How to Read an Inch Micrometer.wmv

okay this is how to read a inch micrometer before we start talking about how to read a micrometer especially an inch micrometer we want to think in thousandths of an inch so this is three decimal places if we just always set our thought process to three decimal places we'll see that a micrometer will work pretty easily this is the way that machinists think so you're gonna think of point zero zero one is one one thousandth point zero two zeroes twenty thousands point nine would be nine hundred thousands a quarter of an inch you would say is 250 0.375 think of that as 735 so how much is a thousandth of an inch anyway of kind of some rules of thumb if you're thinking of a piece of paper that's about four of these point zero zero four or four thousands a quarter is about seventy thousand point zero seven zero the pencil normal wooden pencil is about a quarter of an inch think of that it's two hundred and fifty thousands point two five is a quarter of an inch okay so there are two scales to look at on a micrometer the barrel scale and thimble scale we'll look at the barrel scale first so so here's a barrel scale up close you'll notice that it's got some numbers across here and some tick marks now if an inch of micrometer is reading from say zero to one inch then this scale is well they're tenths of an inch but this would be a half an inch so that's point five or point five zero zero this first main graduation here the first big division from 0 to 1 this is 0.1 so that's a tenth of an inch or if we're thinking in thousandths of an inch that's a hundred the next big mark is two hundred or 0.2 so point two zero zero will say that is two hundred and that will make it easy to keep the decimal place straight down here that's a half an inch point five now if if this first mark is point one or 100 half of that would be 50 or 0.05 oh so the halfway between zero and point one is 50 or 50 thousandths half of that distance would be a quarter so if you're thinking in terms of thousands this would be a hundred twenty-five fifty and then this mark would obviously be seventy five point zero seven five the main scale if we want to read these together this point one somewhere out here this would be point four or four hundred and twenty five point four two five down here can you guess what this would be this would be point six seven five or six hundred and seventy five thousands now the other scale is the thimble scale and you'll see that it starts at zero and goes from one two three four all the way around to 20 21 22 23 24 and this would be the twenty-fifth so these are thousandths of an inch so if this says one this is one thousandth point zero zero one five would be point zero zero five 17 is 17,000 so point zero one seven now let's look at a reading on here this mark that you see there that tells us that we're at 0.3 and then 0.3 twenty five point three 50 and point three seven five so that mark represents 0.375 the reading from the thimble scale is zero so we don't add anything to the point three seventy-five and so the reading is 0.375 okay so here I've taken the micrometer and I have moved it just a little bit back so we're just a little bit less than point three seventy-five and the question is what's the reading now well we we're not reading from this mark anymore this mark is not actually showing even though you can kind of see it fact is that if this mark order show it would be a brand new mark and so the reading on the thimble scale would be a very small reading and as you can see we're reading 24 which is almost completely all the way around so this is a very high number so that means we're working off of the older mark which would be this one and that mark would read point three five zero now we can get the next decimal place by reading the thimble scale and that will this one remember is reading in thousandths of an inch so this is 20 thousands 21 22 23 this is 24,000 so that's point O 2 4 so the reading of this micrometer is the point 350 plus the point O 2 4 think of it as adding 350 and 24 you get a reading of 0.3 7/4 now on this slide we can see that we've gone past the zero mark so we're working off of a brand new number it's a brand new mark it's going to be a small number since its brand new we've we've moved from point three point three to five point three fifty point three seventy-five and to that we're going to add point zero zero one so if I asked you what is 375 plus one you'd be able to tell me it's three hundred and seventy six so that's the reading

Channel: etprof

Views: 636,102

Rating: 4.8861756 out of 5

Keywords: Micrometer, Inch, Measurement

Id: oiAutI0i5YE

Length: 6min 58sec (418 seconds)

Published: Fri Jan 28 2011