we are reading1 cm or 10 whole millimeters (left arrow).Turning to the vernier scale, we see thatthe ninth mark lines up with the mainfractional scale, for a reading of 0.9 mm.

10 mm + 0.9 mm = 10.9 mm

Many vernier calipers aremarked in both English andmetric units. As you have seen,multiple steps are required toread a vernier caliper. Avoidgetting confused about whatscale you are using.

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Vernier Caliper

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Reading other vernier scales

Different types of vernier calipers arecapable of different degrees of precision.We have just seen an explanation of onecommon type, which is accurate to thenearest 1/10th millimeter. Others arecapable of greater precision because oftheir design, and the scales they use.

To review, the short vernier scale alwaysrepresents one whole millimeter. In ourearlier examples, that one-millimeter scalewas divided up into ten equal parts, soeach part represents 1/10th millimeter.Another caliper might feature a one-millimeter scale divided into 20 or 50equal parts.

In this case, the "0" to "10" vernier scalestill represents one millimeter, but it isdivided into 20 equal parts instead of ten.The ten lines representing 0.1 mm areeach subdivided by a smaller line. Each ofthese represents 1/20th millimeter (0.05).

Knowing this, of course, becomesimportant when we are counting lines onthe vernier scale. We have to know whatpart of a millimeter each line represents.With this more precise vernier scale, wehave a way to read values like 5.25 mm,which fall midway between 5.2 mm and5.3 mm, as shown (arrow).

Let�s look at one more type of vernier scale.The complete "0" to "10" vernier scale stillrepresents just one millimeter, but it isdivided into 50 equal parts. Each line nowrepresents 1/50th millimeter (0.02), so wecan read to the nearest 0.02 mm, readingvalues like 4.22 mm in the example shown(arrow).

We take measurements with any precisionvernier caliper the same way, as long as wetranslate the lines on the vernier scalecorrectly.

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Vernier Caliper

Example:

The main scale remains the same. Eachline marked on the main scale indicatesone millimeter. In this example, we countsix whole millimeters (left arrow).

Again, just one line on the vernier scale isaligned with another on the main scale.Counting on the vernier scale now, wecount that as the ninth line. The differenceis, there are now 20 lines on the vernierscale representing 1 mm. Each lineindicates 1/20th millimeter, or 0.05 mm, soour nine lines on the vernier scale indicate9 x 0.05, or 0.45 mm.

6 mm + 0.45 mm = 6.45 mm

Example:

The main scale is the same. Each linemarked on the main scale indicates onemillimeter. In this example, we countseven whole millimeters (left arrow).

Again, just one line on the vernier scalelines up with a line on the main scale.Counting on the vernier scale now, weread 0.5 mm plus three more lines. Sinceeach line indicates 1/50th millimeter, or0.02 mm, those three lines on the vernierscale indicate 3 x 0.02, or 0.06 mm.

7 mm + 0.5 + 0.06 mm = 7.56 mm

Any measurement using avernier caliper must be madewith the jaws or the depth gaugeexactly perpendicular�at rightangles�to the measuringsurfaces. Otherwise, they will beinaccurate.

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Vernier Caliper

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Review/Quiz

Use the examples on this page to testyour understanding of how to read avernier caliper. For clarity, the marks onthe two scales that line up are indicated bythe vertical reference lines.

Correct answers are included at the backof the booklet (see page 52).

Example 1

The vernier caliper reads __________ mm

Example 2

The vernier caliper reads __________ mm

Example 3

The vernier caliper reads __________ mm

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Micrometer

Micrometer

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Micrometer

Types of micrometers

A micrometer, like a vernier caliper, isused to make precise measurements oflength. Most are capable of measuring tothe nearest 1/100th of a millimeter (0.01mm or 0.0004 in.).

There are three common types: outside,inside, and depth micrometers.

An outside micrometer measures outsidedimensions. It may be used for precisemeasurement of thickness, or to measurethe outside diameter (OD) of a cylindricalshape like a crankshaft journal or a piston.

A typical outside micrometer

An outside micrometer being used to meas-ure crankshaft journal diameter.

Micrometer

An inside micrometer measures length ordistance between two parallel surfaces.That may be a space between twocomponents, or the inside diameter (ID) ofa nominally round component, such as aconnecting rod bore. It is a bit moredifficult to use than an outside micrometer.The tool must be exactly perpendicular tothe measured surfaces. Any deviation fromperpendicular, caused by holding the toolat an angle, will produce a reading that istoo large.

Even with the inside micrometer at thecorrect perpendicular angle, it can bedifficult to get an accurate measurement.You are trying to measure at the largestdimension at any particular point. Anydeviation from this true diameter willproduce a reading that is too small.

A depth micrometer measures dimensionssuch as the position of a valve seat in acylinder head. The term �depth� refers toany type of distance measured from a flatreference surface. In the case of a valveseat position, the reference surface is theflat surface of the cylinder head.

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Volkswagen special tool VW385/30 is a typeof depth micromter used in the set-up offinal drive assemblies.

Typical inside micrometer, most often usedto measure inside dimensions such as borediameter. Note: the micrometer shownreads in non-metric units.

Micrometer

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Micrometers have a relatively small range.Choose the right one for a particular job,making sure that the nominal dimensionyou want to measure falls within the rangeof the tool. Micrometers are available invarious sizes, to measure from less than amillimeter to over 100 mm (approx. 4 in.).

Anatomy of an outside micrometer

The horseshoe-shaped frame holds theanvil and spindle, a spindle lock, thesleeve and the thimble. Measurements aredetermined by the distance between themoving spindle and the fixed anvil. Thethimble rotates to move the spindle backand forth over very precise distances.

Measurements are made using scalesmarked on the sleeve and thimble. Themain scale on the sleeve is actually anupper scale marked in 1 mm increments,and a lower scale that effectively indicates1Ú2-millimeter increments. The position ofthe thimble along these two parts of themain scale indicates measurements to thenearest 0.5 mm.

The index line on the main scale is usedto read the even more precise 1/100th mm(0.01 mm) increments of the scale markedaround the diameter of the thimble. Thethimble scale is evenly divided into 50increments corresponding to 0.01 mmeach. One complete revolution of thethimble equals 0.5 mm, one 1Ú2-mmincrement on the sleeve, and a 1Ú2-mmmovement of the spindle.

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Micrometer

Operating a micrometer

When the thimble is turned so that thespindle is just making light contact with theanvil, the micrometer should read zero.The end of the thimble should be preciselyaligned with the �0� mark on the sleeve,and the index line should be preciselyaligned with the �0� mark on the thimble.

To measure an object, hold it against theanvil with one hand, while rotating thethimble to move the spindle toward theobject with your thumb and forefinger.Continue turning until the spindle makeslight contact with corresponding side of theobject.

Do not tighten the spindle tooforcefully against the measuredobject. It may damage themicrometer frame and/or destroyits calibration.

Tighten the micrometer just enough that itdrags slightly as you try to shift or removethe object. Some micrometers have asmall knob on the end of the thimble,connected to a clutch mechanism.Tightening the micrometer using this knobrather than the thimble will ensure that youare applying just the right amount of force.If you apply too much force, the clutch willslip to prevent damage.

Reading a micrometer

A combination of steps is used to arrive atthe final, most precise reading. Withpractice, the sequence will becomesecond nature. For now, however, we willexaggerate the details of each, and treatthem as separate steps to make sure theprocess is clear.

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Micrometer

Step 1 � Whole and half millimeters

First, use the main scale to determine thepart of the measurement expressed inwhole millimeters. The micrometer readszero when the edge of the thimble isexactly aligned with the �0� on the mainscale.

Opening the micrometer to take ameasurement, the edge of the thimblemoves along the main scale. To read thefirst part of a measurement�the numberof whole millimeters�count the lines thatappear between the edge of the thimbleand the �0� on the main scale.

Remember that the top of the scale on thesleeve is marked in 1 mm increments. Themarks on the bottom scale subdivide themarks on the top, and these bottom marksindicate 1Ú2-millimeter increments. Countwhole millimeters using the top of themain scale.

Example:

In this example, the thimble is indicating ameasurement between 7 mm and 8 mm.We know this, because we can countseven lines on the upper part of the mainscale. From this, we determine that themeasurement is at least 7 mm.

Compared to a vernier caliper, we are nowadding an extra step. The bottom part ofthe main scale on the sleeve allows us tomake this initial reading to the nearest halfmillimeter. Once the initial number ofwhole millimeters is known (seven in theexample above), look to see if another lineis visible on the bottom part of the scale. Ifso, this indicates that another 1Ú2-millimetershould be added.

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Micrometer

27

Example:

In this example, we count seven lines onthe upper part of the main scale, but wecan also see an additional line on thebottom part of the main scale. From this,we determine that the measurement is atleast 7-1Ú2 or 7.5 mm.

7 mm + 0.5 mm = 7.5 mm

Try this initial reading, using the next twoexamples as exercises.

What is the first part of the measurement,the whole millimeter (mm) value, in eachcase?

Using the bottom part of the scale, shouldwe add 1Ú2 mm to the whole millimetervalue?

In the first exercise, we can count ninelines on the main scale. There is anadditional line visible just past that, on thebottom part of the scale. From thispreliminary reading, we can tell that themeasurement will be at least 9.5 mm, butless than 10 mm.

In this next exercise, we count lines andfind that the edge of the thimble fallsbetween the fourth and fifth lines on themain scale. In this case, however, noadditional line is visible below the indexline. From this preliminary reading, we cantell that the measurement will be at least 4mm, but less than 4.5 mm.

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Micrometer

28

Step 2 � Smaller fractions ofmillimeters

After that initial reading, which is �a littlemore than� the nearest 1Ú2-millimeter, weneed to find out how much more. We willread the more precise fractions of amillimeter from the scale on the rotatingspindle. The thimble and spindle turn onvery fine, precisely machined threads, andaccurately indicate 100ths of a millimeter.

The entire circumference of the thimble isinscribed with a scale, divided into fiftyequal parts, and marked from �0� to �50.�Each of the fifty increments of rotationequals 1/100th millimeter of spindlemovement. A full rotation equals 50/100ths

or 1Ú2 mm (0.5)�the distance between amillimeter mark on the main scale (top)and the next 1Ú2 mm mark on the bottommain scale.

The reading from the thimble tells us howmuch, in 100ths of a millimeter, to add tothe initial measurement. Here�s how.

In the first illustration, the micrometerreads zero. The edge of the thimble isaligned with the �0� on the main scale, andthe �0� on the thimble scale is aligned withthe index line on the sleeve.

In the second illustration, we have openedthe micrometer exactly 1.5 mm. The edgeof the thimble no longer aligns with �0�because, of course, it now reads 1.5 mm.Note that the thimble has made threecomplete rotations (3 x 50/100ths =150/100ths or 1.5). The �0� on the thimblescale is still exactly aligned with the indexline on the sleeve.

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Micrometer

29

To make sense of this, let�s look at thethird illustration. The caliper is openexactly 1-3Ú4 mm (1.75). The edge of thethimble lies, as we would expect, halfwaybetween 1.5 mm and 2 mm. To count100ths of a millimeter, find the line on thethimble scale that lines up with the indexline on the main scale. In this example, wesee that it is the line at the �25� mark,representing 25/100ths millimeter, or 0.25mm.

1 mm + 0.5 mm + 0.25 mm = 1.75 mm

Let�s try two other examples. The firstindicates 7.36 mm. The edge of thethimble lies just past the seventh line onthe upper scale. There is no extra linevisible on the lower scale, so our initialreading is between 7 mm and 7.5 mm. Onthe thimble scale, the index line lines upone mark higher than �35� for a reading of�36� or 0.36 mm. Our initial reading of 7mm plus 0.36 mm = 7.36 mm.

7 mm + 0.36 mm = 7.36 mm

In the next example, the edge of thethimble is indicating just 2 mm, but veryclose to 2-1Ú2 mm. It is no surprise, then, tofind the thimble scale reading 0.47 mm�almost 0.50. Our reading is 2 mm plus0.47 mm, for a total of 2.47 mm.

2 mm + 0.47 mm = 2.47 mm

At measurements that are veryclose to the nearest 1Ú2 millimeter,the next line on the main scalemay start to become visible. Becareful not to misinterpret thisand add an extra 0.5 mm bymistake, as in the next example.

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Micrometer

30

A 50 mm standard being used to calibrate a50-75 mm outside micrometer. With 50 mmbetween the anvil and spindle, the micrometershould read exactly 50.00 mm.

In this example, one might assume thatwe should count 2 mm on the main scale,and add 0.49 mm from the thimble scaleto get a total of 2.49 mm. Looking moreclosely, we can see that this would bewrong, since the entire reading is verynear 2 mm. The reading from the thimblescale is �49� instead of �0,� indicating thatthe correct reading is 1.99 mm.

1 mm + 0.5 mm + 0.49 mm = 1.99 mm

Inside and depth micrometers operatemuch the same way, although their scalesmay be graduated in slightly differentways. Determine the most accuratemeasurement you can make on the mainscale, and make sure you understand therelationship between the main scale andthe thimble scale.

Calibration

A good quality micrometer is furnishedwith a calibration standard of a precise,known dimension. It should read exactly0.00 mm when closed, and it should readprecisely the specified dimension whenmeasuring the standard�50.00 mm in theexample shown.

If it does not read correctly, the calibrationof the micrometer should be adjusted. If itcannot be adjusted to read accuratelyunder both conditions, the micrometer isexcessively worn and should be replaced.

Never store an outsidemicrometer in the fully closed or�zero� position. Changes intemperature may cause enoughthermal expansion to increasestress on the components andwarp the frame or damage thesensitive mechanism.

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Micrometer

31

Review/Quiz

Use the examples on this page to testyour understanding of how to read amicrometer.

Correct answers are included at the backof the booklet (see page 52).

Example 1

This micrometer reads __________ mm

Example 2

This micrometer reads __________ mm

Example 3

This micrometer reads __________ mm

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Dial Indicator

Dial Indicator

34

Dial Indicator

A dial indicator is another instrument usedto make very precise measurements ofdistance, accurate to the nearest 1/100th

of a millimeter (0.01 mm or 0.0004 in.).Where a vernier caliper or a micrometermeasures fixed dimensions of parallelsurfaces, a dial indicator is most oftenused to measure a range of movement ormaking minimum/maximum comparisons.Properly set up in one measuring position,it can accurately measure range of freeplay, limits of movement, run-out, etc.

In the workshop, a dial indicator may betypically used to evaluate the condition ofmoving parts�run-out measurements onrotating parts, crankshaft or camshaft endplay, gear backlash and the like. A dialindicator can also be used to indicate theprecise maximum and minimum points ina range of movement, such as camshafttiming based on valve lift, diesel injectorpump timing and stroke, etc.

A typical dial indicator has two scales. Thelarger main scale is marked in incrementsof 1/100th of a millimeter or 0.01 mm. With100 of these increments marked on themain scale, one complete revolution of thelarge needle is equal to 1 mm.

Many dial indicators also have an inner or�reverse� scale that counts travel in theother direction, usually marked in red. It isuseful when, for example, you want to setzero as a midpoint and make directreadings of a range of values on bothsides of that midpoint.

A smaller indicator, inside the large outerdial, counts whole millimeters.

Dial indicator being used to measurecamshaft end play.

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Dial Indicator

The smallest movements are recorded bythe movement of the large needle. Whenthe tracer pin or foot is displaced andmoves toward the indicator, the largeneedle rotates clockwise. It will make onecomplete revolution for each millimeter thepin moves.

Because the dial is very sensitive and willmove very quickly, it can be difficult tonotice if it has gone around the dial morethan once. The small needle turns counterclockwise to count whole millimeters�fullrevolutions of the larger needle.

Mounting a dial indicator

A dial indicator is always used with amounting fixture that allows it to be alignedat the proper angle, and rigidly mounted inthat position. Most mount directly to thework piece with slotted holes and pivotpoints for adjustment. Another popularmount has a magnetic base that can beattached to any flat iron or steel surfacewithout fasteners.

We typically use dial indicators to makevery small measurements. There are twomain requirements for making accuratemeasurements with a dial indicator:

1. Rigid mounting to the work � whenmeasuring, for example, crankshaft endplay in a cylinder block, the dialindicator must be mounted directly tothe block. Only this way can you besure that you are measuring only themovement you intend to measure.Make sure all of the mounting fixture�sfasteners and pivot points are tight.

35

Typical dial indicator mounting, bolted tocylinder head using highly adjustablemounting fixture.

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Dial Indicator

36

2. Mounting in direction of travel � thetracer pin must be exactly aligned withthe dimension being measured.

When measuring shaft end play orthrust bearing clearance, for example,the tracer pin�s movement must beparallel to the shaft.

For measuring run-out, the tracer pin�smovement must be perpendicular tothe shaft or surface being measured.

Reading a dial indicator

The main scale is divided into 100 equalparts. We read values to the nearest1/100th millimeter (0.01 mm) directly onthe main scale. A full revolution is equal toone whole millimeter.

Each millimeter�each full revolution ofthe larger needle�is shown on thesmaller indicator. In this example, it showsthat we have measured two wholemillimeters, plus the 0.66 mm indicated onthe main scale.

2 mm + 0.66 mm = 2.66 mm

This is a simple example. In practice, wecannot use the mechanical limit of the dialindicator as zero. There must always be atleast some travel, some pre-load on thetracer pin, to ensure an accurate reading.

Improper dial indicator mounting(exaggerated in this view). The tracer pin isnot in line with the direction in which play isbeing measured.

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Dial Indicator

37

Any dial indicator will have some play inthe mechanism. Pre-load means slightlyloading the mechanism in one direction totake up that play, so that it does not affectthe accuracy of the measurement.

Mount the dial indicator so it reads greaterthan zero at the minimum point. Onemillimeter of pre-load is a good �rule ofthumb� for most measurements. Initially,near the minimum point, the dial indicatorshould read about 1 mm.

To measure a range of values such asrun-out, read the minimum value, and thensubtract it from the maximum value. Theactual minimum value may be less than 1mm, and this is the reason for the pre-load�to make certain that the tracer pinnever reaches the end of its travel.Measuring a larger range of values mayrequire more pre-load.

To make it easier to subtract, the outerscale can be moved. Once we establishthe precise minimum point, we can rotatethe scale and actually make that pointread exactly zero.

In the top illustration, the minimum valuewith pre-load reads 3.50 mm. In thebottom illustration, we have rotated theouter scale until the needle reads zero.We have moved only the outer scale, sowe can make an accurate reading moreeasily. The needle itself has not moved.

� For accurate measurements,the scale must be set so thatthe indicator reads exactlyzero at the minimum point(lowest reading).

� After adjusting the scale,move the tracer by hand torecheck the zero point.

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Dial Indicator

38

From this point, reading the measurementon the dial indicator becomes a matter ofreading the difference between zero andthe other (maximum) value.

Let�s look at some examples:

Measurement: pump strokeSpecification: approx. 3 mmPre-load: 3.50 mm

In this case, we have chosen a pre-loadthat corresponds to the larger range ofvalues that we expect to measure. With3.5 mm pre-load, a 3 mm measurementshould never exceed the range of travel ofthe tracer pin.

In the first illustration, we have set the pre-load at 3.5 mm. Then, with the tracer pinat the minimum point, the outer scale hasbeen reset to zero. Notice that the readinghas dropped below 3.50 mm.

The second illustration shows the readingat the maximum point. The difference onthe outer scale is 0.57 mm, and the smallscale shows that the total change is lessthan 1 mm. The measurement in thiscase, the difference between minimumand maximum, is 0.57 mm.

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Dial Indicator

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Measurement: end playSpecification: approx. 1.5 mmPre-load: 2 mm

The top of the illustration shows the initialreading at the minimum point, after theouter scale has been reset to zero. Thereading has dropped slightly below the2.00 mm pre-load value.

The bottom part of the illustration showsthe reading with the tracer pin at the pointof maximum travel. The difference on theouter scale is 0.45 mm, but the inner dialalso shows an increase. The large needlehas made more than one rotation (1 mm),but less than two.

The measurement in this case, thedifference between the minimum andmaximum points, is 1.45 mm.

1 mm + 0.45 mm = 1.45 mm

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Dial Indicator

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Measurement: actuator movementSpecification: unknownPre-load: approx. 5 mm

The first illustration shows the readingafter the outer scale has been reset tozero, with the tracer pin at the point ofminimum travel. Notice that the indicatorreading has dropped far below the 5 mmpre-load, but not as far as zero. Thissuggests that 5 mm pre-load is barelyenough.

If the initial (minimum) readingdropped below zero, we wouldwant to start again with morepre-load.

The second illustration shows the readingwith the tracer pin at the maximum point.The difference on the outer scale is only0.03 mm, but the inner dial shows that theneedle has also moved about eight timesaround.

The measurement in this case, thedifference between the minimum andmaximum points, is 8.03 mm.

8 mm + 0.03 mm = 8.03 mm

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Dial Indicator

41

Review/Quiz

Use the examples on this page to testyour understanding of how to read a dialindicator. After answering Example 1, usethat result to derive the answers toExamples 2 and 3 as described below.

Correct answers are included at the backof the booklet (see page 52).

Example 1

Assume that we are measuring from areading of exactly zero.

The dial indicator now reads _______ mm

Example 2

Assume that the first reading (above) is aminimum value, and the reading shown atright is the maximum.

The measurement, difference betweenminimum and maximum, is ________ mm

Example 3

Assume that the first reading (top) was theminimum reading. Then, the outer scalewas adjusted to read zero. The finalreading shown at right is the maximum.

The true measurement is _________ mm

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42

Dial Bore Gauge

Feeler Gauge

Torque Wrench

Dial Bore Gauge

44

Dial Bore Gauge

A dial bore gauge is a special type of dialindicator, with a mechanism designed formeasuring cylinder bores and similarinside diameters. By comparing borediameter measurements at different pointsaround the circumference, we candetermine whether, or to what extent, thecylinder is out-of-round. By comparingmeasurements made at the top andbottom of the bore, we can determinecylinder taper. Both are important ways ofevaluating the condition of the pistons andcylinders, possible causes of symptomssuch as low compression or oilconsumption, and whether or not thecylinder block can be reconditioned.

The dial indicator portion of a dial boregauge functions just like any other dialindicator. The zero point on the scale canbe adjusted as necessary as an aid tomaking a particular measurement.

In the example illustrated here, the zeropoint on the gauge is being pre-set to thenominal dimension specified for the bore.This way, the gauge will directly read thedifference between the actual diameter atany point in the bore, and the nominalvalue.

Dial bore gauge being used to measurecylinder bore diameter. This particular gaugeuses precise shims and extensions to adaptto required measuring range (inset).

This outside micrometer clamped in a vise ispre-set to the nominal bore diameter, and thedial bore gauge is being set to read zero atthat dimension. Any reading greater thanzero translates directly into a measurementof increased cylinder diameter.

Dial Bore Gauge

The critical thing to remember about usinga bore gauge is that it must be positionedprecisely in line with the bore, to measuretrue diameters at any point in the bore.Tipping the gauge even slightly will causethe dial bore gauge to measure a valuelarger than the actual diameter.

The cylinder block must not bemounted to the assembly standwhen measuring bore diameter.The block is deformed by itsown weight under theseconditions, and that stress willresult in false measurements.

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Dial bore gauge measurements must bemade perpendicular to the cylinder bore. Ifmisaligned, as shown, the values measuredwill be larger than the actual diameter and,therefore, inaccurate.

Feeler Gauge

46

Feeler Gauge

A single feeler gauge is a strip of metalmanufactured to a precise thickness. Forconvenience, a typical feeler gauge set ismade up of multiple strips of varyingthickness increments. They are oftenlabeled in both millimeters and inches.

A flat-blade feeler gauge can be used for avariety of measurements including, forexample, piston ring end gap, connectingrod side clearance, or valve adjustment(where applicable). For an accuratemeasurement, the feeler gauge should slipin and out of the gap being measured witha slight amount of drag or resistance.

If there is no resistance, the gap isprobably slightly bigger than the gaugebeing used. If it is too difficult to get thegauge in and out of the gap, the gauge isprobably just slightly too large. Guardagainst forcing a gauge into a gap. Doingso may change the gap you are trying tomeasure, damage the component(s), ordamage the feeler gauge itself.

A wire-type feeler gauge or gap gauge isused to measure spark plug gaps. Someflat-blade feeler gauges are made of brassto allow clearance measurements betweenparts that may be otherwise influenced bymagnetic attraction.

Flat-blade feeler gauge being used tomeasure piston ring clearance.

Feeler Gauge

47

Feeler gauge and straight-edge

Used in conjunction with a straightedge, aflat-blade feeler gauge can be used tocheck a flat machined surface for warpingor other deformation. A straightedge is aprecisely machined bar, designed to bealmost perfectly flat and very resistant tobending, warping or other distortion. Assuch, it is used as standard for judging therelative flatness of other components.Without a doubt, the most commonapplication of this tool is in evaluating thecondition of aluminum cylinder heads.

A straightedge is used in conjunction witha feeler gauge to measure whatever gapmay exist at various points between thestraightedge and the surface beingchecked. Ideally, of course, there are nogaps, and the cylinder head is perfectlyflat. Factory repair information usually liststhe maximum allowable gap with which thecylinder head can be safely re-usedwithout machining or replacing it.

� Several other factors must beconsidered when evaluating acylinder head to determinewhether it can be machined tocorrect problems with flatnessor warping.

� The factory repair informationwill usually list, for example, aminimum cylinder headthickness dimension that isrequired for proper operationof the hydraulic cam followers.Refer to that information andcarry out those additionalmeasurements as necessary.

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Torque Wrench

Torque Wrench

While a torque wrench is not strictly ameasuring tool, we use tightening torqueas an indirect way to measure somethingthat we cannot measure any other way.

A threaded fastener generates a clampingor compression force that will hold twocomponents together. In turn, there is anequal and opposite tension or tensile forcethat actually stretches the bolt. With atorque wrench, we are measuring thebolt�s resistance to being stretched and,indirectly, the force that it exerts to holdthe components together.

A properly installed fastener must be tightenough to stay in tension under vibration,thermal expansion and contraction andother mechanical loads, but not so tightthat the bolt itself "yields" to the tensileforce and stretches permanently, stripsthreads or breaks.

To get bolt tension right, we want to beable to measure bolt length�how muchthe bolt is being stretched. We could, too,except that usually we can�t get to the boltto measure it! So, we settle for the nextbest thing�measuring the twisting forceor torque required to turn the bolt.

Tightening torque

Tightening torque is like any other kind oftorque. It is a twisting force, defined asforce times distance. Force by itself is nottorque. A torque wrench measures thetwisting force acting on a fastener�theamount of force you are applying at thehandle, multiplied by the leverage you getfrom the length of the handle.

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Torque Wrench

Torque wrenches are calibrated accordingto their length, according to the leveragethey will exert on a fastener. Anything thatchanges that length, like the addition of a"crow�s-foot" extension, will effectivelychange the calibration.

With an extension, the applied force isacting through a moment arm of greaterlength. The torque wrench will indicatetorque only according to its length, so itwill read less than the actual torque beingapplied to the fastener.

To calculate the actual torque:

Note that we are talking about tools thatextend the effective length of the wrench.Ordinary socket extensions that give thewrench a longer reach (without increasingits effective length) have no significanteffect on torque readings.

Correct use of a torque wrench

1. To ensure correct torque, make sureyou are applying force at the center ofthe hand grip.

2. Avoid irregular, jerky movements. Applysteady force to reach the desiredtorque. To re-check a value, relax thewrench momentarily, then apply forceagain.

3. Do not try to apply torque values thatexceed the rated capacity of the torquewrench.

4. With an adjustable torque wrench, suchas a �click� type, always store it at itslowest torque setting.

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Torque Wrench

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Types of torque wrenches

Beam-type

The most basic torque wrench is a beamtype. The torque is indicated by simplemechanical deflection. As twisting force(torque) on the fastener is increased, thebeam indicated the deflection on a scaleattached to the wrench handle. Differentsize beams and different overall lengthsproduce torque wrenches with differentoperating ranges.

Typical wrenches measure torque inNewton�meters (N�m) or foot�pounds(ft�lb), while smaller ones are used fortorque values in Newton�centimeters(N�cm) or inch�pounds (in�lb).

A beam-type torque wrench is preferredfor most tasks requiring a torque wrenchbecause it is more reliable. As long as it isproperly maintained�protected againstbending and corrosion�it is simple andaccurate and does not require calibration.

Dial-type

The advantage of a dial-type torquewrench is like the advantage of a dialcaliper over a vernier caliper�it is veryeasy to read. It is, however, more complexand more expensive. The complexmechanism is less reliable and must becalibrated periodically to ensure accuracy.

Types of torque wrenches include, from left,�click� type, dial type, and three versions of thebasic beam-type.

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Torque Wrench

51

�Click�-type

A "click" type torque wrench does not needto be read at all. At a predeterminedtorque value, the handle will move freelyfor a few degrees and make an audible"click." This combination signals that thedesired torque has been reached.

This type of wrench is especially usefulwhen working in tight quarters, when itwould otherwise be difficult to read a dialor otherwise determine when the propertorque value has been reached. Like thedial type, there are some concerns aboutaccuracy and calibration.

This type also has an advantage whendoing non-critical, repetitive jobs liketightening wheel lugs. One might, forinstance use it for the staged tightening ofcylinder head bolts, and then tighten to afinal value using a more precise tool.

Because a "click" type torque wrench usesa kind of pre-load to determine theindicating value, it must always be reset toits lowest setting for storage. This will helppreserve its calibration.

Torque angle gauge

Some tightening torque specifications areexpressed as a conventional torque value(e.g. 100 N�m) plus an additional step,measured as an angle or rotation. Thiscalls for being able to accurately measurethe specified angle. To do so, use a torqueangle gauge.

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52

Review / Quiz Answer Key

Vernier caliper (page 20)

Example 1: 17.85 mm

Example 2: 3.3 mm

Example 3: 5.84 mm

Micrometer (page 31)

Example 1: 9.71 mm

Example 2: 3.78 mm

Example 3: 4.53 mm

Dial indiator (page 41)

Example 1: 2.66 mm

Example 2: 3.97 mm

Example 3: 4.23 mm

Appendix

Unit conversions � Length/Distance To calculate: mm x 0.03937 = in.

mm in. mm in. mm in. mm in.

0.002 0.00008

0.004 0.00016

0.006 0.00024

0.008 0.00031

0.010 0.00039 0.01 0.0004

0.020 0.00079 0.02 0.0008

0.030 0.00118 0.03 0.0012

0.040 0.00157 0.04 0.0016

0.050 0.00197 0.05 0.0020

0.060 0.00236 0.06 0.0024

0.070 0.00276 0.07 0.0028

0.080 0.00315 0.08 0.0031

0.090 0.00354 0.09 0.0035

0.100 0.00394 0.10 0.0039 0.1 0.004

0.200 0.00787 0.20 0.0079 0.2 0.008

0.300 0.01181 0.30 0.0118 0.3 0.012

0.400 0.01575 0.40 0.0157 0.4 0.016

0.500 0.01969 0.50 0.0197 0.5 0.020

0.600 0.02362 0.60 0.0236 0.6 0.024

0.700 0.02756 0.70 0.0276 0.7 0.028

0.800 0.03150 0.80 0.0315 0.8 0.031

0.900 0.03543 0.90 0.0354 0.9 0.035

1.000 0.03937 1.00 0.0394 1.0 0.039 1 0.04

2.000 0.07874 2.00 0.0787 2.0 0.079 2 0.08

3.000 0.11811 3.00 0.1181 3.0 0.118 3 0.12

4.000 0.15748 4.00 0.1575 4.0 0.157 4 0.16

5.000 0.19685 5.00 0.1969 5.0 0.197 5 0.20

6.000 0.23622 6.00 0.2362 6.0 0.236 6 0.24

7.000 0.27559 7.00 0.2756 7.0 0.276 7 0.28

8.000 0.31496 8.00 0.3150 8.0 0.315 8 0.31

9.000 0.35433 9.00 0.3543 9.0 0.354 9 0.35

10.000 0.39370 10.00 0.3937 10.0 0.394 10 0.39

20.000 0.78740 20.00 0.7874 20.0 0.787 20 0.79

30.000 1.18110 30.00 1.1811 30.0 1.181 30 1.18

40.000 1.57480 40.00 1.5748 40.0 1.575 40 1.57

50.000 1.96850 50.00 1.9685 50.0 1.969 50 1.97

60.000 2.36220 60.00 2.3622 60.0 2.362 60 2.36

70.000 2.75591 70.00 2.7559 70.0 2.756 70 2.76

80.000 3.14961 80.00 3.1496 80.0 3.150 80 3.15

90.000 3.54331 90.00 3.5433 90.0 3.543 90 3.54

100.000 3.93701 100.00 3.9370 100.0 3.937 100 3.94

Appendix

54

Unit conversions � Tightening torque

N..m -to- lb..ft (ft..lb) To calculate: N..m x 0.738 = lb..ft

lb..ft lb..ft lb..ftN..m (ft..lb) N..m (ft..lb) N..m (ft..lb)

10 7 55 41 100 7411 8 56 41 105 7712 9 57 42 110 8113 10 58 43 115 8514 10 59 44 120 8915 11 60 44 125 9216 12 61 45 130 9617 13 62 46 135 10018 13 63 46 140 10319 14 64 47 145 10720 15 65 48 150 11121 15 66 49 155 11422 16 67 49 160 11823 17 68 50 165 12224 18 69 51 170 12525 18 70 52 175 12926 19 71 52 180 13327 20 72 53 185 13628 21 73 54 190 14029 21 74 55 195 14430 22 75 55 200 14831 23 76 56 205 15132 24 77 57 210 15533 24 78 58 215 15934 25 79 58 220 16235 26 80 59 225 16636 27 81 60 230 17037 27 82 60 235 17338 28 83 61 240 17739 29 84 62 245 18140 30 85 63 250 18441 30 86 63 260 19242 31 87 64 270 19943 32 88 65 280 20744 32 89 66 290 21445 33 90 66 300 22146 34 91 67 310 22947 35 92 68 320 23648 35 93 69 330 24349 36 94 69 340 25150 37 95 70 350 25851 38 96 71 360 26652 38 97 72 370 27353 39 98 72 380 28054 40 99 73 390 28855 41 100 74 400 295

Appendix

55

N.m -to- lb.in (in.lb), kg.cm To calculate: N.m x 8.85 = lb.inN.m x 10.20 = kg.cm

lb.in lb.inN.m (in.lb) kg.cm N.m (in.lb) kg.cm1 9 10 25 221 2552 18 20 26 230 2653 27 31 27 239 2754 35 41 28 248 2865 44 51 29 257 2966 53 61 30 266 3067 62 71 31 274 3168 71 82 32 283 3269 80 92 33 292 337

10 89 102 34 301 34711 97 112 35 310 35712 106 122 36 319 36713 115 133 37 327 37714 124 143 38 336 38715 133 153 39 345 39816 142 163 40 354 40817 150 173 41 363 41818 159 184 42 372 42819 168 194 43 381 43820 177 204 44 389 44921 186 214 45 398 45922 195 224 46 407 46923 204 235 47 416 47924 212 245 48 425 48925 221 255 49 434 500

50 443 510

N.cm -to- lb.in (in.lb), kg.cm To calculate: N.cm x 0.089 = lb.inN.cm x 0.102 = kg.cm

lb.in lb.inN.cm (in.lb) kg.cm N.cm (in.lb) kg.cm50 4 5 200 18 2060 5 6 250 22 2570 6 7 300 27 3180 7 8 350 31 3690 8 9 400 35 41

100 9 10 450 40 46110 10 11 500 44 51120 11 12 550 49 56130 12 13 600 53 61140 12 14 650 58 66150 13 15 700 62 71160 14 16 750 66 76170 15 17 800 71 82180 16 18 850 75 87190 17 19 900 80 92200 18 20 950 84 97

1000 89 102

Appendix

56

kg.cm -to- lb.in (in.lb), N.cm To calculate: kg.cm x 0.868 = lb.inkg.cm x 9.81 = N.cm

lb.in lb.inkg.cm (in.lb) N.cm kg.cm (in.lb) N.cm

5 4 49 100 87 9816 5 59 110 95 10797 6 69 120 104 11778 7 78 130 113 12759 8 88 140 122 1373

10 9 98 150 130 147120 17 196 160 139 156930 26 294 170 148 166740 35 392 180 156 176550 43 490 190 165 186360 52 588 200 174 196170 61 686 210 182 205980 69 785 220 191 215790 78 883 230 200 2256

100 87 981 240 208 2354250 217 2452

Appendix

57

58

Metrics for Mechanics

The test accompanying this course, #821003, has been prepared and shipped as a separatedocument. Please refer to your copy of that document and follow the testing instructions tocomplete the Teletest.

Additional copies are available by contacting:

Certification Program Headquarters

Toll-free Hotline & Testing�1-877-CU4-CERT (1-877-284-2378)

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Teletest

59

Metrics forMechanics

Self-Study ProgramCourse Number 921003

Audi of America, Inc.3800 Hamlin RoadAuburn Hills, MI 48326Printed in U.S.A.June 2001

Metrics, Tools and Measuring