Measuring Tool Basics: Day 1, Start Off Right - Haas Automation Tip of the Day

Hello and welcome to this Haas Tip of the Day. What I hold in my hand is the modern world, the result of thousands of years of manufacturing refinement. Okay, a bit much? Maybe. This is actually a hub for our side mount tool changer arms, but what it represents is incredible. The fact that we can measure every feature on this part with near certainty allows us to machine perfect part after part and those can be shipped all over the world where we know that they will fit into an assembly just as design. Part interchangeability and our modern assembly lines are only possible because of good machinists making and measuring good parts. Now in today's video we opened up our toolbox and we pulled out some of our most basic hand measuring tools. Okay, okay. Some of our most basic handheld measuring tools and what's needed to use them. So stick around. Everything for me begins with my setup. So check this out. I've got a block loaded up. Now if you're tightening up those tools by hand. These are the measuring tools that we're going to take a look at today and we're going to spend most of our time on calipers and micrometers. If you work in a machine shop this is what you have to master if you want to progress in the trade. So we're going to start with our trash bags. Where else would we start a video on measuring tools, right? So let's take a look at the fine print. It says here that these bags are 1.1 mil or 27,9 ums thick. Did I sound like a machinist when I read off those those numbers? Nothing I said sounded like a machinist. So can anyone tell me how thick these trash bags are in inches or in millimeters? There are still some industries here in the U.S. that refer to one thousandth of an inch .001 as a mil. You might hear that term when measuring the thickness of paint or a plating thickness or when measuring the thickness of plastic sheets or plastic bags. But as machinists we don't use the term mil. It just doesn't sound right. We use the term thou as in one one thousandth of an inch. Mil sounds too much like millimeter and it's just confusing. So we need to learn the slang of the machinist if we want to be understood. This is one inch 1.0. This is 1.1 inch or 1 inch 100 thou. This is 1.15 inches or 1 inch 150 thou. This is 1.157 which is 1 inch 157 thou. And this is 1 inch 157 thou and 5 tenths. This is basic stuff but that just makes it all the more important to get right around the shop. In the same way that the thou is the base unit for the way we talk in the inch system, the um is the base unit for the metric system. Okay it looks like um but don't call it that. Okay you'll sound really really weird like I did just now. This is actually a lowercase greek mu followed by a lowercase m and this stands for micrometer in the metric system. One millionth of a meter or one thousandth of a millimeter. Now to avoid confusion between this micrometer and this micrometer we just call one thousandth of a millimeter a micron. So 0.001 in the imperial system is one thou. 0.001 in the metric system is one micron. That means that these trash bags are 1.1 thou thick about 28 micron. That is how a machinist speaks a thou and a tenth. Now these trash bags over here three mil thick which is three thou thick or about 76 micron. Oh this might be a great spot to mention that there are exactly 25.4 millimeters per inch. So we can use those numbers to convert from millimeters to inches or inches to millimeters. Well now that we know the language of the machinist thou and microns we can move over to our yardstick. Now on this yardstick the graduations come uh oh a graduation is uh just the line uh that we measure to. On this yardstick they come every one eighth of an inch. So one divided by eight equals 0.125 inches or 125 thou. Here in the you've got to get really good at converting between fractions and decimals. So eighth of an inch quarter inch half inch three quarter inch and so on. Now for the metric meter stick the graduations come every millimeter. There are 10 millimeters in a centimeter and a thousand millimeters in a meter. Way over here on this meter stick if we look right here we could call this 58.5 centimeters or 585 millimeters either way. So this is our meter stick our yardstick and it is not the most accurate measuring tool. Now our tape measures are only slightly better but they're really useful uh as machinists when rough cutting material. Right off the bat I might think that this tape measure is broken. The end is all wobbly. Now how accurate can that be? Not so fast. It's not broken. The end hook on a tape measure is supposed to move. The hook is slotted so it can slide on its rivets forward and back by the width of the hook. It can give accurate measurements while either pushing or pulling. Genius! Now I know this is basic but it's good right? Every machinist needs to know this. Accurate measurements start with knowing your tools. Now actually over the last few years I've seen more and more ads online that actually specifically ask that operators know how to use a tape measure. It's the basics. So on an inch tape measure the graduations are now coming every 1 16th of an inch. 1 divided by 16.0625, 62 and a half thou. For metric tape measures the graduations are still coming every every millimeter. No big change there. Pretty consistent. Here we start getting into some machinist tools that are accurate enough to make some pretty decent measurements. I'll often carry around one of these in my shirt pocket. Now a lot of us got scolded at our first machinist jobs for calling this a ruler. The old guys will chime in and say a ruler is a king or a queen. This is a scale. What's funny is that these typically aren't scales anymore either. Back in the day our grandfathers would hand draw prints using architect or engineer scales to get the proportions correct when not drawing parts life size. When a drawing is the same size as the real part we call that scale one to one. If the drawing is half the size of a real part the scale would be one to two. Now here are my grandfather's old scales with different ratios. The graduations on them vary based on the scale we want to draw the part at. The machinist rulers or scales that I use today typically have a precision edge on them and they're just called steel rules. These typically come with graduations of 1 32nd and 1 64th of an inch while metric steel rules will go down to millimeter and one half millimeter graduations. So our our rulers that we've looked at have graduations all over the place eighth inch 16th 32nd and 64th graduations and this can get really confusing. We've just gotten used to it here in the states and we've gotten really good at converting fractions into decimal inch values which brings me to one of my favorite machinist quotes. Instead of our engineers and machinists thinking in eighths sixteenths and thirty seconds of an inch it is desirable that they should think and speak in tenths hundredths and thousandths. This was written by Sir Joseph Whitworth way back in 1857. In fact he coined the term thou one thousand seven inch way back in 1844. Thank you sir. So the steel rule that I tend to carry most often in my pocket is actually a decimal inch version. It'll have the 0.1 0.2 0.3 inches on the one side which match up well with our decimal inch digital micrometers that we were looking at and our Haas control which doesn't list things in 64ths it lists things in decimal inches. So no more scant or heavy 64ths. This is by far my favorite steel rule. Now if you want to look like a real pro when using a steel rule be sure to set it on its edge when measuring. You'll get much more accurate and repeatable measurements. By placing the rule on its edge we avoid parallax where the measurement appears to change on us based on the direction we view the graduations from. Each of these measuring instruments has a different accuracy a precision that a trained person can be expected trusted to hold with one of these instruments. Often but not always the accuracy or precision of an instrument is the same as the smallest graduation on that tool. So our yardstick had eighth inch graduations and these calipers here which which have to be the most versatile tool on this table have a resolution down to five tenths while these dial calipers here have a smallest graduation resolution of one thou. Now in reality I don't use calipers for for numbers that small. Once I go down below a couple thou or a thou I'll start using micrometers so that's just typically what we do why why push the limits. To be used accurately these need to be zeroed out with each use held square to the part and used with just the right amount of force not too much. We'll wipe the reference surface with a lint-free cloth and we might wipe that same surface with a drop of micrometer oil. We'll open and close the calipers to make sure nothing is dragging or catching and if the calipers drag while opening or don't fully close the calipers might have been damaged and they'll need repair. We'll wipe clean the measuring faces and close them snugly. We can hold the calipers up to a light to make sure there is no gap between the jaws. If there is clean them again or get them repaired. With the jaws closed we'll origin or zero out the calipers. I'll open and close them a few times at this point to make sure I get zero repeatably. We can zero out dial calipers by rotating the bezel and snugging the set screw. These calipers are like the Swiss army knife of machinist tools. They can be used to measure inside features, outside features, depths, or a step or a shoulder. I have five things for you to watch out for when using calipers as you gain experience. One, don't push too hard and keep the part as deep in the jaws as possible. It's a good idea to hand a new machinist a gauge block or a standard to practice with when they're getting a feel for how hard to press. If you don't get the number on the standard gauge block or pin then you are pushing too hard or too lightly. Number two, make sure that your calipers are square to the part that's being measured. If they're tilted you could end up with errors. Number three, watch out for the radiuses left by tools. These can throw off your numbers. This part has a ten thou inside corner radius which can affect my values. In this case I just rotate the calipers to allow the notch on the depth measuring face to avoid that inside radius. Number four, these calipers are great for measuring IDs, inside diameters, of holes but not small holes. When a hole is smaller than four millimeters diameter, 157 thou, these inside diameter jaws aren't going to fit cleanly and your numbers are going to be off. You'll usually show the hole being smaller than it actually is. This happens just because of the physical design of all calipers, even the good ones. So for really tiny holes you're probably better off going with a small bore gauge or gauge pins of some kind. And number five, if you're using a dial caliper make sure you're looking at the needle from straight on. If you're looking at it from the side we'll get parallax error like we saw earlier with the steel rule. Once you're getting some good measured numbers with your calipers we can try some advanced caliper tricks like coming up with the center to center distance between two holes. By zeroing out your calipers on the ID of a hole you can then easily check the center to center distance between holes of that same diameter. This makes reverse engineering some parts go really quickly. This little trick is why I prefer digital calipers over dial. That and the fact that we can change them from inch to metric quickly and they look great in a holster. For more precise measurements we're going to set our calipers down and move up in the world to micrometers, not to be confused with micrometers. Okay, now the biggest difference, one of the differences between calipers and micrometers is that calipers can work across an entire range. These are eight inch calipers, they work from zero to eight inches. Now micro micrometers have a limited range, usually one inch or 25 millimeters. Now this set of micrometers, which covers zero to six inches, requires six different micrometers. Zero to one, one to two, two to three, five to six, etc. The reason I mention this is that they are zeroed differently and micrometers, the zero needs to be checked with every use, right? And so this is something that's important. Look, the spindle on these one inch or 25 millimeter mics can close all the way against the mic anvil, all the way to zero. And as I do that, it's a good time to check to make sure that there's no drag, kind of like when we're opening and closing the calipers. As I close up these micrometers, if we feel a drag of any type, they might have been damaged and they might need repair or maybe the spindle clamp is tightened just slightly and needs to be released or at least cleaned up. You can use some micrometer oil and clean those spindles. To clean and check zero on these, we'll slowly tighten the mics, clamping against a piece of lint-free paper. Once lightly clamped, we can drag out the paper, which in turn cleans the measuring faces. And we can do this a few times. Now I've often used whatever random paper that's laying around to clean my mics, but this is a bit dangerous. If the lint from regular paper gets stuck on the faces, it'll throw off all of our measurements. So lint-free paper is the way to go. Okay, all clean, no lint, time to tighten up these micrometers and check out our zero. Now here's where we run across what might be the number one issue, cause of mistakes, when using micrometers. I'm talking about Gorilla Grip. If we over tighten these mics, our measurements can end up being off by quite a bit. In fact, if you are buying a set of micrometers, it's worth it to spend a little extra and get a force limiting device, like a ratchet stop or a slip clutch of some kind, which help give us a consistent clamp, whether measuring a part or setting our zero. And it helps us prevent Gorilla Grip. Now for our digital mics, we'll just close them and origin them out, setting them back to zero. Now if we're using larger digital mics, these big ones, we can clean the measuring surfaces and origin them while clamped on a standard or on a gauge block. Now if we're checking zero on our analog mics, we'll do the same thing. They're all closed, ready to go, and they should read zero. If they don't read zero, then we have to adjust them. And to do that, we're going to take the little wrench, the little spanner wrench that came with the micrometers, and we're going to lock it onto the sleeve and rotate it slightly until the lines line up, zero, zero. Now this doesn't have to be done often. So if you're new to machining and you think your mics aren't reading correctly, grab a buddy and have them take a look at the mics before you make any adjustments. Again, that sleeve might be hard to turn if it hasn't been adjusted in a long time. So you might have to clamp it in a mic vice. You might actually have to tap on the spanner wrench just a tiny little bit with a hammer. With our mics all zeroed out, we can measure a part. Now I'm going to grab these digital mics and this part, and I'll set it on here. We're going to jiggle things to make sure everything's nice and square. We're going to rotate our ratchet stop a few revolutions, click, click, click. And then there's our number, 595 thou and two tenths. Now to get that same measurement with an analog mic, we're going to have to read between the lines and do some addition. For inch micrometers, the main graduations etched on the sleeve are a hundred thou apart. 0.1 inch, 0.2, 0.3, 4, 5. That's 0.5 inches. We haven't quite made it to 6. We haven't graduated to 0.6. The smaller graduations on the sleeve are 25 thousandths of an inch apart. 25, 50, 75. And we aren't quite to our next line yet, so we'll call this 0.575 so far. But wait, there's more. Now we move over to our thousandths graduations, which are etched on the micrometer thimble. Our highest full line number is 20, so we just add this in. 0.595, 595 thou. Actually, we're just a little bit over that. We're kind of in between 595 and 596. So for higher precision, out to a tenth of a thou, we'll look over to these numbers, 0 to 9, etched around the circumference of the micrometer sleeve. These markings are part of what we call a Vernier scale, and there's a secret code to them. They help us read between the thou lines, the graduations, on our thimble for higher accuracy, higher precision. For this Vernier micrometer scale, all we do is look over all 10 numbers, 0 through 9, and decide which one best lines up with the thou graduations on the thimble. Now, it doesn't have to line up with any particular thou line. Any one of them will work. It just has to line up well. Our eyes can play tricks on us, so we have to be careful to avoid parallax. Yep, just like that steel rule, we need to look straight down at those numbers. So finishing up our math lesson here, we have 0.5 plus 25, 50, 75, plus 20, plus two tenths, gives us 0.5952, 595 thou and two tenths. Metric micrometers are very similar, with graduations of one millimeter and half a millimeter on the sleeve. Graduations on the thimble every 0.01 millimeters, 10 micron. And a Vernier scale on the sleeve, which lines up to an accuracy of one micron. We'll see these Vernier tenth scales on lots of different kinds of micrometers, so it's something we really need to master. So that was some pretty solid instruction on calipers and micrometers, our common tools. I'd like to quickly gloss over bore gauges, gauge pins, and blocks before we let you loose here, just so you know what people are talking about when you see them. Bore gauges are used to accurately measure hole inside diameters. Now they are similar micrometers in that they are only good for a certain range of bore. This set comes with adjustable anvils, rods, that can be swapped out or stacked, so the gauge can be used with different diameter holes. Now we'll typically zero out our bore gauges using a precision ring gauge, and we'll check this often. And like all dial gauges, we need to look straight at the needle to avoid parallax, and digital indicators can also be attached. Now for small holes, these plug gauges, also called gauge pins or go no-go pins, are just terrific. Once the correct pins are chosen, if the go pin fits and the no-go pin does not, we can quickly gauge whether a hole is in spec. Now you can order these pins in varying tolerances based on how tight the print tolerance is for your particular feature. Now similar to our plug gauge is our thread gauge or our thread plug gauge. Now we'll order these up in a go no-go based on the callout from our blueprint. This is a 516-18 thread with a fit tolerance of 2B. Now for most threads, we'll check the hole size, the thread minor diameter, with a go no-go pin. And then check the thread pitch itself with a go no-go thread gauge. This is a good thread. Some of you have noticed that I'm measuring this particular part after coating. Now you'll need to watch out for coatings. This part has a black oxide finish on it, which is a conversion coating and leaves virtually no buildup, so we don't have to mask anything on it. If this were an aluminum part getting anodized, you'd really have to plan out the entire part, deciding if you're going to mask certain holes or not, or if you needed to machine the part undersized to account for the coating that's going to build up later. Most anodized parts might have a buildup of a half a thou to maybe four thousandths of an inch, depending on the type of anodize. Well, we really dove deep into a couple of the common tools that we use every day as machinists, but we glossed over some of these other topics. But we're going to be making videos on those soon in the future, so be sure to subscribe to the Haas Automation YouTube channel or like us on Facebook. Well, that's it for this Haas Tip of the Day. Thanks for watching.