How to Read Micrometers

hi everyone today we're going to be talking about how to read micrometers and we're going to be covering both inch micrometers and metric micrometers micrometer is the read in inches have a one inch range so this one goes from zero to one inch micrometers that read in metric go from zero to 25 millimetres these read down to the ten thousandth of an inch metric micrometers read down to the hundredth of a millimeter they also make larger micrometers this is a one to two inch micrometer it still only has a one inch range it has the exact same head it's just that the frame is different and measures from one to two inches and this is actually a five to six inch micrometer they go a lot bigger than that you can get a micrometer and pretty much any size imaginable the larger ones tend to cover a large range so they have interchangeable anvils that you would use to measure anywhere from say 20 to 25 inches that's because the micrometer is and those ranges end up being quite large and they don't make a whole lot of them so they're very expensive so the manufacturers basically give you a more bang for your buck with the interchangeable anvil system inch micrometers have different scales on them that allow you to read down to one ten thousandth of an inch the first one is on the stationery portion which is called the barrel I call that one the main scale the second one is on the rotating portion of the micrometer right here this is called the thimble and the third one is called the vernier scale and it's also on the stationery portion on the barrel and this is what allows us to get down to one ten thousandth of an inch so on the main scale each of these graduations is 25 thousandths of an inch so we have 25 50 75 100 and then 125 150 175 200 each of the numbered ones is one hundred thousandths of an inch the portion of the micrometer that points to the main scale is actually the edge of the thimble the edge of the rotating part so in this case you can see the edge is just past the five hundred thousandths mark so the main scale is reading five hundred thousandths of an inch or half an inch now the thimble has 25 graduations on it because each revolution of the thimble advances hit by one mark on the main scale so 25 thousandths of an inch each of these marks is one thousandth of an inch the portion of the micrometer that points to what you're reading is is this long horizontal line on the main scale and that's called the reading line now in this case and this is quite common the reading line is in between two numbers so when that happens you always take the lower of the two numbers 100% of the time no exceptions so in this case we have five hundred thousandths on the main scale and another nine thousandths on the thimble so you add those two together five hundred plus nine is five hundred nine thousandths from there we go to the vernier scale this one up here the way the vernier scale works is because there are 11 of these marks on the vernier scale in the same place as 10 on the thimble so unless you are right on the money the zero over here and the there would line up perfectly with numbers but otherwise only one of these would line up with a line on the thimble so when you're between two lines like we are here only one of these Fournier lines is going to meet up with a line on the thimble so you need to find which line that is and in this case you can see it right here the five ten thousandth line lines up with the 17 over here and you can tell that that's the one that's lined up because the 6/10 line is off a little bit one way and the four tenths line is off a little bit the other way so only one of them will line up perfectly and in this case it's five tenths so what you do is you just tack that on to the end of what you got before so we had five hundred thousandths on the main scale another nine there so we have five hundred nine thousandths and five tenths five hundred nine and 1/2 thousandth basically now if you're new to reading micrometers you may find it more comfortable to write the numbers down so again the main scale shows five hundred thousandths we have an additional nine thousandths on the thimble and that is point zero zero nine inches so you add those two together 0.5 zero nine and then again you find what's on the the vernier scale if I can get it to focus and that's five ten thousandths of an inch we're paying attention to the numbers on the vernier scale and not to the ones on the thimble that's one of the common mistakes that people make they look at this number and try to add it to what they've already got but you're looking at the numbers on the vernier scale itself so in this case it's half a thousandth five ten thousandths of an inch and you just tech that number onto the end so 0.5 0 9 5 let's talk about some of the ways that people make mistakes early on if you were to go ahead and just mark all of the numbers so point five zero zero point zero zero nine and I used to tell my students to write all of them down like this one thing that people constantly did was leave off one of the zeros in the tenths which is why I now just advocate finding that number and tacking it on to the end of what you get between these two it just seems to be a little more simple because if you do leave off one of those numbers that is a big difference your an order of magnitude off and of course then you would end up with five hundred fourteen thousandths and that is not your reading at all so if you add it that way everything comes out well but I find that people have a tendency to forget a zero in the tenth spot so let's try a couple of other examples I've moved this to a random spot and we can see the main scale shows two hundred fifty thousands of an inch and the reading line is pointing in between 21 and 22 on this micrometer so we have 250 plus another 21 again you'll always take the lower of the two numbers when you're between the line yep that's what we've got so between those we have 0.271 and then we have to find the vernier and which one actually lines up with it so we look we look and right there we see 7/10 lines up and you can see that the eight tenths line is off one direction and the six tenths line is off the other direction so seven is the only one that lines up now this is a good example of how you can get messed up by looking at the numbers on the thimble instead of the numbers on the vernier if you were to look over here you would say that it was 271 and 6/10 you're totally ignoring these numbers on the thimble these are just pointing to which of the vernier lines is the correct one and in this case it's 7/10 so we have our 271 and we just tack that 7 on to the end and that is our correct dimension 271 thousandths and 7/10 well do another random one here so let's see what we have we're just past the hundred thousandths mark so you can also see that the line on the thimble does not quite line up with the reading line so I don't think we're right on 21 thousandths there so we've got one hundred thousandths and since we're in between 20 and 21 we always take the 20 so that's easy math 120 now we find where it is and you can see since we're so close to the 21 you can kind of guesstimate and say that that is 9/10 so we're going to go right up to 9 and if we can get it to focus yeah you can see that 9 lines up the 0 is off one way and the 8 another so 9/10 is what we want we're gonna look at one more example and this is to show a really common mistake that people make especially when they're new to reading micrometers and that is saying oh well that's three hundred seventy five thousandth on the main scale three eighths of an inch now the problem with that is that until this zero on the thimble is actually even with the reading line on the main scale you're not actually to that three hundred seventy five thousand smark so what some people will do is they'll say okay that's three seventy-five on the main scale plus another 24 on the thimble so it's three hundred ninety nine thousandths and however many tenths we have here well you can tell right away that that is not actually the case because if you were at 399 you would be seeing the four hundred thousands mark so you've got to make sure that you read the correct amount of marks and pay attention to it in relation to where zero is on the thimble if zero hasn't passed the reading line then you're not actually to that next mark so in this case we really have three hundred fifty thousand plus twenty four which is three hundred seventy four thousandths which actually jives with what we see visually here were almost of the 375 mark and at that point again we would find the mark on the vernier scale which is going to be up there and it looks like the eight tenths mark three seventy four and eight tenths I should also point out that there are micrometers out there that do not have a vernier scale so this is a tubing micrometer to use for measuring the wall thickness of tubes and you can see it does not have a vernier scale so this micrometer only reads down to the thousandths however you can go ahead and estimate how many tenths there would be if you end up between a line so here I've got 200 on the main scale my reading line is in between 16 and 17 and it's about halfway through maybe a little bit more so I would guess that that is around 6/10 reading metric micrometer slightly different and that there's no vernier scale on the micrometer and the value of the increments has changed otherwise you still have a main scale and you still have a thimble scale so let's talk about the main scale the main scale is actually broken up into half millimeter marks so each revolution of the thimble is a half a millimeter and on top of the reading line here you still have the long horizontal reading line on top of this this is hold millimeters right there so every numbered one is every fifth millimeter and then below the reading scale you have marks in between those and those are the half millimeter marks so from zero with the edge of the thimble being the pointer again you would have zero 0.5 millimeters one millimeter 1.5 to 2.5 33.5 so on so forth each graduation on the thimble is point zero one millimeters so it's 50 graduations which means half a millimeter per revolution of the thimble so just like with an inch micrometer now it's just measuring so in this case we can see there's our five millimeter mark six and seven so we were past seven millimeters and then we have 0.3 0 meters showing because of the reading line so that means that we are at 7.30 millimeters so we have 7 millimeters 7.00 millimeters and it helps to write it out like this and then we have another point 3 0 millimeters so we have 7.30 millimeters showing on the micrometer right now now this is one of the common mistakes that people will make with metric mics they will get into the mindset of inch micrometer z' and think that everything is point something on metric mics you're almost always unless it's a very small measurement going to have a hole millimeter so it's going to be something point something something in this case seven point zero zero so now let's show a reading doing a half millimeter mark in this case we have nine whole millimeters showing up here and you can see there's quite a bit of space there you can see that half millimeter mark down there so this is actually nine point five millimeters showing on the main scale this is another really common mistake with metric mics is not paying attention to where the half millimeter marks are so in this case if we were to write this down we would put nine point five zero and then from there the reading lion is landing on the twenty two mark which is 0.2 to twenty two hundredths of a millimeter and from there it's just simple addition again so our reading is nine point seven two millimeters the really common mistake here is ignoring that half millimeter mark and then you would say that the reading is nine point two two that reading is also very close to ten millimeters so another option would be someone would say it's ten point two two either way you're off by a half a millimeter here's a pitfall of reading micrometers that both inch and metric micrometer share and that is this reading line is showing right now 49 one hundredths of a millimeter well one common mistake is that someone will see okay that's 11 and a half millimeters plus another point four nine and that's not the case what we have is eleven point four nine millimeters and again just like on the inch micrometers that jives with what you see you can see that 11 and a half millimeter mark but in order to have eleven and a half millimeters on the micrometer that zero right there would have to be even with the reading line so what we have is actually just 1/100 of a millimeter less than eleven and a half millimeters I hope this clears up some confusion about micrometers for some people out there and if you have any questions or comments please leave them down below thanks for watching and I'll see you next time

Channel: Stuart de Haro

Views: 694,615

Rating: 4.8961711 out of 5

Keywords: Machining, Machine Shop, Machinist, Milling Machine, Metal Lathe, Machine tools, measuring tools, micrometers, how to read micrometers, inch micrometers, metric micrometers

Id: j0ARvWwMZX8

Length: 16min 19sec (979 seconds)

Published: Tue Aug 22 2017