There are many types of tools used to measure and lay out projects. Measuring tools include flat steel rules, measuring tapes, wooden folding rules, digital measuring devices, and measuring wheels. Levels are used to check that project components are level and/or plumb. Plumb bobs are used to check that project components are perfectly upright. Squares are used to mark, check, and measure components of construction projects. When you consider which of these tools to use, keep in mind the following points: • The tool must be accurate.

In this unit, you will learn about different types of measuring and layout tools and their uses. You will also learn how to select the right tool for the  job, use and read various types of tools, and provide the proper care of the measuring and layout tools to keep them in good working condition.

When you have completed this unit, you will be able to:




Types and Uses

Dividers are instruments used for measuring distances between two points, transferring or comparing measurements directly from a rule, or for scribing an arc, radius, or circle.

Spring Divider

A spring divider consists of two sharp points at the end of straight legs, held apart by a spring and adjusted by means of a screw and nut. The spring divider is available in sizes from 3 to 10 inches in length.

Wing Divider

A wing-type divider has a steel bar that separates the legs, a lock nut for setting a rough measurement, and an adjustment screw for fine adjustments. The wing-type divider is available in 6, 8, and 12-inch lengths. Also available is a divider with one removable leg, so that a pencil may be inserted.


Using a Divider to Scribe a Circle

1. Set the desired radius on the dividers using the appropriate graduations on a rule
2. Place the point of one of the divider legs on the point to be used as the center.
3. Lean the dividers in the direction of movement and scribe the circle by revolving the dividers.

Care of Dividers

Observe the following guidelines when working with dividers:

• Keep dividers clean and dry.
• Protect the points against damage.
• Store dividers where they will not become bent or broken.


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Simple calipers are used in conjunction with a scale or rule to determine the thickness or the diameter of a surface, or the distance between surfaces. A caliper is usually used in one of two ways. Either the caliper is set to the dimension of the work and the dimension transferred to a scale, or the caliper is set on a scale and the work machined until it checks with the dimension setup on the caliper.

To adjust a caliper to a scale dimension, hold one leg of the caliper firmly against one end of the scale and adjust the other leg to the desired dimension. To adjust a caliper to the work, open the legs wider than the work and then bring them down to the work.

Outside Calipers

Outside calipers for measuring outside diameters are bowlegged; those used for inside diameters have straight legs with the feet turned outward. Calipers are adjusted by pulling or pushing the legs to open or close them. Fine adjustment is made by tapping one leg lightly on a hard surface to close them, or by turning them upside down and tapping on the joint end to open them.

Inside Calipers

Calipers used for inside diameters have straight legs with feet turned outward. Calipers are adjusted by pulling or pushing the legs to open or close them.

Transfer Calipers

Transfer calipers are used for measuring chamfered grooves or flanges. A screw attaches a small auxiliary leaf to one of the legs.

The measurement is made as with ordinary calipers. The leaf is locked to the leg. The legs may be opened or closed as needed to clear the obstruction. The legs are then brought back and locked to the leaf, restoring them to the original setting.

Hermaphrodite Calipers

Another type of caliper is the hermaphrodite, sometimes called the odd-leg caliper. This caliper has one straight leg ending in a sharp point, sometimes removable, and one bowleg. The hermaphrodite caliper is used chiefly for locating the center of a shaft, or for locating a shoulder.

Spring-Joint Calipers

Spring-joint calipers have the legs joined by a strong spring hinge and linked together by a screw and adjusting nut. For measuring chamfered cavities (grooves) or for use over flanges, transfer calipers are available. They are equipped with a small auxiliary leaf attached to one of the legs by a screw. The measurement is made as with ordinary calipers; then the leaf is locked to the leg. The legs may then be opened or closed as needed to clear the obstruction, and brought back and locked to the leaf again, thus restoring them to the original setting.

Slide Calipers

Slide calipers can be used for measuring outside and inside dimensions. Graduations are in inches, fractions, or millimeters. One side of the caliper is used to measure outside and the other side is used to measure inside dimensions. Stamped on the frame are the words “IN” and “OUT.” You use them when taking inside and outside measurements. The other side of the caliper is used as a straight measuring rule.


The trammel measures distances beyond the range of calipers. The instrument consists of a rule, rod, or beam to which trams are clamped. The trams carry chucks. The trammel can also be used as a divider by changing the points.

Vernier Calipers

Vernier calipers work like slide calipers. The vernier calipers can make very accurate outside or inside measurements. A vernier caliper is used by loosening the two locking screws, allowing the movable jaw to slide along the rule until desired position is obtained. The locking screw is then retightened securing the movable jaw. Any fine adjustments to the vernier scale are made using adjustment control. The locking screw is then secured and vernier caliper is ready to read.

Reading a Vernier Caliper

To read a vernier caliper (Figure 1), you must be able to understand both the steel rule and vernier scales. The steel rule is graduated in 0.025 of an inch. Every fourth division (representing a tenth of an inch) is numbered.

The vernier scale is divided into 25 parts and numbered 0, 5, 10, 15, 20, and 25. These 25 parts are equal to 24 parts on the steel rule. The difference between the width of one of the 25 spaces on the vernier scale and one of the 24 spaces on the steel rule is a thousandth of an inch.

Figure 1 — Reading a vernier caliper.

To read the measurement as shown in Figure 1:

  1. Read the number of whole inches on the top scale to the left of the vernier zero index and record: 1.000 inch.
  2. Read the number of tenths to the left of the vernier zero index and record: 0.400 inch.
  3. Read the number of twenty-fifths between the tenths mark and the zero index and record: 3 x .025 = .075 inch.
  4. Read the highest line on the vernier scale (3) that lines up with the lines on the top scale and record (Remember 1/25 = 0.001 inch): 11/25 or 0.011 inch.

TOTAL: 1.486 inches.

Most vernier calipers read outside on one side and inside on the other side. If a scale isn’t marked, and you want to take an inside measurement, read the scale as you would for an outside diameter. Then add the measuring point allowance by referring to manufacturer’s instructions. An example of the additional measurement allowance is illustrated in Table 1.

Table 1 — Additional measurement allowance

Size of Caliper English Measure (add) Metric Measure (add)
 6 inch or 150 mm

0.250 inch

6.35 millimeters (mm)

12 inch or 300 mm

0.300 inch

7.62 mm

24 inch or 600 mm

0.300 inch

7.62 mm

36 inch or 600 mm

0.500 inch

12.70 mm

Reading a Metric Caliper

The steel rule is divided into centimeters (cm) (Figure 2) and the longest lines represent 10 millimeters (mm) each. Each millimeter is divided into quarters. The vernier scale is divided into 25 parts and is numbered 0, 5, 10, 15, 20, and 25.

Figure 2 — Reading a vernier caliper.

Read the total number of millimeters to the left of the vernier zero index and record: 32.00 mm.

Read the number of quarters between the millimeter mark and the zero index and record: 0.25 mm (1 quarter).

Read the highest line on the vernier scale aligning with the line on the scale and record: 0.18 mm.

TOTAL: 32.43 mm.

Care of Calipers

Observe the following guidelines when working with calipers:


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Types and Uses

Micrometers are instruments used to measure distances to the nearest onethousandth of an inch. These measurements are expressed or written as a decimal (0.0001, 0.001, 0.01), so to use them you must know how to read and write decimals. There are four types of micrometer calipers, commonly called micrometers or simply mikes, used throughout the Navy: the outside micrometer, the inside micrometer, the depth micrometer, and the screw thread micrometer.

Common types of micrometers.

Outside Micrometers

The outside micrometer is used for measuring outside dimensions, such as the outside diameter of a piece of round stock or the thickness of a piece of flat stock, to an accuracy of 0.001 of an inch.

Inside Micrometers

Inside micrometers are used to measure an inside diameter to an accuracy of 0.001 of an inch. Inside micrometers have a range of 0.500 inch, when used with 1/2-inch spacers.

Depth Micrometers

Depth micrometers  are used to measure depths to an accuracy of 0.001 inches.

Screw Thread Micrometers

The screw thread micrometer is used to determine the pitch diameter of screws

Selecting the Proper Micrometer

The types of micrometers commonly used are made so that the longest movement that the micrometer spindle or rod can make is 1 inch. This movement is called the range; for example, a 2- inch micrometer has a range of from 1 to 2 inches, and can only measure work with a thickness or diameter within that range. A 6-inch micrometer has a range from 5 to 6 inches, and will measure only work between 5 and 6 inches thick. The frames of micrometers, however, are available in a wide variety of sizes, from 1 inch up to as large as 24 inches.

It is necessary, therefore, that the mechanic first find the approximate size of the work to the nearest inch, and then select a micrometer that will fit it. For example, to find the exact diameter of a piece of round stock, use a rule and find the approximate diameter of the stock. If it is found to be approximately 3 1/4-inches, a micrometer with a 3- to 4-inch range would be required to measure the exact diameter. Similarly, with inside and depth micrometers, rods of suitable lengths must be fitted into the tool to get the approximate dimension within an inch, after which the exact measurement is read by turning the thimble. The size of a micrometer indicates the size of the largest work it will measure.

Reading a Standard Micrometer

The sleeve and thimble scales of a micrometer (Figure 3) have been enlarged and laid out for demonstration. Reading a micrometer is only a matter of reading the micrometer scale or counting the revolutions of the thimble and adding any fraction of a revolution. To understand these scales, you need to know that the threaded section on the spindle, which revolves, has 40 threads per inch. Therefore, every time the thimble completes a revolution, the spindle advances or recedes 1/40 inch, or 0.025 inch.

Figure 3 — Sleeve and thimble scales of a micrometer.

Note the horizontal line on the sleeve is divided into 40 equal parts per inch. Every fourth graduation is numbered 1, 2, 3, 4, and so on, representing 0.100, 0.200, 0.300, and 0.400 inch, respectively. When you turn the thimble so its edge is over the first sleeve line past the 0 on the thimble scale, the spindle has opened 0.025 inch. If you turn the spindle to the second mark, it has moved 0.025 inch plus 0.025 inch, or 0.050 inch. When the beveled edge of the thimble stops between graduated lines on the sleeve scale, you must use the thimble scale to complete your reading. The thimble scale is divided into 25 equal parts; each part or mark represents 1 /25 of a turn; 1/25 of 0.025 inch equals 0.001 inch.

Note that in Figure 4 every fifth line on the thimble scale is marked 5, 10, 15, and so on. The thimble scale permits you to take very accurate readings to the thousandths of an inch.

Figure 4 — Enlarged micrometer scale.

The enlarged scale in Figure 4 can help you understand how to take a complete micrometer reading to the nearest thousandth of an inch.

The thimble is turned far enough to expose the 7 on the sleeve scale but not far enough to expose the first mark after the 7. Therefore, the measurement must be between 0.700 inch and 0.725 inch. Exactly how far between 0.700 inch and 0.725 inch must be determined from the thimble scale.

As you can see, the thimble has been turned through 12 spaces of its scale, and the 12th graduation is lined up with the reference line on the sleeve. When the value on the sleeve scale is added to the value on the thimble scale that is lined up with the reference line on the sleeve scale, the space between the anvil and spindle must be 0.712 inch (seven hundred twelve thousandths of an inch).


Keep the sleeve and thimble free of grease and dirt. Grease and dirt cause inaccurate readings on micrometers.

Reading a Vernier Micrometer

Many times you are required to work to exceptionally precise dimensions. Under these conditions it is better to use a micrometer that is accurate to tenthousandths of an inch. This degree of accuracy is obtained by the addition of a vernier scale.

The vernier scale of a micrometer (Figure 5) furnishes the fine readings between the lines on the thimble rather than requiring you to estimate the reading. The 10 spaces on the vernier are equivalent to 9 spaces on the thimble. Therefore, each unit on the vernier scale is equal to 0.0009 inch, and the difference between the sizes of the units on each scale is 0.0001 inch.

Figure 5 — Vernier scale of a micrometer.

When a line on the thimble scale does not coincide with the horizontal reference line on the sleeve, you can determine the additional spaces beyond the readable thimble mark by finding which vernier mark matches up with a line on the thimble scale. Add this number, as that many ten-thousandths of an inch, to the original reading.

In Figure 6, see how the second line on the vernier scale matches up with a line on the thimble scale. This line means that the 0.011 mark on the thimble scale has been advanced an additional 0.0002 beyond the horizontal sleeve line. When you add this number to the other readings, the reading is 0.200 + 0.075 + 0.011 + 0.0002, or 0.2862, as shown.

Figure 6 — Reading a vernier scale.

Reading a Metric Micrometer

Figure 7 — Metric micrometer.

The same principle is applied in reading the metric graduated micrometer (Figure 7), but the following changes in graduations are used:

The pitch of the micrometer screw is 0.05 mm. One revolution of the spindle advances or withdraws the screw a distance equal to 0.5 mm.

The barrel is graduated in millimeters from 0 to 25. It takes two revolutions of the spindle to move the barrel 1 mm.

The thimble is graduated in 50 divisions with every fifth line being numbered.

Rotating the thimble from one graduation to the next moves the spindle 1 /50 of 0.5 mm, or 1/100 mm. Two graduations equal 2/100 mm, and so forth.

The thimble is turned far enough to expose the 20 on the sleeve scale. The number of lines visible between the number 20 and the thimble edge is 2, which is equivalent to 2 mm. The line on the thimble coincides with the long line in the barrel, 36 or 0.36 mm. When you add the measurements together, the reading is 20 + 2 + 0.36, or 22.36 mm.


Remember that 1 revolution is 0.5 mm. It takes 2 revolutions to move 1 mm.

Care of Micrometers

Observe the following guidelines when working with micrometers:


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Types and Uses

The rule or tape is used for measuring where accuracy is not an extremely critical factor. They can be rigid or flexible, come in various lengths, and can be made of wood, metal, cloth, or fiberglass.


Steel rule

The flat steel rule is the simplest measuring tool. It is usually 6 or 12 inches in length but can be longer. Steel rules can be rigid or flexible, thin or wide. It is easier and more accurate to use a thin rule, since it is closer to the work being measured.

Flat steel rules can have up to four sets of marks, two on each side of the blade. Rules with four sets of marks are set up with divisions of 1/8 inch and 1/16 inch on one side, and divisions of 1/32 inch and 1/64 inch on the other side. The marks are longer for a division of 1/2 inch, scaling down in length from 1/4 inch through 1/64 inch.

There are many variations of the common rule. Sometimes the graduations are on one side only, sometimes a set of graduations is added across one end for measuring in narrow spaces, and sometimes only the first inch is divided into sixty-fourths, with the remaining inches divided into thirty-seconds and sixteenths. A metal or wood folding rule may be used.

Folding Rules

 A folding rule is made up of hardwood, steel, or aluminum sections, each measuring 6 to 8 inch. The sections are connected by spring joints that unfold for measuring distances. These folding rules are usually from 2 to 6 feet long. The folding rules cannot be relied on for extremely accurate measurements because a certain amount of play develops at the joints after continued use.

Measuring Tapes

A measuring tape can come in any length from 6 to 50 feet. The most common are 10, 16, and 25 feet. Shorter tapes usually have a curved cross section so they roll easily but stay rigid when extended. Longer tapes are usually flat and should be laid along a surface to avoid sagging in the middle. A locking mechanism, such as a sliding button, keeps the tape locked in place while a measurement is being taken. Other locking mechanisms, such as levers and toggles, allow the tape to be retracted after measuring by simply squeezing them. In any case, a spring mechanism in the case automatically retracts the tape.

How to Use a Measuring Tape. Follow these steps to use a measuring tape properly:

1. Pull the tape out to the desired length.

2. Place the hook over the edge of the material you are measuring.

3. Lock the tape in place.

4. Record or mark the measurement.

5. Unhook the tape from the edge of the material.

6. Release the lock and rewind the tape

Digital Measuring Devices

Digital measuring devices are similar to conventional measuring devices, but their digital readouts make measurement readings more precise. They give you the ability to convert fractions to decimal or metric equivalents. A useful function of these devices is their ability to compensate for the size of the tape case when making measurements inside a window frame or door jamb. Some devices have a memory function that holds a measurement; others have a voice recorder to keep track of multiple measurements.

Measuring Wheel

A measuring wheel is made up of a wheel, handle, odometer, and a reset button to return the counter to zero. It is designed to take lengthy exterior measurements, as long as 10,000 feet. Measuring wheels can have collapsing or telescoping handles, different tread materials, and optional storage cases. Wheel diameters range from 4 to 25 inches, with the larger wheels suitable for rough terrain.

Care of Rules and Tapes

Observe the following guidelines when working with rules and tapes: For all measuring tools • Always wear eye protection when using measuring tools.

For wooden folding rules:  Maintain a wooden folding rule by occasionally applying a few drops of light oil on the spring joints.


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Types and Uses

Parts of a level.

Levels are tools designed to prove whether a plane or surface is in the true vertical or true horizontal. All levels consist of a liquid-filled glass tube or tubes supported in a frame.

Master Precision Level

The master precision level has a ground and graduated main vial. The top and bottom of the level are milled and ground to make sure both surfaces are absolutely parallel. This level is used to determine the true horizontal with the main vial. The true vertical is determined by using the two smaller vials.

Machinist’s Level

The machinist’s level has an extra-large vial, increasing the accuracy and sensitivity. Some of these levels have grooved bottoms which fit over pipes and shafts. They are used in machine shops for leveling work and equipment.

Iron Bench Level

The iron bench level is made of a special design casting which ensures its lightness, strength, and rigidity. It is used mostly in the construction industry. It may also be used in a machine shop

Striding Level

The striding is a machinist’s level which is mounted on a raised base. This level is used to span existing cabling, piping, or similar obstructions. It is extremely useful in a machine shop for checking the true horizontal of the flatway on a lathe.

Carpenter’s Level

The carpenter’s level  has three vials which are mounted horizontally, vertically, and at a 45-degree angle. The carpenter’s level is used in construction for checking for true vertical, true horizontal, and 45-degree angles.

Line Level

The line level is a single vial in a metal case with a hook on each end for hanging on a cord. It is used to check whether two points are level, such as two points on a floor or in an elevation. It must be used with a tightly stretched cord.

Torpedo Level

The torpedo level is a small level, generally 6 to 9 inches in length. Its name is derived from its boat-like shape, tapered at both ends. It is useful in small spaces where a larger level would not fit.

Digital Level

The digital level has two vials; one to check for level, the other to check for plumb. It also includes a digital readout for:

Laser Level 

A laser level is used to level and provide reference lines for tasks such as setting foundation levels, establishing drainage slopes, aligning plumbing and electrical lines, and setting tile. It can be mounted on a tripod, fixed to pipes or framing studs, or suspended from ceiling framing.

Using a Level

A level may be checked for accuracy by placing it on a known level surface and noting the position of the bubble. Reverse the level end for end. Observe the position of the bubble. If the relative position of the bubble was the same for both readings, the level is accurate.

The carpenter and torpedo levels are easy to use. All you need is a careful eye to read it correctly.

  1. Place the level on the object you need to check. Lay it on a horizontal surface or hold it against a vertical surface.
  2. Check the air bubble in the vial. When the bubble is centered between the two lines on the vial, the object you are checking is level if you are checking a horizontal surface, plumb if you are checking a vertical surface, or at a 45-degree angle if you are checking the angle.

Care of Levels

You are not likely to have any personal injuries from using a level. However, you can damage this sensitive instrument if you don’t handle it carefully.

Observe the following guidelines when working with levels:


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Types and Uses

A plumb bob is a precision instrument used to establish a true vertical transfer and line-up reference point, and to take readings or soundings in tanks and voids. Plumb bobs are used by carpenters, surveyors, and maintenance technicians.

Surveyor's Polished Brass

The surveyor’s brass plumb bob may be either a spool type or an adjustable cap type. Both types have replaceable steel points for increased accuracy. The adjustable cap allows the operator to make minor corrections to height and rotation to make sure the bob hangs straight. The surveyor’s brass plumb bob comes with a minimum of 7 feet of nylon, silk or linen cord. It comes in 6-, 8-, 10-, and 16-ounce sizes. The heavier plumb bobs are better for use in windy areas.

Solid Steel

The solid steel plumb bob may have a machined integral head, body, and point. It may have just a removable head, or a removable head and a replaceable point. It may be round or hexagonal in shape and it comes in 3-, 8-, and 12- ounce sizes. Cord for the solid steel bobs must be obtained from a separate source. This type plumb bob is used when extreme accuracy is not required.

Using a Plumb Bob

  1. The practice procedure which follows (for establishing the true vertical of a post) uses a plumb bob with a removable head.
  2. The following task is not the only use of a plumb bob.
  3. Post hole must be dug and an assistant is required before starting the task.

Follow these steps to use a plumb bob properly:

  1. The first step is to attach the cord as follows:
  2. Insert a string or cord into the cap (Figure 8) of the plumb bob. Make sure the cord will support the plumb bob. Pull the cord through the cap.

Figure 8 — Insert a string.

Figure 9 — Overhand knot.

  1. Place cap in the palm of your hand and tie an overhand knot (Figure 9) in the cord. Pull the cord, drawing the knot against cap base. Make sure the knot is not too large or tied at an angle, which would affect the hanging of the plumb bob.
  2. Install cap into plumb bob body (Figure 10).

Figure 10 — Install the cap.

  1. Tighten cap securely in the body and suspend the plumb bob by the cord only. Make sure the knot will support the plumb bob.
  2. Place a ruler on the top of the post so that it extends 2 inches beyond an edge.
  3. Position the string and plumb bob so they extend over end of ruler (Figure 11) and the plumb bob is just above the ground surface.
  4. Have the assistant measure distance from post to string just above the plumb bob (Figure 12). It should read 2 inches. If it doesn’t, move the base or the top of the post right or left until you achieve a 2-inch reading on both rules.

Figure 11 — Position the plumb bob.

Figure 12 — Measure the distance..

Figure 13 — Measuring at the point.

  1. Have the assistant measure distance from post to string just above the plumb bob (Figure 13). It should read 2 inches. If it doesn’t, move the base or the top of the post right or left until you achieve a 2-inch reading on both rules.
  2. When extreme accuracy is desired, measurement would be taken to the point of the plumb bob (Figure 13).
  3. Repeat steps 5, 6, and 7 on the other edge of the post.


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Types and Uses

Machinist’s scribers.

Use the machinist’s scribers to mark or score on steel, glass, aluminum, copper, or other similar surfaces. There are two basic types of machinist’s scribers, single point pocket and bent point-straight point. The single point scriber is used to mark the lines on the material. The bent point is used to scribe through holes or other hard to reach places. The tips have extremely hard points, usually made of tungsten carbide, and are used on hardened steel or glass.

Using a Machinist’s Scriber

Figure 14 — Scribing a line.

Follow these steps to use a machinist’s scriber properly:

  1. Place material to be marked on a firm surface. Place a steel rule or straight edge on the work beside the line to be scribed (Figure 14).
  2. Use fingertips of one hand to hold the straight edge securely. Hold the scriber in your hand as you would a pencil.
  3. Scribe the line by drawing the scriber along the straight edge at a 45-degree angle and tipped in the direction it is being moved.

Care of Scribers

Observe the following guidelines when working with scribers:


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Types and Uses

Carpenter’s Square

The carpenter square, has a large arm, called the blade, and a small arm, called the tongue. The arms meet in a 90-degree angle. The square is used to mark, check, and measure components of construction projects. It has several scales etched onto the surface for quick reference: a diagonal scale, a board foot scale, and an octagonal scale. It has ruler increments etched on the inside and outside edges.

The face side contains the manufacturer’s name and the inches are divided into eighths and sixteenths (Figure 15). There are two tables down the center.

Figure 15 — Parts of a carpenter’s square.

The rafter table is used for determining the length and cut of rafters.

The octagon or eight square scale is used for cutting an octagon from a square piece of material.

The back side contains the hundredths scale and is divided into tenths, twelfths, and sixteenths as shown. There are two tables down the center.

The Essex board measure is used to compute the number of board feet in a given piece of lumber.

The brace measure is used to find the exact lengths of common braces.

Common scales or inch divisions found on the carpenter’s square are listed in Table 2.

Table 2 — Scales and measurements of a carpenter’s square

Try Square

 The try square is an L-shaped tool used as a guide to lay out 90 degree cuts with pencil markings. It is also used to check that the edges and ends of boards are square, and whether a board is the same depth along its entire length. A try square has broad blades 6 to 12 inches long set at right angles.

Combination Square

Figure 16 — Combination square.

The combination square (Figure 16) is used for many purposes in woodworking and metalworking but mainly for measuring the accuracy of a right angle. It is made up of the following components:

  1. A slotted 12-inch stainless steel rule which is graduated in eighths, sixteenths, thirty-seconds, and sixty-fourths of an inch. It can be used as a measuring scale by itself or with any one of the following components.
  2. The center head, when attached to the rule, bisects a 90-degree angle. It’s used for determining the center of cylindrical work.
  3. The protractor has a level and a revolving turret which is graduated in degrees from 0 to 180 or 0 to 90 in either direction. It is used to lay out and measure angles to within 1 degree.
  4. The square head has a level, a scribe, and 45- and 90-degree sides. It is used to lay out 45- and 90-degree angles and to check level. It may also be used as a height or depth gage.

Sliding T-Bevel

The sliding T-bevel is made up of a slotted blade and a solid stock. The blade is adjustable so it can be set to measure any angle. The T-bevel is used for testing bevels and laying out angles.

Bevel Protractor

The bevel protractor is made up of an adjustable blade and a graduated dial which contains a vernier scale. The bevel protractor is used to establish an angle and determine its relationship to other surfaces. The acute angle attachment is used for measuring acute angles accurately.

Rafter Angle (Speed) Square

The rafter angle square or speed square is a three-sided, triangle shaped measuring tool. It is used to draw perpendicular lines on boards to be cut, or to lay out angles for rafters, stairs, and other construction projects. It has degree gradations etched onto the surface for quick layout and cutting of lumber so you don’t have to perform angle


The T-square is used to measure and cut drywall. Some table saws come with a T-square fence attached.

Using a Carpenter’s Square to Mark a Square Line

To mark a line for cutting, use the following steps:

  1. Find and mark where the line will be drawn.
  2. Line the square up with the bottom of the object to be marked as shown in Figure 17.
  3. Mark the line to be cut; mark an x on the material to be cut away.
  4. Cut off the excess material.

Figure 17 — Using a carpenter’s square.

Check that joints meet at a 90-degree angle by placing the blades of the framing square along the two sides of the angle, as shown in Figure 18. If both blades fit tightly, the material is square. If there is any space between either of the arms and the side closest to it, the material is not square.

Figure 18 — Checking for square


Using a Carpenter’s Square to Lay out Steps

Figure 19 — Square position for steps.

  1. An example to properly position a square when marking cut lines for a series of steps 9 inches by 12 inches is illustrated in Figure 19.
  2. Continue the process until desired number of steps has been laid out.

Using a Sliding T-Bevel Square

Follow these steps to use a sliding T-bevel properly:

Figure20 — Set the sliding T-bevel.

  1. Loosen the locking nut and adjust blade to measure a desired angle using a protractor (Figure 20). Tighten the locking nut.
  2. The angle may now be laid out by extending the blade across the board with the stock (Figure 21) held firmly against the edge.
  3. Mark with a pencil or marking crayon. Make sure the square does not move while marking (Figure 22).

Figure 21 — Transfer the angle to the material.

Figure 22 — Mark the angle.


Using a Combination Square

Follow these steps to use a combination square properly:

Using as a Center Head to Find the Diameter of a Cylinder

Figure 23 — Set the combination square.

  1. Slide center head on rule and fasten by tightening setscrew (Figure 23).
  2. Put the center head flush against the cylinder (Figure 24).
  3. Mark the diameter on the cylinder (Figure 25) using a pencil or marking crayon by drawing a straight line along the inside edge. Make sure the square does not slip while marking.

Figure 24 — Press against the cylinder.

Figure 25 — Mark the diameter.

Using as a Protractor Head to Determine an Angle

Figure 26 — Set up the combination square.

Figure 27 — Measure the angle.

  1. Slide protractor head on rule (Figure 25) and fasten by tightening setscrew.
  2. Loosen the protractor adjustment screws so the protractor may be pivoted about the rule. Angle being measured is already marked.
  3. Place the rule on the angle being measured (Figure 27) and pivot the protractor head against the edge. Tighten adjustment screws.
  4. Remove and read the measured angle on the protractor scale (Figure 26).

Figure 28 — Verify the angle.

Using a Combination Square to Mark 90-Degree and 45-Degree Angles

Mark a 90-degree angle (Figure 29) using the following steps.

  1. Set the blade at 90 degrees (a right angle).
  2. Place the square so the head fits snugly against the edge of the material to be marked.
  3. Use the blade as a straightedge to guide the mark, starting at the edge of the material.

Figure 20 — Mark a 90-degree cut with a combination square.

Figure 30 — Mark a 45-degree cut with a combination square.

Mark a 45-degree angle (Figure 30) using the following steps.

  1. Set the blade at a 30-degree angle.
  2. Place the square so the head fits snugly against the edge of the material to be marked.
  3. Use the blade as a straightedge to guide the mark, starting at the edge of the material.

Care of Squares

Observe the following guidelines when working with squares:


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Types and Uses

Surface Gage

A surface gage is a measuring tool used to transfer measurements to work by scribing a line, and to indicate the accuracy or parallelism of surfaces. The surface gage consists of a base with an adjustable spindle to which may be clamped a scriber or an indicator.

Surface gages are made in several sizes and are classified by the length of the spindle. The smallest spindle is 4 inches long, the average 9 to 12 inches, and the largest 18 inches. The scriber is fastened to the spindle with a clamp. The bottom and the front end of the base of the surface gage have deep V-grooves. The grooves allow the gage to measure from a cylindrical surface.

The base has two gage pins. They are used against the edge of a surface plate or slot to prevent movement or slippage.

Rule Depth Gage

A rule depth gage measures the depth of holes, slots, counterbores, and recesses. Some rule depth gages can also be used to measure angles. This measurement is done by using the angle marks located on the sliding head. The rule depth gage is a graduated rule with a sliding head designed to bridge a hole or slot. The gage holds the rule at a right angle to the surface when taking measurements. This type has a measuring range of 0 to 5 inches. The sliding head has a clamping screw so that it may be clamped in any position. The sliding head is flat and perpendicular to the axis of the rule. It ranges in size from 2 to 2 5/8 inches wide and from 1/8 to 1/4 inch thick.

Micrometer Depth Gage

The micrometer depth gage consists of a flat base that is attached to the barrel of a micrometer head. These gages have a range from 0 to 9 inches, depending on the length of extension rod used. The hollow micrometer screw has a 1/2- or 1- inch range. Some are provided with a ratchet stop. The flat base ranges in size from 2 to 6 inches. Several extension rods are supplied with this type gage.

Vernier Depth Gage

The vernier depth gage consists of a graduated scale either 6 or 12 inches long. It also has a sliding head similar to the one on the vernier caliper.

The sliding head is designed to bridge holes and slots. The vernier depth gage has the range of the rule depth gage. It does not have quite the accuracy of a micrometer depth gage. It cannot enter holes less than 1/4 inch in diameter. However, it will enter a 1/32-inch slot. The vernier scale is adjustable and may be adjusted to compensate for wear.

Dial Depth Gage

Dial depth gages are for rapidly checking depths of holes, recesses, slots, scratches, and paint thicknesses. It should be noted that measurements made with depth gages should be on a longitudinal axis. The depth gage will give direct readings on the dial in half-thousands of an inch (0.0005 inch); press the push button down until the measuring rod contacts the work and read the depth on the dial.

Height Gage

A height gage is used in the layout of jigs and fixtures. On a bench, it is used to check the location of holes and surfaces. It accurately measures and marks off vertical distances from a plane surface. The vernier height gage is a caliper with a special base to adapt it for use on a surface plate. Height gages are available in several sizes. Most common are the 10-, 18-, and 24-inch gages in English measure. The most common metric gages are the 25- and 46-centimeter sizes. Height gages are classified by the dimension they will measure above the surface plate. Like the vernier caliper, height gages are graduated in divisions of 0.025 inch. Its vernier scale is divided into 25 units for reading thousandths of an inch.

Surface Plate

Surface plate

A surface plate provides a true, smooth, plane surface. It is often used as a level base for surface and height gages from which to make accurate measurements. Surface plates are usually made of close grained cast iron, are rectangular in shape, and come in a variety of sizes.

Using the Surface, Depth, and Height Gages

Follow these steps to use surface, depth, and height gages properly:

Surface Gage

Using a surface gage.

Setting the surface gage to transfer a 4-inch vertical measurement.

Rule Depth Gage

Using a rule depth gage

Above is a method of using a rule depth gage to measure the distance from a surface to a recessed point.

Micrometer Depth Gage

Using a micrometer depth gage

An example of measuring projection depth with micrometer depth gage.

Vernier Depth Gage

Using a vernier depth gage

Using a vernier depth gage to measure the depth of a hole from a given surface is illustrated.

Dial Depth Gage

Measuring depths of holes, recesses, slots, scratches, and paint thicknesses with a dial depth gage is illustrated.

Using a dial depth gage

Height Gage

Using a height gage

Using a height gage to measure a vertical distance from a plane surface is shown above.

Care of Surface, Height, and Depth Gages

Observe the following guidelines when working with surface, height, and depth gages:


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Types and Uses

Ring and snap gages and precision gage blocks are used as standards to determine whether or not one or more dimensions of a manufactured post are within specified limits. Their measurements are included in the construction of each gage, and they are called fixed gages. However, some snap gages are adjustable. Gages are used for a wide range of work, from rough machining to the finest tool and die making. The accuracy required of the same type of gage will be different, depending on the use.

The following classes of gages and their limits of accuracy are standard for all makes:

A listing of tolerances for ring gages in each class is illustrated in Table 4-3.

Table 4-3 — Ring gages in each class

        Ring Gages

The plain ring gage is an external gage of circular form. For sizes between 0.059 and 0.510 inch, ring gages are made with a hardened bushing pressed into a soft body. The thickness of the gage will range from 3/16 to 1 5/16 inches. On ring gages, the GO gage is larger than the NO GO gage.

The GO and NO GO ring gages are separate units. They can be distinguished from each other by an annular groove cut in the knurled outer surface of the NO GO gage. Ring gages made for diameters of 0.510 to 1.510 inches are the same as those shown above, except there is no bushing; they are made all in one piece. Ring gages sized from 1.510 to 5.510 inches are made with a flange. This design reduces the weight, making the larger sizes easier to handle.

Ring gages are used more often in the inspection of finished parts than parts in process. The reason for measuring the final part is that the parts are usually readily accessible, whereas parts in a machine that are supported at both ends would have to be removed to be checked.

Snap Gages

The plain snap gage is made in two general types, the nonadjustable and adjustable. The nonadjustable type is a solid construction, having two gaging members, GO and NO GO. The part to be inspected is first tried on the GO side and then the gage is reversed and the part tried on the NO GO side. Some solid snap gages have combined gaging members in the same set of jaws as shown above, known as a progressive snap gage. The outer member gages the GO dimension and the inner member the NO GO dimension.

Three standard designs of the adjustable type are available, consisting of a light, rigid frame with adjustable gaging pins, buttons, or anvils. These pins or buttons may be securely locked in place after adjustment, and locking screws are tightened to hold the gaging dimensions. One type of adjustable snap gage is made in sizes that range from 1/2 to 12 inches. It is equipped with four gaging pins and is suitable for checking the dimension between surfaces. Another type is made in sizes that range from 1/2 to 11¼ inches. It is equipped with four gaging buttons and is suitable for checking flat or cylindrical work. The third type is made in sizes from 1/2 to 11 5/8 inches. It is equipped with two gaging buttons and a single block anvil, and is especially suitable for checking the diameters of shafts, pins, studs, and hubs.

Gage Blocks

Gage blocks are available in sets of from 5 to as many as 85 blocks of different dimensions. Precision gage blocks are made from a special alloy steel. They are hardened, ground, and then stabilized over a period of time to reduce subsequent waxing. They are rectangular in shape with measuring surfaces on opposite sides. The measuring surfaces are lapped and polished to an optically flat surface and the distance between them is the measuring dimension. This dimension may range from 0.010 inch up to 20 inches.

Using a Ring Gage

To check the shank diameter of a pivot stud, use the following steps (Figures 31 and 32):

  1. Line the stud up with the hole and press in gently. If the stud will not go in, the shank is too large. If it will go in, the stud is not oversize.
  2. With the stud in the hole, check the piece for taper and out-of-roundness by sensing any wobble.
  3. After checking the part in the GO gage, check it in the NO GO gage. The stud must not enter this gage to establish it as being between the desired limits.

Figure 31 — Align the ring gage to the stud.

Figure 32 — Check the NO GO gage.


The GO ring gage controls the maximum dimension of a part and NO GO plug gage controls the minimum dimension of a hole. Therefore, GO gages control the tightness of fit of mating parts and NO GO gages control the looseness of fit of mating parts

Using an Adjustable Snap Gage

Before an adjustable snap gage can be used to check parts, the GO and NO GO buttons, pins, or anvils must be set to the proper dimensions.

  1. The snap gage must first be clamped in a holder (Figure 4- 84).
  2. Loosen the locking screw and turn the adjusting screws until the dimension is set (Figure 4-85).
  3. Turn the other adjusting screw until the NO GO dimension is set.
  4. After adjusting for proper dimensions with the master precision piece in place, tighten the locking screws (Figure 4-86).
  1. Adjust the GO dimension first as shown in the illustration, or if desired, reverse the procedure and adjust the NO GO dimension first.
  2. The desired dimension may be taken from a master disk, a precision gage block, or a master plug.
  1. Recheck to make sure the dimensions have not changed before using the gage

Gaging Flat Parts

  1. Position the gage (Figure 33) so the pins or buttons are square with the flat surfaces on the part.
  2. Using a slight hand pressure, push the gage over the part (Figure 34).

Figure 33 — Position the snap gage.


Figure 34 — Gage the part.

  1. If the part is within limits (Figure 35), the NO GO pins will stop the part.
  2. If the part is undersized (Figure 36), it will be possible to push it past the NO GO pins

Figure 35 — Part within limits

Figure 36 — Part is undersized.

Gaging Cylindrical Parts

  1. Locate the gage on the part with the solid anvil on top. Rock the gage as indicated by the shaded segment in Figure 37, where the GO dimension is checked.
  2. If the shaft is not oversized, the first button will pass over it easily (Figure 38).

Figure 37 — Position the snap gage.

Figure 38 — Gage the part

  1. Move the gage to the position shown in Figure 39. If the NO GO button stops the gage, the shaft is within limits.
  2. If the gage can be rocked further to the position shown in Figure 40, the part diameter is too small, since it has passed the NO GO button.

Figure 39 — Part within limits

Figure 40 — Part is undersized.

Using Precision Gage Blocks

Before using gage blocks, remove the coat of rust preventive compound with a chamois or a piece of cleansing tissue or by cleaning with an approved solvent. Gage blocks and any measuring tool used with them must be free of grease, oil, dirt, and other foreign matter to avoid a lapping action whenever the block is moved, and to ensure accurate measurement. Take particular care when using gage blocks to measure hardened work to avoid scratching the measuring surfaces.


When building gage blocks (wringing them together) to obtain a desired dimension, care should be exercised to avoid damaging them.

  1. Bring the blocks together flat and move them slightly back and forth . The sliding motion minimizes scratching, as it will detect any foreign particles between the surfaces.
  2. Shift the blocks. If the blocks are clean, they will begin to take hold.
  3. Slide the two blocks together, using a slight pressure and a rotary motion.
  4. Shift gage blocks so that their sides are in line. Any combination of gage blocks may be stacked together in this manner. The combination will be as solid as a single block.



When building gage blocks (wringing them together) to obtain a desired dimension, care should be exercised to avoid damaging them.



Do not leave blocks wrung together for long periods of time since surfaces in contact will tend to corrode.

Factors to Consider

When Using Gage Blocks Ordinary changes in temperature have a sizable effect on measurements made with precision gage blocks. The standard measuring temperature is 68 degrees Fahrenheit (°F), which is just a little lower than the average temperature in most shops. Since the room temperature affects the work as well as the block, the expansion in the work will be matched in most cases by a similar expansion in the block. The coefficient of linear expansion of several metals and blocks is listed in Table 4-4.

Table 4-4 — Linear expansion of metals


Avoid conducting body heat into the block by careless handling. Body heat may raise the temperature of the block, causing a serious error in a measurement, particularly if a long stack of blocks is being handled.

Consider the source of error resulting from temperature when using gage blocks. Metals other than iron and steel (such as aluminum) have a much different coefficient of linear expansion, which will result in a difference between the room temperature measurement and the standard measuring temperature measurement. Careless handling of gage blocks may produce an error of several millionths of an inch and this error increases proportionally with the dimension of the block.

The temperature of the work may be either lower or higher than the room temperature as a result of a machining operation and this difference may be sufficient to cause a sizable error.

Theoretically, the measuring pressure should increase proportionally with the area of contact. For practical purposes, it is better to use a standard measuring pressure. The most commonly used pressure is 1/2 to 2 pounds.

Gage blocks are used in the layout and in checking the accuracy of tools, dies, and fixtures. They are also used in machine setups and in checking parts in process of manufacture and finished parts.

Gage blocks are commonly used in setting adjustable instruments and indicating gages and verifying inspection gages. Gage blocks are used to verify the accuracy and wear of ring and snap gages and many other special-purpose gages. The classification of blocks depends largely on the accuracy required. Typical classification is shown in Table 4-5.

 Table 4-5 — Typical classifications

Care of Ring and Snap Gages

Observe the following guidelines when working with ring and snap gages:

Care of Gage Blocks

 Observe the following guidelines when working with gage blocks:


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Types and Uses

Thickness (Feeler) Gages

Thickness (feeler) gagesare made in many shapes and sizes; usually 2 to 26 blades are grouped into one tool and graduated in thousandths of an inch.

Most thickness blades are straight, while others are bent at the end at 45-degree and 90-degree angles. Some thickness gages are grouped so that there are several short and several long blades together. Thickness gages are also available in single blades and in strip form for specific measurements. For convenience, many groups of thickness gages are equipped with a locking screw in the case that locks the blade to be used in the extended position.

These gages are fixed in leaf form, which permits the checking and measuring of small openings such as contact points, narrow slots, and so forth. They are widely used to check the flatness of parts in straightening and grinding operations and in squaring objects with a try square.

Center Gage

The center gage is graduated in fourteenths, twentieths, twenty-fourths, and thirtyseconds of an inch. The back of the center gage has a table giving the double depth of thread in thousandths of an inch for each pitch. This information is useful in determining the size of tap drills. Sixty-degree angles in the shape of the gage are used for checking Unified and American threads as well as for older American National or U.S. Standard threads and for checking thread cutting tools.

Screw Pitch Gages

Screw pitch gages are made for checking the pitch of U.S. Standard, Metric, National Form, V-form, and Whitworth cut threads. These gages are grouped in a case or handle, as are the thickness gages. The number of threads per inch is stamped on each blade. Some types are equipped with blade locks. The triangular shaped gage has 51 blades covering a wide range of pitches, including 11 1/2 and 27 threads per inch for V-form threads. Screw pitch gages are used to determine the pitch of an unknown thread. The pitch of a screw thread is the distance between the center of one tooth to the center of the next tooth.

Small Hole Gage Set

Small hole gages are adjustable, having a rounded measuring member. A knurled screw in the end of the handle is turned to expand the ball-shaped end in small holes and recesses. A micrometer caliper is used to measure the ball end. Maximum measuring capacity is 1/2 inch. This set of four or more gages is used to check dimensions of small holes, slots, grooves, and so forth from approximately 1/8 to 1/2 inch in diameter.

Telescoping Gages

Telescoping gages are used to gage larger holes and to measure inside distances. These gages are equipped with a plunger that can be locked in the measuring position by a knurled screw in the end of the handle. Maximum measuring capacity is 6 inches. Measurements must be calipered on the gage by a micrometer, as in the case of the small hole gages. They are also used when measurements cannot be taken with a standard micrometer. Telescoping gages are particularly adaptable for roughly bored work and odd sizes and shapes of holes. Compress the plungers and lock them by turning the handle screw.

Thread Cutting Tool Gages

Thread cutting tool gages are hardened steel plates with cutouts around the perimeter. Each cutout is marked with a number that represents the number of threads per inch.

These gages provide a standard for thread cutting tools. They have an enclosed angle of 29 degrees and include a 29-degree setting tool. One gage furnishes the correct form for square threads and the other for Acme standard threads.

Fillet and Radius Gages

The blades of fillet and radius gages are made of hard rolled steel. The double-ended blades of the gage have a lock which holds the blades in position. The inside and outside radii are on one blade on the gage. Each blade of each gage is marked in sixty-fourths. Each gage has 16 blades.

Drill Point Gage

The drill point gage consists of a 6-inch hook rule with a 59 degree sliding head that slides up and down the rule. The sliding head can be locked at any position on the rule and is graduated in thirty-seconds of an inch. This gage is used to check the accuracy of drill cutting edges after grinding. It is also equipped with a 6-inch hook rule. This tool can be used as a drill point gage, hook rule, plain rule, and a slide caliper for taking outside measurements.

Wire Gages

A wire gage is circular in shape with cutouts in the outside edge. Each cutout gages a different size wire, from 0 to 36 of the English Standard Wire Gage. A separate gage is used for American standard wire and another for U.S. Standard sheet and plate iron and steel.

Similar gages are also used to check the size of hot and cold rolled steel, sheet and plate iron, and music wire.

Drill Gages

The twist drill and drill rod gage has a series of holes with size and decimal equivalents stamped adjacent to each hole. One gage measures drill sizes numbers 1 to 60; the other gage measures drill sizes 1/16 to 1/2 inch in 1/64-inch intervals. Drill gages determine the size of a drill and indicate the correct size of drill to use for given tap size. Drill number and decimal size are also shown in this type gage. Letter size drill gages are also available. Each drill hole is identified by a letter instead of a number, decimal, or fraction.

Marking Gages

Marking gages are made of wood or steel. They consist of a graduated beam about 8 inches long on which a head slides. The head can be fastened at any point on the beam with a thumbscrew. The thumbscrew presses a brass shoe tightly against the beam and locks it firmly in position. A steel pin or spur marks the wood and projects from the beam about 1/16 inch. A marking gage is used to mark off guidelines parallel to an edge, end, or surface of a piece of wood. It has a sharp spur or pin that does the marking. A marking gage must be adjusted by setting the head the desired distance from the spur.

Adjustable Parallel

Adjustable parallels consist of two tapered parts fitted together. The distance between the two outside parallel surfaces varies by moving mating parts together or apart. This distance is then measured with a micrometer. Adjustable parallels are used as gages for leveling and setup work. Various sizes are available depending on the nature of work.

Angle Plates

Angle plates are devices consisting of two flat outside working surfaces jointed at right angles. The outside work surfaces are precision ground. The standard angle plate is permanently jointed at a right angle. However, an adjustable type with varying angle adjustments is also available. Angle plates are used for layout, inspection, or machine setup. They are also used for clamping or holding work vertically. Various sizes and designs are available depending on the task.

Magnetic Base

Indicator Holder The magnetic base indicator holder is a one-piece metal assembly that attaches to the work surface magnetically. A gage or indicator attaches to the assembly. Base indicator holders are used for attaching gages to lathes, milling machines, shapers, or any machine where graduations are difficult to read. Magnetic base indicator holders are available in many sizes and designs depending on application.

Using Gages

Follow these steps to use gages properly:

Thickness Gage

Thickness (feeler) gages are used in one of two ways: as a means for determining a measure or a means for adjusting to a definite limit (Figure 41). A thickness gage is used to check piston ring gap clearance in a cylinder bore.

Figure 41 — Using thickness (feeler) gages.

A long blade thickness gage is used to determine the fit between large mating surfaces. By combining blades it is possible to obtain a wide variation of thickness.

Center Gage

The center gage is used to set thread cutting tools. Four scales on the gage are used for determining the number of threads per inch. The gage is also used to check cut threads and the scales are used to measure threads per inch.

Screw Pitch Gage

If the pitch of a thread is not known, it can be determined by comparing it with the standards on the various screw pitch gages (Figure 42).

Figure 42 — Using a screw pitch gage.

  1. Place a blade of a gage over the threads and check to see whether it meshes; if not, successively check each blade of the gage against the thread until it meshes.
  2. The pitch can be read off the correct blade. The blades are made pointed so that they can be inserted in small nuts to check inside threads as well as outside threads.

Small Hole Gage

The small hole gages perform the same function as telescoping gages (Figures 43 and 44), except that they are used in smaller work.

  1. Fit the ball-shaped point into the hole or slot (Figure 43).
  2. Expand the ball-shaped end by turning the screw at the end of the handle.
  3. Use micrometer to gage the measurement.

Figure 43 — Using a small hole gage.

Figure 44 — Using a telescoping gage.

Telescoping Gage

  1. Loosen the knurled nut at the end of the handle (Figure 44).
  2. Slightly tilt telescoping gage 5 to 10 degrees and lower into object to be measured.
  3. Tighten knurled nut.
  4. Remove gage by pulling across center line as indicated by arrow

Take measurement only once. Repeated attempts will produce an inaccurate reading.

  1.  Measure gage setting with an outside micrometer.

Thread Cutting Tool Gage

  1. Place the proper gage over the tool. The tool must mesh properly with no light showing between the tool and the gage.
  2. Use a 29-degree angle as a guide when grinding cutting tool.
  3. After tool fits the angle, the point should be ground off to fit the proper place on the gage for the particular number of threads per inch to be cut.

Fillet and Radius Gage

  1. A double-ended radius gage blade is used to check the inside corner or fillet of a machined part. Each blade can be locked in position by tightening the clamp.
  2. These gages can be used in any position and at any angle for both inside and outside radii.

Drill Point Gage

The method for sharpening the cutting edges of a drill is to do one lip at a time. Each lip must have the same length and have the same angle in relation to the axis of the drill.

 Set the sliding head securely on the rule at the mark equal to the length of the drill. Place the drill vertically against the rule so that the drill lip contacts the 59-degree angle of the sliding head. Hold up to light; correct angle is obtained when no light is seen between gage and drill.

Wire Gage

Determine the size of both sheet stock and wire by using a correct sheet and plate or wire gage (Figure 45).

Figure 45 — Using a wire gage.

Figure 46 — Using a drill gage.

Drill Gage

The drill gage is used to determine the size of a drill (Figure 46). Insert the drill into the appropriate sized hole. A chart on the gage indicates the correct size of drill to use for a given tap size.

Marking Gages

Press the head firmly against the edge of the work to be marked. With a wrist motion, tip the gage forward until the spur touches the work. Push the gage along the edge to mark the work, keeping the head firmly against the work.

Care of Gages and Layout Tools

Observe the following guidelines when working with gages and layout tools:


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Types and Uses

Saddler’s Awl

The saddler’s sewing and stitching awl has a round wooden handle and interchangeable blades. The awl is used to punch holes in leather and as an aid during sewing. Cover the points when not in use.

Scratch Awl

The scratch awl has a fixed tapered blade and a wooden handle. It is a steel spike with its tip sharpened to a fine point. The tip of the spike is drawn across the timber, leaving a shallow groove. It can be used to mark a point by pressing the tip into the timber. The scratch awl can also scribe a line on metal. Cover the point when not in use.

Using a Scratch Awl


Awls are very sharp and must be used with extreme caution.

Follow these steps to use an awl properly:

  1. Place material to be scribed on a flat surface. Place a ruler or straight edge on guide marks. You will already have measured and marked where you want to scribe.
  2. Remove the protective cover.
  3. Hold straight edge firmly. Hold the awl like a pencil and scribe a line along the straight edge (Figure 47).
  4. Replace protective cover.

Figure 47 — Scribing a line.

Care of Awls

Observe the following guidelines when working with awls:


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1. What instrument is used for measuring distances between two points, transferring, or comparing measurements?

A. Divider
B. Level
C. Plumb bob
D. Square

2. Wing-type dividers are available in what lengths, in inches?

A. 3, 4, and 10
B. 5, 9, and 11
C. 6, 8, and 12
D. 7, 9, and 13

3. What tool is used in conjunction with a scale or rule to determining the thickness of a surface?

A. Caliper
B. Depth micrometer
C. Divider
D. Square

4. Slide calipers can be used for which of the following purposes?

A. Finding shaft centers
B. Measuring chamfered cavities
C. Measuring distances beyond the range of calipers
D. Measuring inside dimensions

5. What type of caliper measures distances beyond the range of calipers?

A. Hermaphrodite
B. Slide caliper
C. Spring-joint
D. Trammel

6. On a vernier caliper, the vernier scale is divided in to how many parts?

A. 15
B. 25
C. 32
D. 64

7. What result, if anything, occurs when calipers are dropped?

A. Causes inaccurate measurements
B. Loosens the spring for smooth operation
C. Removes excess paint for easier handling
D. Nothing; calipers can be dropped without damaging them

8. What tool measures distances to the nearest one-thousandth of an inch?

A. Caliper
B. Metric rule
C. Micrometer
D. Square

9. The Navy uses outside, inside, and what other type of micrometers?

A. Depth
B. Helical
C. Specific
D. Radius

10. What distance is the longest movement a micrometer spindle can make, in inches?

A. 1/4
B. 1/2
C. 3/4
D. 1

11. A 6-inch micrometer will measure work between which of the following thicknesses?

A. 2 to 6 inches
B. 3 to 6 inches
C. 4 to 6 inches
D. 5 to 6 inches

12. On a standard micrometer, one complete revolution of the micrometer screw will move the spindle what distance, in inches?

A. 0.015
B. 0.025
C. 0.125
D. 0.225

13. On a vernier micrometer, the ten spaces on the vernier are equivalent to what number of spaces on the thimble?

A. Five
B. Seven
C. Nine
D. Twelve

14. In reference to the care of micrometers, which of the following statements is true?

A. All micrometers should be kept in a single container to save storage space
B. Micrometers should be stored in areas where the humidity is very high to prevent rust
C. Micrometers should be coated with a light coat of oil to prevent rust
D. The graduations on micrometers should be painted so they can be easily read

15. What is the simplest, most common measuring tool?

A. Digital measuring device
B. Flat steel rule
C. Measuring tape
D. Wooden folding rule

16. What minimum distance will the folding rule section measure, in inches?

A. 4
B. 6
C. 8
D. 10

17. What measuring tape length, in feet, is the most common?

A. 25
B. 50
C. 75
D. 100

18. What measuring device is designed to take lengthy exterior measurements?

A. A 100-foot measuring tape
B. Digital measuring device
C. Laser ruler
D. Measuring wheel

19. What personal protective equipment must you always wear when using measuring tools?

A. Hard hat
B. Leather gloves
C. Steel toe boots
D. Eye protection

20. Which of the following is a rule for caring of measuring tapes?

A. Keep the case intact
B. Always oil the steel tape after each use
C. Retract the tape quickly to prevent kinks
D. Apply oil to the spring joints

21. What type of level has an extra-large vial to ensure accuracy?

A. Iron bench
B. Striding
C. Master precision
D. Machinist’s

22. On the carpenter's level, one vial is mounted vertically and another is mounted horizontally; what angle does the third vial measure, in degrees?

A. 35
B. 45
C. 55
D. 90

23. Which of the following levels is used to hang on a cord?

A. Digital
B. Line
C. Striding
D. Torpedo

4. Plumb bobs establish true vertical transfer, line-up references, and what other measurement?

A. A reading or sounding in tanks
B. The depth of a crack in a cement wall
C. The depth of a pylon hole
D. The distance between two vertical points

25. For short term storage of plumb bobs, what process should be completed?

A. Apply a heavy coat of oil
B. Apply a light coat of oil
C. Soak the plumb bob in mineral oil
D. Wrap the plumb bob with waxed paper

26. Which of the following materials can machinist’s scribers mark or score?

A. Wax, cardboard, aluminum
B. Wax, glass, cardboard
C. Steel, glass, copper
D. Steel, glass, wax

27. To protect the points of scribers, what item can be placed over them?

A. A cork
B. A piece of foam
C. A large piece of plastic
D. A small piece of hard wood

28. What is the main use for a carpenter’s square?

A. Check sections of work
B. Placing nails along a beam
C. Measuring 360-degree angles
D. Reaching areas where hammers won’t fit

29. What is a combination square used for?

A. Lay out angles for rafters
B. Measure and cut drywall
C. Measure the accuracy of a right angle
D. Measure extended exterior lengths

30. What personal protective equipment must you always wear when using a square?

A. Eye protection
B. Gloves
C. Hard hat
D. Steel toe boots

31. When using a square as a saw guide, what item should you use to hold the square?

A. A clamp
B. A wood screw
C. An assistant
D. One hand

32. By what characteristic are surface gages classified?

A. Length of the rule
B. Length of the spindle
C. The height of the gage
D. Type of surface it can measure

33. Which of the following tools can be used to measure the thickness of paint?

A. Dial depth gage
B. Machinist's level
C. Master precision level
D. Rule depth gage

34. On what axis should measurements be made with depth gages?

A. Diagonal
B. Latitudinal
C. Longitudinal
D. Rotary

35. What tool provides a true and smooth surface to make accurate measurements?

A. Surface gage
B. Surface plate
C. Vernier depth gage
D. Work bench

36. To prevent rust, you should apply a light coat of what product to all metal parts of gages?

A. Fuel
B. Grease
C. Oil
D. Silicon

37. Which of the following tools is used as a standard to determine whether or not one or more dimensions are within specified limits?

A. Calibrated vernier depth gage
B. Dial gages
C. Micrometers
D. Ring and snap gages

38. What class of gages has a commercial finish?

A. X
B. Y
C. Z

39. Before an adjustable snap gage can be used, which of the following procedures must be accomplished?

A. The gage must be cooled to below freezing
B. The gage must be heated to a predetermined temperature
C. The GO and NO GO buttons, pins, or anvils must be set to the proper dimensions
D. The locking screw and the adjusting screws must be removed

40. Before using gage blocks, you should take which of the following actions?

A. Boil the gage blocks in water
B. Freeze the gage blocks
C. Remove the adjusting screws from the gage blocks
D. Remove the coat of rust preventive compound from the gage blocks

41. When checking gages, at what location should they be placed?

A. In a vice
B. In your hands
C. On the work bench
D. Between clamps

42. The moisture from your hands contains an acid that can cause what gage block problem?

A. Attract an electrical charge
B. Become brittle
C. Stain
D. Warp

43. After cleaning gage blocks, you should always take which of the following actions?

A. Boil the gage blocks in gasoline
B. Coat the gage blocks with heavy grease
C. Cover the gage blocks with a film of acid-free oil
D. Paint the gage blocks with lead-free paint

44. What total number of thickness gages are usually grouped together in one tool?

A. 13
B. 26
C. 39
D. 52

45. Screw pitch gages are made to check metric, V-form, and what other types of threads?

A. Automotive
B. British Standard
C. Square-D
D. Whitworth

46. Telescoping gages are used for which of the following purposes?

A. To gage larger holes
B. To measure outside distances
C. To measure the depth of large holes
D. To measure the lenses on telescopes

47. On a thread cutting tool gage, what do the numbers represent?

A. The length of a screw or bolt
B. The number of threads on a screw or bolt
C. The number of threads per foot
D. The number of threads per inch

48. Which of the following tools is used to check the accuracy of drill cutting edges after grinding?

A. Drill point gage
B. Marking gage
C. Rule depth gage
D. Thickness gage

49. A wire gage is normally what shape?

A. Circular
B. Rectangular
C. Square
D. Triangular

50. What gage is used to determine the size of a drill?

A. Center
B. Drill
C. Drill point
D. Thread cutting

51. Marking gages are normally made from which of the following materials?

A. Copper or tin
B. Paper or plastic
C. Plastic or glass
D. Wood or steel

52. Which of the following tools can be used to check the piston ring gap clearance in a cylinder bore?

A. A marking gage
B. A thickness gage
C. A wire gage
D. An awl

53. What type of gage measures the inside corner of a machined part?

A. Drill point
B. Fillet and radius
C. Telescoping
D. Thickness

54. What tool is used as a gage for leveling and setup work?

A. Adjustable parallel
B. Angle plate
C. Magnetic base indicator holder
D. Marking gage

55. What tool is used on any machine where graduations are difficult to read?

A. Adjustable parallel
B. Angle plate
C. Magnetic base indicator holder
D. Marking gage

56. What action can occur when a thickness blade is removed with the knife or a cutter of a machine is lowered onto it?

A. Shaves off the blade
B. Removes rust from the blade
C. Sharpens the knife of the machine
D. Verifies the thickness of the gap

57. Which of the following is a sharpened steel spike used to mark wood?

A. An auger
B. A push drill
C. A hand drill
D. An awl

58. At what location should awls be stowed when not in use?

A. Carpenter’s pouch
B. Machinist’s apron
C. Rack
D. Shop cork board


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Answers to Exercises

1. A
2. C
3. A
4. D
5. D
6. B
7. A
8. C
9. A
10. D
11. D
12. B
13. C
14. C
15. B
16. B
17. A
18. D
19. D
20. A
21. D
22. B
23. B
24. A
25. B
26. C
27. A
28. A
29. C
30. B
31. A
32. B
33. A
34. C
35. B
36. C
37. D
38. C
39. C
40. D
41. B
42. C
43. C
44. B
45. D
46. A
47. D
48. A
49. A
50. B
51. D
52. B
53. B
54. A
55. A
56. C
57. D
58. C


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