TOOLING INVENTORY

2.1 Types of Measurement

a. Discuss the use of metrology in manufacturing

It’s the technology behind the quality assurance processes in manufacturing that ensure your car runs the way it should, your computer’s processor works properly and many more aspects of daily life that most of us take for granted until something goes wrong. In manufacturing, hundreds or thousands of parts are produced each week. Most of these are produced by machines that are programmed by workers. And in modern manufacturing, every one of these parts must be produced to precise specifications to ensure a quality finished product. Over time, the machinery that produces these individual parts can shift slightly, become dull, or lose alignment in a way that causes problematic differences. That’s where metrology comes in. A Quality Control Inspector, a metrologist, or a machine operator with metrology experience can take the parts that have been produced and ensure they meet the specifications required for the finished product. If the measurements are off, the machines can then be adjusted to bring the parts back into spec. This process is ongoing in advanced manufacturing. As quality demands have continued to increase, one of the challenges has been that the human eye is incapable of measuring with the precision necessary to produce the highest quality parts needed. In industries where precision is important, like automotive, aerospace, technology and more, metrology technology like Coordinate Measuring Machines have been adopted to make measurements to within a millionth of an inch.

b. Discuss the imperial and metric conversion

Imperial units of measurement are the units that were in common usage in this country up until about thirty years ago. Even after the introduction of the metric system, Imperial units have continued to be in everyday use in varying degrees.

Metric units of measurement are the units originally used in mainland Europe, adopted in this country when we joined the European Economic Community (as it was then called) in the early 1970s. It is based upon a decimal system where each unit is divided into blocks of 10 smaller units.

Area

Mass/Weight

Volume/Capacity

c. Discuss the semi-precision and precision measurement

Semi-precision measurement

A term that usually refers to measurement when tolerances or levels of desired accuracy are within 1/64 or 1/100 inch, 0.5 millimeter or  1 degree.  

Precision measurement

Notes

d. Discuss the following: accuracy, precision, reliability, and discrimination

Accuracy: The degree to which a measurement represents the true value of something. 

Precision: The degree of resemblance among study results, were the study to be repeated under similar circumstances. Lack of precision is referred to as ‘random error’.

Reliability: A measure of how dependably an observation is exactly the same when repeated. It refers to the measuring procedure rather than to the attribute being measured. 

Discrimination

2.2 Select Proper Measurement Tools 

Identify basic semi-precision measuring tools

Ruler: A flat piece of steel with graduations that divide inches or millimeters into fractional parts; one of the most commonly used semi-precision measurement tools.

Identify precision measuring tools

Calipers

Simple calipers

Spring joint calipers

Transfer calipers

Hermaphrodite calipers

Slide calipers

Vernier calipers

Micrometers

Outside micrometers

Inside micrometers

Depth micrometers

c. Justify the use of a particular measuring tool based on tool characteristics

Calipers

Calipers are used to measure point-to-point distances, such as diameters. A diameter is the straight distance across a round object. We also use calipers to compare sizes with standards such as a graduated rule. The vernier caliper is only one of many types of calipers. 

Types of Calipers

A tank turret repairer may measure many shapes and sizes. There are several types of calipers to do this job. The repairer's job is easier if the right design of caliper is used. Outside calipers make outside measurements; inside calipers measure inside sizes. 

Micrometers 

Micrometers can make measurements that must be very precise. They are more reliable and more exact than calipers. Standard micrometers can measure distance to the nearest one-thousandth of an inch. Some micrometers have a vernier scale. These micrometers can measure distance to the nearest tenthousandth of an inch. The measurement is usually written as a decimal.

Types of Micrometers

Three types of micrometers are commonly used: the outside micrometer, the inside micrometer, and the depth micrometer.

Identify error possibilities in measurement tool selection

Ruler

A precision steel ruler, however, may be accurate to 0.001 in., depending on the length of the rule. Longer rulers have larger tolerances. With demand for increasingly tight tolerances, precision sheet metal shops may want to consider calibrated steel rulers. Calibrated with blocks and gauges traceable to a metrology lab (including the national lab at the National Institute of Standards and Technology), precision rulers and tape measures can add a degree of confidence when measuring. These devices come with a certificate showing they have been calibrated, along with data showing how far off each inch mark is to the measurement standard.

Micrometers

The most accurate hand-held tool available for skilled operators, micrometers come in various types, including digital, vernier, inside, bench, and specialized models. For most measurements, you hold the micrometer. The work is placed against the anvil with the left hand while the spindle is turned down to the work with the thumb and index finger of the right hand.. For most measurements, you hold the micrometer. The work is placed against the anvil with the left hand while the spindle is turned down to the work with the thumb and index finger of the right hand. You can adjust micrometers with two steps. First, to eliminate play in the spindle, back off the thimble, insert a spanner wrench (likely furnished with the micrometer) into the adjusting nut, and tighten just enough to eliminate play. Next, to adjust to a zero reading, clean all dirt or grit from the measuring faces by gently closing the spindle to the anvil with a clean piece of paper between them. Pull the paper out with pressure applied, then close the faces and insert the spanner wrench in the small slot of the sleeve. Next, turn the sleeve until its zero line coincides with the zero line on the thimble.

Calipers

While not having the same degree of precision as a micrometer, slide calipers offer more measurement range than a single micrometer. Slide calipers include electronic, mechanical, dial, vernier, and plain versions. The best digital and dial slide calipers, regardless of resolution, are accurate to within 0.001 in. every 6 in. The best vernier calipers are accurate to 0.0005 in. per foot. Slide calipers have two knurled thumb pieces on the slide, which make it easy to open or close the jaws, and a knurled clamping screw with a left-hand thread for locking the slide at any desired setting. The thumb on the same hand that holds the tool can be used for both of these adjustments. The slide also has a stop, preventing it from being entirely withdrawn from the body. Because slide caliper measuring surfaces are not in line with the beam of the caliper, some care should be taken not to use too much measuring pressure. This will lessen the possibility of springing the jaws. A general rule is to use good judgment for setting a minimum measuring pressure, often in the half-pound range. To check or set the separate ID nibs on a caliper, you can use a micrometer or ring gauge. Individual"feel" is important when measuring an ID because the measuring surfaces are so thin that small pressure changes can affect the reading by as much as 0.001 in. Also, be sure to keep the sliding surfaces clean and lightly oiled.

Micrometer Depth Gauges

A micrometer depth gauge measures the depth of holes, slots, recesses, and other geometries and is available in electronic, mechanical-digital, and standard readouts. The tool consists of a hardened, ground, and lapped base combined with a micrometer head. Measuring rods are inserted through a hole in the micrometer screw and brought to a positive seat by a knurled nut.

The reading is taken exactly the same as with an outside micrometer except that sleeve graduations run in the opposite direction. To obtain a reading using a rod other than the 0- to 1-in. rod, it is necessary to consider the additional rod length. For example, if the 1- to 2-in. rod is being used, 1 in. must be added to the reading on the sleeve and thimble. Before using the micrometer depth gauge, be sure that the base and end of the rod and work are wiped clean and that the rod is properly seated in the micrometer head. Hold the base firmly against the work and turn the thimble until the rod contacts the bottom of the slot or recess. Tighten the lock nut and remove the tool from the work to read the measurement.

Demonstrate proper care of precision measuring tools

Proper use and care of precision measuring tools is very important if accuracy and reliability are to be maintained.  Here are some guidelines to follow much of which is just common sense.

1. Measuring a work piece (on a lathe) should be carried out only after the work piece has stopped moving; otherwise, there could be wear on the measuring faces and the accuracy of the tool may be compromised.

 
2. Wipe the measuring faces of a precision measuring tool and the to-be-measured surface of the work piece to prevent the measuring accuracy from being negatively affected by dirt or dust. It is not advisable to use a precision tool such as a vernier caliper, micrometer or dial indicator to measure forged roughcasts or abrasive-bearing pieces, i.e. carborundum, because the measuring faces will be abraded and accuracy will diminish.

3. Never put precision measuring tools together with hand tools, such as cutting tools, files, hammers and drills for the fear of bumping and damaging the precision measuring tools. Never leave them on a lathe or other running machinery for fear of vibration causing them to fall to the floor.

4. Precision measuring tools should not be used as substitutes for other tools. Don’t use a caliper as a pry bar or screwdriver!  Don’t use a micrometer for a hammer or C clamp!  You might be tempted but don’t do it!

5. Temperature has a substantial impact on the measuring results. Different materials expand and contract at various rates. Precise measurement of work pieces should ideally be carried out with the temperature being about 70ºF but since it’s not always possible to be in an ideal situation one can minimize any error by having the work piece and the measuring tool share the same temperature some time prior to the measurement. Precision measuring tools should not be put under direct sunshine or any other heat source because accurate measurements will not be achieved as the temperature increases.

6. Precision measuring tools should never be put near any magnetic material such as a magnetic worktable, to avoid being magnetized.

7. Tools should be cleaned after use.  Perspiration in your hands can be a bit caustic and react slowly with metallic materials so it is a good practice to lightly oil the tools to minimize any chemical reaction that might take place.  Store tools in a dry place.  Never leave them outdoors.

Identify drilling, grinding and tapping

Drilling: is an economical way of removing large amounts of metal to create semi-precision round hole or cavity. Drilling allows a person to make holes through boards, metals, and other materials. Used for last removal of stock on preparation for other operations like boring, reaming, or tapping.

Grinding: is an operation in which the cutting is done by the use of abrasive particles. Grinding processes remove very small chips in very large numbers by cutting the action of many small individual abrasive grains. The abrasive grains are formed into a grinding wheel. Very smooth surfaces can be accomplished by the use of the proper grinding wheel.

Tapping: is the process of cutting a thread inside a hole so that a cap screw or bolt can be threaded into the hole. Also, it is used to make threads on nuts. Tapping is done with a tool called a "Tap". Tapping may be done by:

- hand

- lathe machine

- milling machine

- tapping machine

2.3 Apply Proper Measuring Techniques

 Calibration requirements of various precision instruments

What is calibration?

Calibration is a comparison between a known measurement (the standard) and the measurement using your instrument. Typically, the accuracy of the standard should be ten times the accuracy of the measuring device being tested. However, accuracy ratio of 3:1 is acceptable by most standards organizations. Calibration of your measuring instruments has two objectives. It checks the accuracy of the instrument and it determines the traceability of the measurement. In practice, calibration also includes repair of the device if it is out of calibration. A report is provided by the calibration expert, which shows the error in measurements with the measuring device before and after the calibration. To explain how calibration is performed we can use an external micrometer as an example. Here, accuracy of the scale is the main parameter for calibration. In addition, these instruments are also calibrated for zero error in the fully closed position and flatness and parallelism of the measuring surfaces. For the calibration of the scale, a calibrated slip gauge is used. A calibrated optical flat is used to check the flatness and parallelism.

Why calibration is important?

The accuracy of all measuring devices degrade over time. This is typically caused by normal wear and tear. However, changes in accuracy can also be caused by electric or mechanical shock or a hazardous manufacturing environment (e.x., oils, metal chips etc.). Depending on the type of the instrument and the environment in which it is being used, it may degrade very quickly or over a long period of time. The bottom line is that, calibration improves the accuracy of the measuring device. Accurate measuring devices improve product quality.

When should you calibrate your measuring device?

A measuring device should be calibrated:

According to recommendation of the manufacturer.

After any mechanical or electrical shock.

Periodically (annually, quarterly, monthly)

Hidden costs and risks associated with the un-calibrated measuring device could be much higher than the cost of calibration. Therefore, it is recommended that the measuring instruments are calibrated regularly by a reputable company to ensure that errors associated with the measurements are in the acceptable range.

2.4 Levelling, balancing and alignment

Interpret the checklist and understand the job requirements.

Levelling/alignment/balancing of measurement equipment.

Study equipment alignment techniques and procedures.

Geometry of Alignment

• Parallel,

Side to Side

•

Elevation,

–

Up & Down

•

Axial

–

Face to Face Angle

Handling tools on Allen keys in metrics and imperial.

A hex key, Allen key or Allen wrench is a tool used to drive bolts and screws with hexagonal sockets in their heads. The Allen name is a registered trademark, originated by the Allen Manufacturing Company of Hartford, Connecticut circa 1910, and currently owned by Apex Tool Group, LLC. Its genericised use is discouraged by this company. The standard generic name used in catalogues and published books and journals is "hex key".

Hex key standard sizes

Hex keys are measured across-flats (AF), which is the distance between two opposite (parallel) flat sides of the key. Standard metric sizes are defined in ISO 2936:2001 "Assembly tools for screws and nuts—Hexagon socket screw keys", also known as DIN 911, and, measured in millimeters (mm) are:

0.7, 0.9, 1.0, 1.25, 1.3, 1.5

2 to 6 in 0.5 mm increments

M2 to M6 in 0.5 mm increments (see below for M1, M2 style designation)

7 to 22 in 1 mm increments

24, 25, 27, 30, 32, 36, 42 and 46 mm

Metric hex wrench sizes are sometimes referred to using the designation "M" followed by the size in millimeters of the tool or socket, e.g. "M6", although this may be confused with the standard use of "M6" which refers to the size of a metric screw or bolt. American sizes are defined in ANSI/ASME standard B18.3-1998 "Socket Cap, Shoulder, and Set Screws (Inch Series)". Values given here are taken from Machinery's Handbook.

Using a hex wrench on a socket that is too large may result in damage to the fastener or the tool. An example would be using a 5 mm tool in a 5.5 mm socket. Because hex-style hardware and tools are available in both metric and Imperial and customary sizes (the latter sometimes labelled "SAE"), it is also possible to select a tool that is too small for the fastener by using an Imperial/customary tool on a metric fastener, or the converse. There are some exceptions to that. For example, 4 mm keys are almost exactly the same size as 5/32", and 8 mm keys are almost exactly the same size as 5/16", which makes 4 mm and 8 mm preferred numbers for consumer products such as self-assembly particle-board furniture, because end users can successfully use an imperial key on a metric fastener, or vice versa, without stripping. 19 mm keys are so close to the same size as ¾" that they are completely interchangeable in practical use.

Variants

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