How to read an outside micrometer

Please use the information below to help you read our .001" and .0001" outside
micrometers.

Parts of an Outside micrometer

Figure 1: The parts of a micrometer

Sleeve: The Micrometer sleeve is divided into 10 equal parts, each of these parts is
equal to .100" (1 tenth of an inch). Each of these 10 parts is divided into 4 equal parts.
Each of these 4 subdivisions is equal to .025" or one 40th of an inch. More simply, the
line on the sleeve marked "1" represents .100", the line marked "2" represents .200"
and so forth.

Thimble: The thimble is divided into twenty-five equal parts, each of these parts is
equal to .001" and, one complete rotation of the thimble coincides with the smallest
division (.025") on the sleeve.

Figure 2: Example measurements.

Orig. M. Loer 12-17-12

(1) Reading on the Sleeve .200"
(2) No. of lines between "2" and the edge
of the thimble .025"

(3) Thimble line corresponding to the

center line of the sleeve .001"

TOTAL READING .226"

Taking a Reading on a .0001" Micrometer:

To read to one ten-thousandth requires an additional scale called the "Vernier" scale.
The vernier consists of ten divisions, marked on the sleeve, Each graduation of the
vernier scale on the sleeve, represents .0001".

1. Read the sleeve: Follow the same instructions as step 1 above.

2. Read the Thimble: Follow the same instructions as step 2 above.

3. Read the vernier: Each graduation of the vernier scale on the sleeve measures
.0001" (or one ten-thousandth of an inch). To read the vernier, find the graduation
on the vernier scale which lines up with with a graduation on the thimble and read
the number off the vernier scale. In figure 2 above, the vernier graduation
numbered "2" lines up exactly with a thimble line (number "6"), therefore you read
the vernier line "2" which indicates .0002".

4. Add it all up: Now just add all the numbers together to determine the thickness
of your material.

(1) Reading on the Sleeve .200"

(2) No. of lines between "2" and the edge of
the thimble .025"

(3) Thimble has passed .001" line on the

Sleeve .001"

(4) Vernier line that coincides exactly with a

.0002"
Thimble Line
TOTAL READING .2262"

Orig. M. Loer 12-17-12

Blade Micrometer
A blade micrometer is an outside micrometer version, but the ends of the measuring
rods look like a standard screwdriver blade. Blade micrometers are used to measure the
inside of crevices and recesses, such as a pulley. Measurements are taken the same as
with the Outside Micrometer.

Orig. M. Loer 12-17-12

Pitch Micrometer

1–2 inch screw thread micrometer with interchangeable anvils

The pitch diameter of the thread is the most important dimension.

Care must be taken to select the correct anvils for the screw thread to be measured.
Calibration of the pitch mic must be verified with the included standard before each
use.

Orig. M. Loer 12-17-12

Depth Micrometer

The depth micrometer is an accurate and reliable tool to use for depth measurement
(Figure 1). The depths of holes, slots, shoulders, and projections can be measured
accurately to within 0.001 of an inch.

Figure 1 Typical depth micrometer

When using a depth micrometer, two points must be kept in mind. Depth micrometers
measure from a reference plane to a point. The large base of the depth micrometer
(Figure 2) makes up the reference plane. The very small area of the measuring rod
makes up the point of contact.

Figure 2 Measuring distance is from the reference plane to the contact point.

Orig. M. Loer 12-17-12

Figure 3 Depth micrometers read from the right to the left.
With a depth micrometer it is important that the area in which the reference base of the
depth micrometer makes contact with the workpiece is clean and free of dirt or burrs.

The other aspect of the depth micrometer, which must always be kept in consideration,
is that it reads in reverse from other micrometers (Figure 3).

Depth micrometers can be purchased with a number of different length rods, allowing
the measuring tool to be used over a broader range of depths (Figure 4).

Figure 4 Additional rods can be purchased in a variety of lengths.

The head movement of the depth micrometer is one inch. Whenever you use the
micrometer, with the existing rod or to different length rods, check the accuracy of the

Orig. M. Loer 12-17-12

depth micrometer against a known standard (Figure 5).
Figure 5 The depth micrometer is checked for accuracy before every use.

When using the depth micrometer, there is no need to move the micrometer around to
attain the proper feel. In fact, sliding the micrometer should be avoided. The small rods
will wear very quickly and the accuracy of the micrometer may be lost. For greater
accuracy, take several readings at slightly different positions.

Measuring Drilled Holes

When measuring the depth of a drilled hole, it is important to measure at the outside
wall of the hole to obtain the depth of the full diameter portion of the hole (Figure 6).
Hold the measuring rod next to the wall of the drilled hole to assure an accurate full
Diameter depth measurement.

.
Figure 6 Drilled holes are typically measured to full diameter depth

Orig. M. Loer 12-17-12

Vernier Caliper Use

Setting the Origin

Before using your calipers, check that the origin is correct, clean the blades with a cloth
to make sure there's no dust or dirt that would give the wrong measurement and close
the jaws. You should read 0.0mm, if not, check that they're clean and if so, press the
origin button. We've never had to do this since they are pre-origin'd at the factory but
hey, you never know.

Basic Measurements
For the three basic measurements (inside, outside, depth), we'll be measuring a piece
of 20mm extruded aluminum framing.

Orig. M. Loer 12-17-12

Outer Measurement
The first measurement is using the 'outer' jaws. Use the flat part if possible, to avoid
any skewing. Use the thumb-wheel to get a good tight grip on the material. You'll note
it's not exactly 20mm, that's from the manufacturing tolerances, not the calipers.

Inner Measurement
The inner jaws are used to make measurements of slots and holes. These are a little
tougher, make sure you're holding them so you are not getting an 'angled'
measurement that is larger than it should be. I usually take a few measurements and
also 'wiggle' the calipers to make sure they are measuring the minimum distance.

Orig. M. Loer 12-17-12

Depth Measurement
The last basic measurement is depth, often used for drilled holes. This measurement
uses the gauge at the end of the calipers. You'll want to practice how to hold the
calipers to push the tapered end piece down while also keeping the tail flat against the
work, its a little counter intuitive!

Orig. M. Loer 12-17-12

Care and Use of Gage Blocks
Cleanliness is critical.
Gage blocks must be stored clean
and must be recleaned immediately
prior to use.

Gage blocks -- those apparently simple little chunks of steel that are used to
establish an accurate size reference for comparative gages -- are among the most
accurate gages to be found anywhere. Often manufactured to tolerances ±2
microinches for sizes under 1" (or ±0.05 micrometers for sizes 10mm or less), gage
blocks form the basis for almost all other high-accuracy dimensional measurements that
occur in most shops. As such, they're also among the most important of your gages,
and they deserve careful attention to keep them in top condition.

Cleanliness is critical. Gage blocks must be stored clean and must be recleaned
immediately prior to use. Any concentration of dust -- even the amount that occurs
naturally over the course of an hour -- will reduce their accuracy. When wringing two or
more blocks together to build up a stack to the required nominal dimension, any dust,
dirt or grit on the surface of one will tend to score the other and will reduce the
accuracy of the stack. And don't even think about using a block that has been splashed
with cutting fluid -- you know what the suspended metal particles will do to that mirror-
smooth surface.

To clean a gage block, use filtered kerosene, a commercial gage block cleaner or other
high-grade solvent. Wipe it dry with a lint-free tissue, not some shop rag or work apron.
Don't clean blocks by rubbing them against your palm; even if your hands are clean,

Orig. M. Loer 12-17-12

you'll transfer moisture that could promote corrosion. To inhibit corrosion from ambient
humidity while the blocks are in storage, coat them with a noncorrosive oil, grease or
commercial gage block preservative.

Sets of gage blocks are sold in a nice fitted case, which should be considered an
integral part of the gage block system. Keep the interior clean, and keep it closed when
you're not actually removing or replacing blocks. Don't just toss blocks into the case
(and certainly not anywhere else); they'll get scratched and nicked before you know it.
Return each to its proper slot as soon as possible. You'll be able to immediately see
which blocks are in use, and you'll find the ones you want quicker. Keep the exterior of
the case clean, too; it's a clear indication to others that the set should be treated with
care and respect.

Don't loan out individual blocks -- keep the set complete. As soon as a block leaves its
set, you've lost control over how it will be treated, and it may be returned damaged -- if
at all. Inspect blocks frequently for nicks, scratches or burrs. If any such flaws appear,
replace or have the block repaired immediately. A block with a burr or a corroded
surface will quickly damage any other block it is wrung to.

Do not allow stacks of gage blocks to remain wrung together for long periods. The
physics that hold wrung blocks together is not well understood, but experience has
shown that failure to separate blocks may result in them becoming permanently fused
to one another. Even if you use the same set-up day after day, it's good policy to
separate and wring them daily.

Many users compile gage blocks backwards when building up a stack, starting with the
largest possible block and working their way down to the last decimal place. This can be
quite inefficient and often results in stacks that are five or more blocks high. It's
smarter to start small and work your way up. For any nominal dimension under 5",
you'll never need to combine more than four blocks, or more than one from each of the
four series in the set. Furthermore, the fewer the number of wrings, the smaller the
accumulated error in the stack.

As an example, let's use a nominal dimension of 1.3248". We work by creating zeros,

starting from the right. To create a zero in the 10-thousandths place, we have only one
choice in the series of 10ths blocks: the 0.1008" block. Select that block, subtract it
from the nominal dimension, and we've created our first zero. We're down to 1.2240".

We have three choices in the second series of blocks, to turn the thousandths place into
our next zero: 0.104", 0.114" and 0.124". We'll take the last one and kill two zeros with
one stone. Subtract 0.124" from 1.2240", and we're down to 1.1000". Now it's easy.
Pick the 0.1000" block and, last, the 1.0000" block. Four blocks, requiring just three
wrings, and we're done. But don't forget to clean them first.

Orig. M. Loer 12-17-12

Dial Indicators

Points to note

 Dial indicators are used in many types of jobs. They are particularly useful in
determining run-out on rotating shafts and rotors.
 Run-out is the side-to-side variation of movement when a component is turned.
 Dial indicators normally have two separate scales. The needle is able to move
numerous times around the outer scale. One full turn may represent 0.1" or
1mm. The small inner scale indicates how many times the outer needle has
moved around its scale. In this way, the dial indicator is able to read movement
of up to 2" or 1cm.
 Dial indicators can measure with an accuracy of 0.001" or 0.01mm.
 The type of dial indicator you use will be determined by the amount of
movement you expect from the component you are measuring.
 They must be fitted so that there is no movement between the dial indicator and
the component to be measured.
 Most dial indicator sets contain various attachments and support arms so they
can be attached to the component. There are other attachments available. These
attachments allow the dial indicator to be configured specifically for the
measuring task.
 When attaching a dial indicator, keep support arms as short as possible. Make
sure that all attachments are tightened to prevent unnecessary movement
between the indicator and the component.
 Make sure the dial indicator pointer is positioned at 90º to the face of the
component to be measured.
 Always read the dial, face or straight on. A view from the side can give a
considerable "parallax" error. Parallax error is a visual error caused by viewing
measurement markers at an incorrect angle.
 The outer face of the dial indicator can be moved so that the zero can be
positioned over the pointer.

Part 2: Step-by-step instruction

1. Select the correct gauge and attachment

Select the gauge type, size, attachment and bracket, which fit the part you’re
measuring. Mount the dial indicator on a firm surface to keep it still.
2. Ensure plunger is at 90 degrees
Adjust the indicator so that the plunger is at 90 degrees to the part you’re
measuring.
3. Press the plunger halfway in
Press the dial indicator gently against the part, and rotate the part one full turn.
Keep pressing until the plunger settles about halfway into the indicator.

Orig. M. Loer 12-17-12

 4. Lock into position
Lock the indicator assembly into position.
5. Rotate and read
Carefully rotate the part a couple of times, while you observe the dial readings
face on.
6. Record any movements
If the pointer hovers around a single graduation on the dial, the part has minimal
run out, or surface distortion. If it moves significantly left and right, you should
note these variations. Find the point of maximum movement to the left and
move the dial so that zero is over this point. Continue to rotate the part. Find the
point of maximum movement to the right, and note the reading. This will
indicate the run out value. Continue this rotation several times to confirm the
points of maximum variation.
7. Check your results
Check your readings against the specifications. If the deviation is greater than
the specifications allow, consult your supervisor.

Orig. M. Loer 12-17-12

Pin Gages
Standard practice in American industry is to allow 5% of the product hole tolerance for
the GO gage tolerance and 5% for the NOGO gage tolerance. The GO gage, whose
nominal size is at the low limit of the hole to be checked is generally given a plus
tolerance in order to insure that all parts accepted fall within the product tolerance.

For the same reason the NOGO gage, whose nominal is at the high limit of the product
tolerance, is given a minus tolerance. In this age of strict product liability perhaps it is
better to reject a few acceptable parts than to pass any out-of-tolerance parts. The GO
gage plus tolerance and the NOGO minus tolerance have become universal in American
Industry and 10% of the hole tolerance - 5% at each end - is sacrificed to insure that
all pieces accepted are within tolerance.

Additional Notes about Pin Gage use:

 Holes to be gaged should be as clean as possible and free from burrs which
would interfere with insertion.
 The gage should of course be aligned with the hole for insertion; however, there
are some gage features which can aid in this. A chamfer or radius on the gage
end will help guide the gage into the hole. In addition, the GO gage may be
vented for gaging blind holes so the air pressure within the hole will not interfere
with the insertion of the gage.
 The gage should be turned into the work slowly and carefully. A good fit will be
snug. A plug gage should never be forced into a part.
 In using a NOGO gage you should be certain that the gage is truly unable to
enter the hole before the part is accepted. The procedure which is normally
made to insert the GO gage should be followed to insure that the NOGO gage is
being properly used.
 When gaging steel the temperature of a steel gage and the part should be the
same. Where the materials differ, however, such as tungsten carbide gage or a
non-steel part, consideration should be given to actual temperature since the
coefficients of expansion of the materials will differ. Standard temperature is 20
C (68 F). Gages are always calibrated at this temperature, and when the product
is also at this temperature accurate gaging is insured.
 Gages should be carefully protected against prolonged exposure to heat and
moisture. After cleaning gages should be oiled carefully with a rust inhibitor and
stored in containers or cases protected with rust inhibitor.
 Any program of gage use should include periodic inspection of the gages to
insure that they are not worn below tolerance or have otherwise become
scratched or marred. GO gages are, of course, subject to more wear and should,
therefore, be inspected more frequently. If a GO gage has worn below its
tolerance it will begin to accept undersized holes. Excess wear on the NOGO
gage, while not as common, will still interfere with the intended use of the gage.
The more the NOGO gage wears the more acceptable parts may be rejected.

Orig. M. Loer 12-17-12

 Unlike the GO gage, unacceptable parts will never be accepted; however, the
rejection of good parts may still be a costly price to pay for not having properly
checked the NOGO gage.

Ring and Plug Thread gages

Orig. M. Loer 12-17-12

Proper Care And Usage Of Gages

Part dimensions to be gaged should be cleaned and burr free to prevent gaging
interference. Grit and part chips which become lodged in thread gages will create
scratches and wear on the flanks of threads and on the outside and inside diameters of
cylindrical plain gages. Various materials such as aluminum and castings are extremely
abrasive and will tend to wear out gages more quickly than other types of materials.
Finer pitch and smaller diameter thread gages tend to wear quicker than larger and
coarser pitch gages and have less gage tolerance as well. Regarding thread gages, it
only takes a small amount of wear to have a significant effect on the pitch diameter.
The wear on each flank angle is multiplied by almost 4 times to determine the total
impact of wear on the pitch diameter. 50 microinches or 1 micron of wear per thread
flank will impact the measured size by .0002” which can be the total tolerance of many
thread gages.

Selecting higher precision gagemaker tolerances for cylindrical plug and ring gages will
consume less product tolerance and will allow the acceptance of slightly more product
but with less gage wear life and greater expense. The normal rule of practice requires
that 10% of part tolerance be divided between the Go and the No Go gages. Applying
this practice results in gage tolerance always being included in the part tolerance by up
to 10%.This could result in the possibility that 10% of good parts may fail inspection
but that no bad product would ever pass. Assuming that higher precision gagemaker
tolerances are better, is not valid, and may create quality issues as these gages tend to
wear quicker with the potential of becoming undersized and passing bad parts.

Gages should be turned or pushed slowly and gently into or onto the dimension being
checked. Forcing gages will result in faulty gaging and the possibility of damaging both
the part and gage. Spinning thread ring gages or thread plug gages onto or into parts
will create greater friction and increased wear thus reducing the life of the gage.

A thin coating of gage lubricant will help reduce friction from gage to part.

The effects of thermal expansion should be taken into consideration on both the part
and the gage.

The temperature of the part and the gage should be the same. 68° F is the ideal
temperature at which both part and gage should be at when inspected because gages
are calibrated at 68° F. This effectively eliminates any error due to thermal expansion.

Protecting gages from excessive heat, humidity, moisture and corrosive chemicals will
extend the life of your gages. After use, gages should be cleaned and recoated with a
thin-film rust preventative or dipped in an easy to peel oil-based waxed coating, and
stored properly.

Orig. M. Loer 12-17-12

Gages should be periodically inspected and calibrated to assure accuracy. Go member
gages tend to wear quicker with normal use. NOGO gages will wear on the ends that
receive the greatest usage. Frequency of inspection and calibration should be
dependent on such factors as the amount of usage, part and gage material, tolerance,
and quality procedures.

Profilometer

Orig. M. Loer 12-17-12

Measurement

1. Position the workpiece so that the measured surface is level.

2. Confirm the stylus is perpendicular and parallel to the measured surface.

3. Press the START/STOP key in the measurement mode.

4. The detector starts traversing to perform measurement.

5. While the measurement is being performed (detector is traversing), “------“ is

displayed on the LCD.

6. After the measurement has been completed, the measurement value will be
displayed.

7. The measurement value displayed will be Ra. To display other objective parameters
press the PARAMETER key until the desired parameter is displayed. Each time the key is
pressed, the displayed parameter changes in the following order: Ra->Ry->Rz->Rq-
>Ra

Calibration

Calibration is not normally required but if desired refer to the manual for proper
procedure.

Snap Gages

Orig. M. Loer 12-17-12

The principles of care and usage for these simple O.D. measuring tools are
straightforward. Because the body of the gage—the C-frame—is a rigid piece of metal,
most of the "care and feeding" tips are concerned with the gage's anvils. That's where
most of the precision lies.

Make sure the gage is suited to the application. The anvils should be narrower than the
part being measured to avoid uneven wear on the measuring surfaces. If you
repeatedly gage narrow parts on a broad anvil, you can wear grooves that may not be
picked up by mastering. You can get away with a small number of too-narrow parts,
but if you're doing a production run, buy different anvils or modify the existing ones.

Anvils can be straddle-milled or side-relieved to fit into grooves or recesses, or to

ensure they're narrower than the work piece. The edges can also be chamfered. This is
important when measuring a diameter immediately adjacent to a perpendicular feature
—for example, on a shaft. There's usually a fillet where two surfaces come together,
and if you put crisp, sharp-edged anvils right up against the perpendicular, you'll
measure the fillet instead of the critical dimension. Another way to phrase it is: Don't
check diameters next to perpendicular surfaces—unless you've got the right anvils.

Regularly check the anvils for wear. Look for scratches, gouges, unevenness, pitting,
rust, etc. If problems are detected, the anvils can be removed and their surfaces
ground and lapped. Check periodically that the anvils are parallel. This is essential if
you've removed the anvils for maintenance or replacement. To check for parallelism,
place a precision wire or a steel ball in sequence at the front, back, left and right edges
of the anvils. Compare the indicator reading for each of the edges.

If you detect an out-of-parallel condition and you haven't just replaced the anvils,
you've probably dropped the gage.

Orig. M. Loer 12-17-12

Observe the basics of good gaging practice: check regularly for looseness of
components, keep the gage clean, protect against rapid changes in temperature, and
master regularly. For large production runs, it makes sense to purchase a master disc
the size of your part. For small runs, use stacked gage blocks. Make sure you've wrung
them properly and observed the other basics of block care and usage.

Adjustments on indicating snap gages are few and simple. Set the backstop so the
diameter of the work piece is roughly centered on the anvils: it's not a critical
adjustment. To adjust the gage's capacity, turn the knurled nut that moves the upper
anvil/indicator assembly up or down. Move the upper anvil until the indicator zeroes
itself against the master. Then, before you tighten the locking nut(s), turn the adjusting
nut very slightly in the opposite direction to release the torque on the lead screw. This
may seem insignificant, but any amount of tension will relax itself over time. Then lock
it down, master the gage, and check for repeatability several times before you start
measuring.

Wide anvils normally ensure that the gage seats itself squarely on the part. But if you're
using narrow blade-type anvils to check narrow grooves, you have to hold the gage as
steady as you can, squaring it up by eye. Offset blade anvils also impose side-loading,
which can further reduce repeatability. To accommodate these shortcomings, lower-
resolution dial indicators are usually used with blade anvils: .005" resolution is typical,
compared to .0001" on most snap gages.

For large gages that weigh several pounds, the spring pressure on the upper anvil may
be insufficient to achieve repeatability in a hand-held situation. There's a simple
solution to this one: turn the gage upside down and allow the weight of the gage to
rest on the fixed anvil instead. Then just rotate the bezel on the dial indicator, so it
reads right-side up.

Orig. M. Loer 12-17-12