Measuring a Straightedge with a Precision level

[Music] let's have a little fun over here so you know we we talked about the autocollimator and how it it measures straightness right and the way it measures straightness is it it sits here and optically looks down the length of something and we move a reflector along the length of this and then it it records tilts okay which are which are really changes in elevation in a surface okay so there's other ways you can test straightness you know there's lasers levels are a good one and that's the one we're going to talk about Auto collimators you know you can compare against a straightedge but what we want to what I want to do is let's let's use a sensitive level and actually check this machine surface and see how straight it is okay so we'll do a little we'll do a little lab we're just going to play around here okay so let me get set up here and then we'll we'll see how straight this thing is first thing we're going to do is clean we'll clean the surface plate if you haven't used this stuff get some this is the the best surface plate cleaner that I've ever used it has a little bit of I think it has lanolin in it or something but after you clean with this the plate is really clean in your instruments just glide on it like they're on a cushion of air which they are okay so one of my sayings is metrology is a is a dirty business and what I mean by that is is every Fleck of fly dust in [Music] speck of dirt and dust really impairs your ability to to take measurements so there is always cleaning all the time you know when you're when you're measuring things to close limits you you really have to be clean and clean the block you clean the plate look at that - that dark stuff that's just dirt and this this has been uncovered for actually was uncovered for about a day and because I was fooling around with something and and then I put the cover back on it but I always clean it every each time I use it all right I'll see okay so that's coming up pretty clean and it's just it's it's buff it out there it's just silky it's just silky now it's just beautiful okay so let's get our our straightedge up here carefully set that down okay and this plates not level I can tell you that and what we're going to do just going to use a little one to to kind of get things set up here so it looks like and we got to come up a little bit on this and so what I'm going to do is I'm going to put a couple of put a couple of adjustable parallels under here under the you know these under these holes which I think Jonathan set up at kind of the Airy points which are the points of actually they might be Bessel points because he doesn't care so much about the dent surfaces but what he does care about is the minimum amount of sag if this thing spanning over something so let's do that so there's two kinds of points arrey points keep the the ends perpendicular and vessel points have the least deflection on this surface all right so we'll put one under there I'm going to put another one under here and this will this will allow me to loop watch out there mister desert okay this will allow me to adjust it and get it so basically I'm just trying to get it close to level right now this isn't the fancy pants part okay oh that's pretty close better than that all right that's pretty good so see you guys maybe you can see that see that bubble and you can't see the bowl okay all right so now what we're going to do is we're going to bring out a different kind of a level and this is a this is an adjustable level here okay and what's neat about this one is even if something's not level we can actually zero it here because this tilts the tilts the bubble and we can actually take angular readings directly off of this so you can kind of use it in Reverse so you can you can level it on something that's not level and or you can compare two surfaces to one another you know this doesn't have a huge range but you can compare two surfaces so what we can do is we'll put it on one end and we'll zero it out nicely and then we'll slide it along and we'll watch what the what the bubble tells us here and this particular level has a sensitivity of one thousandth of an inch in 10 inches okay or a tenth of a millimeter in a meter okay so that's its sensitivity now it's not a super sensitive level but it's probably sensitive enough for this particular job and if we look at the bottom here we have two feet here basically they're separated by a distance so we can think of it as an angle change with the the base of the triangle being that distance between those two pads okay alright let me change the camera and so you can see down in there and then we'll play around with this so we get the level up there and then I just suggest a snob mmm so each each division is one thousandths of an inch in ten inches so if the tip of the bubble moves from one line to the next that's a thousandth of an inch over ten inches or 110 thousandths of an inch per inch okay so alright you can see that I'm not moving this very much and I gotta let it soak I'm looking at the wrong line is what it's sort of well it's actually pretty good okay so that's actually pretty good and I don't really care what the what the reading is on the dial here what I care about is what happens I want to lean on the plate here so if I lean on the plate too much you see that I'm pushing down on the corner of the plate a little bit the bubbles moving that's just how sensitive levels can be actually Richard King actually makes really good use of levels in some of his machine it when he's investigating worn machines you can tell a lot of things with a level that are hard to see with indicators and you know as far as overall geometry and twist and wind and all kinds of weird stuff so okay so I'm going to call that pretty good for these purposes here now I'm just going to try to scoot this down and not get it out of the frame let me go down maybe two inches let's say two inches yeah you guys can still see there make sure I'm still straight let's see what we got here I haven't changed the dial okay but you can see that now the bubble is not where it was right so what that means is there's a you know about 1/10 of tip somewhere in here okay so as we scoot down so if we measure this increment here we can we can create a graph of this of this curve so let's scoot down and we'll take some readings I'm going to give it enough time to settle out there get zero my two inches is not actually two inches and one inch and five-eighths eyeball was off well it looks like it's going to work out to the end there and it's not kind of even gonna call it zero I can refer you that's it that's about points live there - point for me that's - point five at that one and what I mean by that is it's down a half a division between the half a division bubble division all right so that's about it as far as I can go on that and you know ideally this would have a kind of a narrower base and then you could examine you know smaller areas but that's still kind of fun so let's see what that means maybe all right so here's our measurement reduction I guess you'd call it so we took the readings here here's the level so I'm saying that these pads are separated by six inches just to do it that way and if one division is equal to one thousand of an inch over 10 inches we can derive an angle from that so that angle is 1000 over 10 take the tangent of that and you get point zero zero five seven three degrees which is a pretty small angle it actually is about 20 point six arc seconds which is pretty dinky okay so then if we want to know what the angle change over six inches is what we can do is take that angle and you know it's proportional so we take the tangent and multiply that by six and we get six ten thousand seven over six inches so that's one division on the level over six inches is six ten thousandths of an inch which actually makes sense right so if we take you know so we can close the circle here so if we take that divided by ten right that's one ten thousandths and we multiply by 6 which is six inches we get six tenths so that closes that circle but there it is in the mat now what I did was I kind of did a plot here and this is by no means to scale okay it's just to kind of illustrate how the thing moves up and down all right so oops I didn't I didn't fill in the numbers here but so the largest was one division that's the largest deviation that we saw and all the rest were smaller and they were - which means the level was down on the heel or down on the the end where I marked it so it dips down initially and then it starts to come up slowly and then it kind of levels off and then it starts to drop off again so which is kind of interesting actually so it'd be nice to maybe flip it around and so that we can catch the end coming from the other direction to see if this is this curve is symmetrical so maybe a some derivative of how we had it supported - so you know we only have it supported uh adjustable parallel so it's possible that it had a bow to it that we were actually measuring with the level so this is this pretty cool stuff right that you can use a level and this one's not super sensitive here this is not my most sensitive one by any stretch but you can actually inspect flatness and excuse me flatness actually and straighten it so you can actually get you can get a couple things with levels that's what makes levels kind of cool right they're just one of these neat self-proving things and depend and how they're made they can be extremely sensitive so anyway is kind of fun and just kind of illustrating how you can use a level two to check the straightness of something this could be a machine bed or a welding table or a straightedge or whatever you to buy for if you want anyway I hope you like hope you guys like that and thanks for watching and talk to you later [Music] you [Music]

Channel: oxtoolco

Views: 73,359

Rating: 4.9119353 out of 5

Keywords: Level, Machinist level, Hilger watt level, Adjustable level, Metrology, Inspection, Cast iron straight edge, Richard King, Kingway, Machine tool reconditioning, Machinist, Scraping, Machinery rebuild, precision inspection, Practical metrology

Id: zx2sjNvNlM0

Length: 14min 52sec (892 seconds)

Published: Thu May 18 2017