ACCURATE MEASUREMENTS by Steve Bodofsky Reading a Micrometer

n the last issue of GEARS, we Choosing the right mic is the one that fits over the looked at micrometers: What they Right Size Mic object you’re measuring, and adjusts Iare, basic terminology, and how to The first step in using a microm- tight enough to provide a measurement. use them. In this issue, we’ll discuss eter is choosing the right size mic. If the thimble rotates past the sleeve how to read the scale on a micrometer, Micrometers come in various sizes, but measurements, and the part you’re mea- or mic. While there are many differ- are only designed to measure within a suring doesn’t fit snuggly between the ent types of mics, the scales are pretty range of about one inch. For example, anvil and spindle, you’re using the much the same. the set shown in figure 1 includes three wrong mic. As with the caliper, micrometers micrometers: are available in a digital format, and • Zero to 1 inch Reading the Scale can be had for a fairly reasonable price • 1 to 2 inches Imperial (Inches) if you’re willing to shop around. For • 2 to 3 inches Now we’re ready to look at the that matter, a digital caliper will prob- scale. This is the part of using a mic ably provide you with adequate accu- The thing to remember is that the that’s fairly consistent, regardless of racy and resolution for most of your first digit in your measurement will what type of mic you’re using. measurement needs. always be the smaller of the two mea- Start by looking at the sleeve (fig- But assuming you’re willing to surements in the range. That is, if ure 2): It has a number of different-size spend the time necessary, and want to you’re using a zero-to-one inch mic, the graduations. The largest graduations are be sure of the most accurate measure- first digit will always be a zero: numbered, from zero to 9. Those each ment possible, a micrometer may be 0.xxxx" indicate a tenth of an inch, or 0.1000”. the tool for you. Let’s look at how to If you’re using a 1-to-2 inch mic, Each of those graduations is divided read them, starting with a micrometer your first digit will always be a 1: into four equal parts. So those smaller that’s calibrated for Imperial (inches) 1.xxxx" graduations are each equal to 0.0250”, measurement. How do you choose the right size because 4 x 0.0250” = 0.1000”. mic? That’ll be pain- Now look at the thimble (figure fully obvious the first 3). Each full rotation of the thimble is time you try it: The equal to one of the small graduations

Figure 1: Micrometers come in a wide range of sizes, with a limited range of measurement. In virtually every case, the Figure 2: Each of the numbered graduations on the sleeve is first digit of your measurement will be the lower range of equal to a tenth of an inch. Those are divided into four smaller the mic. graduations, each equal to 0.0250”.

52 GEARS October 2007 Parts for Automatic Transmissions SEE YOU IN LAS VEGAS! Please call for an appointment with us: Phones: +49 171 3307071 or +49 151 12116705 [email protected] www.newco-autoline.de Reading a Micrometer on the sleeve, or 0.0250”. The thimble is divided into dif- ferent sized graduations, too. The longest graduations are numbered by fives; each of them is equal to 0.0050”. Those graduations are divided again; how many times depends on the resolution of your micrometer. In this case, the larger graduations are each equal to 0.0010”; the small- er equal 0.0005”, or five ten-thousandths of an inch. That’s pretty good, but it’s not the limit of our resolu- tion. Take another look at the sleeve. See those extra divi- sions, running perpendicular to the first set we discussed (figure 4)? That’s called the vernier scale; each graduation on the vernier scale is equal to 0.0001”. So this micrometer can provide measurements that resolve down to one ten- Figure 3: A full rotation of the thimble equals one graduation thousandth of an inch! The trick to reading the micrometer on the sleeve. And the thimble is divided into smaller gradua- is to add the readings on each scale, to provide a single, tions; in this case, down to 0.0005”. complete measurement of the object. TIP: Not all micrometers have a vernier scale; in fact, not all mics have a scale that reads down below 0.001” (figure 5). In that case, all you can do is estimate the ten- thousandths measurement, based on the position of the thimble in relation to the spindle. Measuring with a Mic Imperial (Inches) Now let’s see how to read the micrometer scales to measure an object. For this measurement, I’ve chosen a small adjustable wrench. To make the measurement (figure 6): • Zero the micrometer. Figure 4: The vernier scale allows you to refine your measure- • Open the micrometer enough to allow the item to ment even further; down to just 0.0001”. fit between the anvil and spindle. • Close the micrometer against the area you want to measure, using the ratchet to adjust it against the object without overtightening it. • Lock the micrometer spindle using the locknut. If you’re unsure of any of these procedures, read the Accurate Measurements article in the last issue of GEARS. Now we’re ready to read the measurement. To make it easier to read and explain, I’ve decided to cheat just a bit: I’m using a flattened drawing of the micrometer scale, adjusted exactly the way the micrometer displayed its Figure 5: Not all mics have a vernier scale. If yours doesn’t, measurement (figure 7). This just makes it easier for you you can estimate the difference between the zero line and the to read the display all at once, without having to rotate the graduations on the thimble. micrometer to see all the different scales. Think of it like �

� � � � � � � � �

� � � � � � � � � �

Figure 6: The procedure for measuring an object with Figure 7: This is a flattened version of a micrometer scale; like an outside mic is always pretty much the same. If you’re using a world map instead of a globe. The advantage is it lets unsure of the procedures, read the Accurate Measurement you examine all of the scales at once, without having to rotate column in the last issue of GEARS. the mic to see the rest of the scale — a big benefit in print! 54 GEARS October 2007 )NSIDEEVERY4RANS4ECšKITYOULLALWAYSlNDTHEHIGHESTQUALITYCOMPONENTS THE MOSTCOMPLETETECHNICALINFORMATIONANDLOGICALSUB PACKAGING.OBODYMAKES TRANSMISSIONPARTSMOREDEPENDABLE"ETTERPARTSANDBETTERPERFORMANCE MEANSLESSCHANCEOFACOMEBACK SOINSISTONREBUILDINGWITHTHEBEST )NSISTON4RANS4ECšKITSFROM&REUDENBERG ./+ THE/%SUPPLIERWITH AFTERMARKETVISION

4s&sWWW4RANS4ECCOMs-ILAN /( 


)F)T#OMES"ACKADREVINDD 0- Reading a Micrometer using a map of the world instead of a globe; everything’s � right there in front of you, instead of rotating it to see what’s on the back. Since the micrometer we used was a zero-to-1 inch mic, the first digit will be a zero: 0.xxxx” � � � Next we look at the large, numbered graduations on � the sleeve. The thimble is back far enough to reveal the � third numbered graduation, so the measurement is at least � three tenths of an inch. Here’s what we have so far: � � � 0.3xxx” � � � � � � � � � � A closer look at the sleeve reveals at least one smaller graduation is showing; maybe two. So which is it, one or two? It’s one; here’s how we know: Look at the graduations on the thimble (figure 8). Figure 8: Are we seeing one graduation or two past the 3 on Notice we’re close to the 20; that is, we’re near the end of the sleeve? It has to be one, because we’re too close to the its scale. Remember, each rotation of the thimble is equal to high end of the scale on the thimble. one small graduation on the sleeve. So, since we’re near the end of the scale on the thimble, we’re just short of the sec- � ond graduation on the sleeve. That’s why we can see a little of the next graduation, even though we haven’t reached the second graduation yet. Okay, so we have one small graduation showing on the sleeve; that’s another 0.0250”: � � 0.3000” � + 0.0250” � 0.3250” � � � Next, look at the graduations on the thimble (figure 9). � � The zero indicator line on the sleeve is lined up just a bit shy of 21. 21 would be 0.0210”; since this is less, it’d be � � � � � � � � � � 0.0200”. But there’s another, short graduation, between the 20 and 21. That’s 0.0005”, so the thimble reads 0.0205”. That’s how much we add to the formula: 0.3000” Figure 9: The graduations on the thimble tell you how much 0.0250” to add to your initial measurement. In this case, you’ll be + 0.0205” adding 0.0205”. 0.3455” � But wait; there’s more! Notice that the zero indicator is just a tiny bit past the 0.0005” mark. This is where the ver- nier scale comes in. Look at the vernier scale, and find the graduation that lines up with a graduation on the thimble (figure 10). In this case, it’s the 3. That’s another 0.0003” � � to add to the total. So our final measurement is: � � 0.3000” � 0.0250” � 0.0205” � + 0.0003” � � 0.3458” � � � � � � � � � � And that’s the final measurement in inches: 0.3458”. Reading a Metric Mic Some of you aren’t forced to fight with measuring Figure 10: To refine your measurement even further, see which length in inches, feet, yards and miles. Some of you get to graduation on the vernier scale lines up with a graduation on the work in simple decimal equivalents, known as the Metric thimble. Then add that number to the 1/10,000ths column.

56 GEARS October 2007 New SuperFlow TransDyno SF-66K The convenience, reliability, versatility and ability to test virtually every transmission on the road, including the new Allison models. Handles hydraulically and electrically shifted transmissions, foreign and domestic, in FWD, RWD and AWD confi gurations. Monitors and tests virtually every aspect of transmission performance, under simulated road load conditions, before the transmission is installed … supported by the accuracy and superior documentation of the exclusive TDAC (Transmission Data Acquisition & Control) System.

Shown with manual console. SuperShifter The NEW Durable In-Car Tester Rugged design, solid Valve Body Testers state electronics, Precision test valve bodies, impact-resistant housing. Solenoid Testers solenoids and pressure Tests most late model transmissions. Controls A must for testing the transducers with actual the transmission from inside the car. Tests Solenoid weakest link … six at transmission pressures and current/resistance. Operator ID and Date/Time stamp. a time. Easy to use. heated oil under toughest Embedded Bluetooth for external device connectivity. simulated driving conditions.

TCRS Torque Converter Test and Rebuild Systems Excellent profi t center for transmission repair shops or stand-alone startups … and smartest way to save time and prevent costly comebacks.

New! Improved! Single Gun Auto Weld Aligner Torque Converter Standard of the industry. Balancer And choice of the big three now with automatic — Ford, GM, Daimler-Chrysler. weight indexing, Check out converters Air-operated collets. Patented runout compensa- BEFORE you ship or auto-tack and auto-weld. tion mode, push install with HUB RUNOUT Do “bowl buildups” and buttom polishing INSPECTION UNITS. And, weld on impeller hubs. and better accuracy ensure your converter TAC 12+ control panel lets and repeatability quality (after welding) you automatically control than ever before. with AIR TEST STANDS number of tacs and duration. for diagnosing leaks.

Hicklin Heavy-Duty Transmission Dynamometers for trucks, mass transit, military, off-high- way. In-line v-drive … angle drive … Allison, Renk, ZF, Voith and many others. Also ask about towing, axle and brake dynamometers for medium- to heavy-duty trucks; and torque converter dynamometers for testing under real-world, full-load conditions.

When you SuperFlow Dynos and Flowbenches Recognized world leader in fl owbench technology, plus a really need wide range of engine dynos, chassis dynos and software. Helps OEMs, high performance test engineers and engine to know… builders take performance to the next level.

www.superfl ow.com 4060 Dixon Street • Des Moines IA 50313 • ph: 888-442-5546 or 515-254-1654 • fax: 515-254-1656

ssuperflowuperflow ad.inddad.indd 3131 112/26/062/26/06 11:38:4811:38:48 AMAM 8354 Gears_TestCenterAd_Dec2006.1 1 12/13/06 4:27:02 PM Reading a Micrometer system. For you, there are specially designed micrometers, calibrated in millimeters. One of the first things you might notice about this Metric micrometer is that it doesn’t have a vernier scale (figure 11). It only measures down to hundredths of a milli- meter. Why aren’t Metric micrometers calibrated to resolve as well as an Imperial micrometer? Actually, there isn’t much difference between the two. Remember, millimeters are a lot smaller than inches: It takes 25.4 of them to equal just one inch. A hundredth of a millimeter equals just under 0.0004”. So the Metric micrometer provides almost the same resolution as the Figure 11: I couldn’t find a single Metric micrometer with a Imperial one, even without a vernier scale. And you can vernier scale. The reason is probably because the Metric mic still approximate more precisely, simply by paying atten- resolves low enough without needing it. tion to how close the graduations are to the zero line. NOTE: While there may be some Metric mics with a vernier scale, I couldn’t find one. I presume it’s because of the inherent resolution in the Metric mics, eliminating the need for it. If anyone has a Metric mic with a vernier scale, I’d be happy to use it to add a section to the upcoming booklet for the ATRA web site. The next thing to notice is the scale on the sleeve (figure 12). There are two sets of graduations: one above the zero line and a second below it. The set above the line is the measurement in millimeters: Each graduation equals one millimeter. The set below the line is calibrated in half- Figure 12: There are two sets of graduations on the sleeve of millimeters, or 0.5 mm. the Metric mic: The one above the zero line is in millimeters. And the scale on the thimble is divided into 50 gradua- The one below is half-millimeters. tions. Each rotation moves the thimble a half millimeter, so each graduation on the thimble equals 0.01 mm. Let’s use the Metric micrometer to measure the same wrench, and see how close the two measurements are. We’ll use the same technique to measure the wrench as before, and then read the scale. The sleeve shows 8 graduations above the zero line, so it’s more than 8 mm, but less than 9 mm (figure 13). And there’s one additional graduation showing below the line, so that’s another half millimeter. So far, the wrench is at least 8.5 mm. Now look at the thimble. The zero lines up almost exactly with the 28th graduation (figure 14); that’s 0.28 Figure 13: The thimble lines up just past the graduation on the mm. So we add the two measurements: sleeve that’s halfway between 8 and 9 millimeters. That puts 8.50 mm the measurement at 8.5 mm… so far. + 0.28 mm 8.78 mm

So the wrench is 8.78 mm thick, according to the Metric micrometer. How does that compare with the mea- surement in inches? 8.78 ÷ 25.4 = 0.3457” — just 0.0001” difference in the measurements… and that difference could have been cause by position of the mic, pressure, tempera- ture… any number of things that are beyond our control. That’s all there is to using a micrometer. There are no real tricks… nothing special to memorize. It’s mostly about taking the time to measure carefully, and to add the measurements together. Figure 14: The zero line on the sleeve lines up with the 28th Or you can get a digital, and leave the math to some- graduation on the thimble. That means you have to add 0.28 one else! mm to the earlier measurement. So the wrench is 8.78 mm thick. 58 GEARS October 2007 Together, we can move in a new direction. Park, Reverse, Neutral, Drive. Seal Aftermarket Products allows you to shift into gear with OE technology from Parker’s Seal Group; our strength is backed by 60 years of manufacturing experience dealing with customers demanding the best in sealing technology. The Seal Group consistently adds manufacturing capabilities through strategic acquisitions including Acadia Rubber, Wynns Precision and Goshen Rubber, just to name a few.

Seal Aftermarket Products utilizes Parker Seal Group manufacturing capabilities with market leading technology in developing aftermarket solutions. Seal Aftermarket Products offers kits and bulk components in over 20 different product categories; Our manufacturing capabilities include many of the best-known and most reliable products in the industry such as molded pistons, standard and custom o-ring seals, lip seals, lathe cut seals, Tefl on™ seals, and metal clad seals. Benefi t from the total Parker solution and get ready to move.

www.parker.com 1 800 582 2760 15750 NW 59th Avenue Miami Lakes, FL 33014

GEARS.indd 1 9/17/2007 4:14:06 PM