Edgefinding techniques

[Music] hey welcome back today i wanted to talk about how to pick up a zero location on milling machine i shot this numerous times during projects but i think i never did a good explanation of some of the techniques that exist there apart from the good old edge finder there are other options you can use dowel pin and you can use this contraption which you will see in hobbyists use quite a bit this is just the ball bearing pressed onto a dowel pin and you can use a dial test indicator i'm skipping the heimer 3d probe and the rainshot 3d probe because these are the most affordable options when we're at the milling machine and we have a workpiece clamped up in the device usually especially if you're working already on a part that's finished and you want to add features you need to know the relationship of your mill spindle to the part and for that we use these devices let's set up a little demonstration and give each one a try i'm just using a 30 millimeter gauge block as a dummy work piece this is not a good gauge block so i'm perfectly fine clamping it here in the wise this is just one of my scrap gauge blocks so this is held firmly in the vise and let's say we want to touch off on this side and center our spindle of the mill over this edge over this over this short edge here let's start with the most simple thing that we have uh a dowel pin just a round piece of uh steel that has been ground if you don't have a dowel pin you can use an end mill too and put it upside down in a collet for example i'm going to hold it in a regular more steeper to collar than the spindle so old timers this is this is a lot of an old timer technique to be honest old timers would now use either a filler gauge or a piece of cigarette paper to touch off on the side here and i know that the cigarette paper i use is about 40 micron in thickness let's double check it yeah that's pretty much 40 micron and now you just hold the paper in here and you approach the work piece now we have our dragging paper here and we can zero out our dro okay just to be safe we can repeat this maneuver and check for repeatability i get about the same drag now and when i look at my dro i'm again at zero we're now not at our final position that we want we need to move over the radius of the pin and the thickness of the cigarette paper so the pin is 10016 which rounds up to 1002 and the cigarette paper is o 40. 10.02 divided by 2 plus 0.04 gives us 505 we move that over on the dro and we should be bang on the edge of the part now i'm choosing coordinate system one for our pin and then we can compare each of the each of the um edge finding techniques to each other so let's change to number two coordinate system number two and this will be the ball bearing edge finder this device one thing that i didn't do right now i didn't check for run out on the pin i forgot that usually if you did something really precise this way you would check the run out of the pin instead of using a cigarette paper you can also use a light source from behind and approach the surface you want to touch off with the pin with a flashlight from behind and watch for the light gap to disappear so here is the ball bearing edge finder this is a bearing with 22 millimeter od i think it will help if we put a little bit of a mark on here and we let it run at a thousand rpm so an additional mark on the on the bearing would help so we can better see what's going on i'm adding like four marks and we're just approaching until the bearing starts uh stops spinning there we go okay let's raise it let's check the diameter of this bearing slightly on the size but pretty pretty precise so we can consider this 22 millimeters uh 22 divided by 2 is 11 so we move over 11 millimeters and zero out the dro so now we're again at with the center of the spindle over the edge okay that was option number two let's go for option number three which is my preferred one most of the time it's a regular edge finder like this pretty much everyone sells these get a half decent one they cost like 40 bucks but they're worth it they repeat better than the cheapish ones and these are basically two parts that are held together with a spring and you have a sliding surface that needs to be a little bit lubricated with very light grease so that these parts can slide in relation to each and other way you use it you run it at about 500 to 1000 rpm and approach your surface here and once you make contact it starts to at first it it runs out like crazy and the more you approach the surface the truer it runs at the moment you bypass the surface with the center of the spindle it will snap to one side hard to explain easy to show so let's go coordinate system number three today we're going to run it at a thousand rpm so on this one the the pilot diameter down here is 10 millimeters spot on um so we move over five millimeters and call this zero again okay that was the edge finder the the nice thing about the edge finder is it's not susceptible to susceptible to a runout error you can chuck this in a drill truck and get the same precision as if you would chuck it in a collet or you can even put it off center within reason in a boring head to do edge finding that way so that's why i like these you can slap you you can throw them in pretty much every tool holding device on a milling machine and get good results with the with just a pin uh that's a little bit harder same goes for this one this needs to be running half decent true now for the most fun and most versatile way of edge finding on a manual or cnc mill for that matter a dial test indicator that's mounted to the spindle and i like to use my shop build indicator holder here that clamps directly to the spindle i have a set of drawings somewhere on the internet for free to download a pdf file and this just holds it to the spindle and is adjustable i like to set it set the indicator so it's horizontal so i can read it all the time no matter the position it's spun to i don't need a mirror i don't need to to move my head too much around the milling machine it's very simple that way and also i like the stylus to be a little bit ahead of the spindle axis like in my case maybe 10 millimeters offset and in this direction i like it i want it to be kind of centered to the spindle this is not critical for precision but it's just for convenience sake so we have now a stylus of a dial test indicator this reads 10 microns per division that spins on a circle with the spindle of the mill okay what can we do with this now not much for a beginning we can come here and drop this down and bring our workpiece in contact with the stylus okay doesn't help us much yet we know nothing right now now we can spin the spindle back and forth a little bit this helps us to find the high point and we do this so we spin this until we find a high spot and then we zero out either by rotating the dial here or what we can also do we can just move the mill table and move the needle that way to a convenient zero up there we zero out the dro in this position retract the tool or the spindle a little bit uh the quill or drop the table depending on the setup of your meal and spin this 180 degrees so we it would be nice to be able to touch off on the surface but we can't because we're touching off from this side so what can we do we can take a gauge block and hold it up against the surface we want to touch off on from the second side and extend the surface up then we just bring this in into contact a little bit find the high spot and crank it to zero at this point we are not allowed to touch the dial of the indicator anymore you can do that on the first side but not on the second side okay now we have an arbitrary number here this is basically the diameter which the indicator tip spins on we need to move over the radius of this dimension so we take x which is this axis and hit the half button which divides it by two then we crank to zero and we are there now we're spinning a circle right over over this [Music] old edge so that's the most basic way of finding one edge using an edge using a dial test indicator very simple the only thing that you need is dial test indicator you need one anyway you should do any precision machining and something that is flat on one side a gauge block is good parallel is good a piece of ground stock is good you can hold it up by hand you can use a c-clamp a small c-clamp or a magnet you can also use a magnet that has been surface ground on one side to extend the surface up and use that to touch off be sure to use a dial test indicator that is resistant against magnetism the mar ones that i use are labeled and magnetic these are not harmed by magnets some are so let's compare before we continue we will compare these four ways of touching off on this side surface here okay let's compare these methods of edge finding first one was our dowel pin in a collet and that's what we're going to use as a reference we will call that zero two was the bearing edge finder three is the wiggly edge finder and four is dial test indicator using the gauge block method to compare these techniques we will take coordinate system one which was our pin and crank it to zero and switch through the coordinate systems and see how much deviation we get so pin zero this is the ball bearing edge finder plus 15 micron difference to the pin location 3 is 20 micron difference to the pin and 4 is 20 microns difference to the pin let's write it down i already wrote it wrote it down here we go these three the bearing edge finder classic edge finder and dial testing here are very close together within 5 microns and i checked the repeatability of each one against itself at least once or twice and the pin is off i think we can say that these two techniques are the most reliable because they give a very good visual indication and are not susceptible to spindle run out they are only susceptible to the roundness of the circle the the bearings spin which is usually very small amount of error so this one and the dti and the spindle we i call these the most accurate ways of edge finding on a manual mill the bearing edge finder is surprisingly close it's basically just as good if the run out is okay the pin with with cigarette paper was not too bad either that's like 20 microns difference between the edge finder dti and the pin and that's not too shabby so that definitely works each of these techniques is absolutely viable works perfectly fine why not go for it let's add some let's try the the pin with a light gap from the light source from behind so we go back to our dowel pin and clamp it in the spindle using collet again here we are with light source from behind that introduces a lot of flicker and we bring the tool in closer and there's the light gap gone let's do a repeat run okay there are even more techniques old-timers will probably yell at me and just say use an end mill okay here's a 10 millimeter end mill and usually the technique is you take a piece of paper and once the end milk wraps the paper you're kind of there i'm not the biggest fan of this technique so the idea is to run to run the spindle okay at some point the end mill will grab the paper and transport it through there the only problem is now you need to know the diameter of your end mill in this case it's a four-fluter it's easy because we can measure it with with you know this thing and this is a reground end mill this is the amount we had to move over 4.88 this is the radius of the end mill plus the 40 microns of the paper here all of the things we did that's held in a collet match up exactly and all of them are about 20 microns off from the methods that are not exactly critical to run out this one is a little bit but those two are completely independent from the runout so i guess my collet here has a little bit of run out maybe check that okay let's see i expect about 10 microns of runout yeah and that's what we get which is perfectly fine for a regular car uh more steeper collar that's that's really not too bad but that explains but that explains the error we get with the collet held ways basically when when the pin is rotating it's uh 10 microns in radius bigger because it's running off center a little bit interesting huh but wait there is more another application for the dial test indicator in the spindle is of course to center on round features on a part so let's see how how you do that reasonably quick again i like the dti to be horizontal if possible so i can read it without a mirror behind the machine i kinda eyeball the spindle of the mill over the part i'm going to just spin with the indicator just eyeballing it then we do a rough centering a very rough centering we bring it down we touch off on this side and move and we just eyeball it to be in line with the x-axis doesn't need to be precise we make this zero by moving the x-axis and we zero out the dro and we retract then we eyeball it to 180 degrees like this drop it down again top shelf in x to zero on the dti again and then we have an arbitrary number here that we want to split in half and we hand crank this to zero and then we are already roughly centered in the x direction and we do the same in y but why why and retract spin about 180 degrees drop down move back and split in half move y to zero and now we're roughly over the center of the part now we can fine indicate it we bring our indicator down to make contact with the diameter we want to indicate on and now we can spin it in contact so this is -10 this is zero we split the difference by moving the axis minus five minus five minus five that's pretty good here we have minus four move it to minus five and then you manipulate that until you get your desired precision when you do a full spin with the indicator around the part and this is pretty much within 10 microns now and this did not take very long and i prefer this a thousand times over a indicaul indicator i have one i have this german made diakatour which is a very nice instrument very well made but it takes up a ton of c space and it's not more accurate than this it's a little bit more convenient because you can have the spindle rotate and adjust during spinning but compared to this this takes less sea height it's easier to set up and in my mind quicker so that's definitely my preferred way of centering on a round part you can also use an edge finder touch off here here center touch off in this direction center and repeat in x and you will get a very good result too but i think around a round piece is best indicated with with a indicator in the spindle rotate rotating on the spindle bearings around the feature you want to indicate okay another application is for the dtis of course to center onto stock if you want to find the center point of a complete part that's not necessarily round and the way i like to do is i have again indicator level slightly behind the axis of the spindle and we drop it down a little bit so you can make contact with the part we crank in until we make a little bit of contact here on the dti needle and we swing until we find the high spot that's here and we zero out the dti once double check yep still high spot and we zero out the dro swing the indicator 180 degrees roughly make sure it clears the part drop the indicator down crank in to zero without touching the dial find the high spot there we are high spot adjust to zero and on the dro we take our x-axis put in x and half that's our center now we can hand crank it to zero like this and now we're in the center of the part now swing at 90 degrees we do the same in the y direction move in until we make contact uh find the high spot crank into zero zero out y retract the indicator swing it around crank over drop down make contact find the high spot that's here crank to zero and half and we're on zero and that's within that's very close to the center of the part now we can double check this by moving the indicator so we measure on the other side on the opposite direction we make contact here we zero it out and we we swing to find the high spot okay it's still zero and we retract the oh that's clever so we drop it a little bit and we make contact with the part doesn't need to be a precise number we just want to make contact and we swing it for high spot zero out the dial retract the tool go over to the other side drop down find the high spot and the dial should read zero which it does within within reason and this shows me that we're in the x direction on center okay and sometimes it could be useful to have the indicator swing on a known diameter you could either use a gauge ring for that or you use the machine itself to set that diameter and for that you use you can mount the block on the table or in this case i will use this piece here and device and the idea is to drop down we pick up this side of the block now as i showed before with the of the gauge block hit zero swing it around move it over get in our gauge block make contact high spot zero and x half so so now we are spinning right over over this edge over the surface that's extended up let's say we want to set the indicator to a 20 millimeter radius fly flying circle that means we move this over 10 millimeters which you can do very accurately because we have on this machine a dro with glass scales on a machine without you you would use the dials or indicators engage blocks on the on the tableways and now we can adjust the indicator very nicely until it makes contact with our surface that that we use as a reference find our high spot like this i zeroed out the dial here on the indicator that means when the needle goes to zero this outside the outside of the indicator ball is exactly 10 millimeters away from the center of rotation of the spindle that's a mouthful and we can double check that let's do another example this is a 13 millimeter ring gauge let's set this indicator to 13 millimeter that's six and a half millimeter in radius techniques are uh jig bore and manual measuring machine techniques they work on a normal milling machine too just not as accurate don't expect to get micron accuracy that way on a normal milling machine okay now we have this at 13 millimeters radius now we take this out of the vice and we take a magnet and our ring gauge okay this is not a little bit hard to explain i'm dropping down into the board with the stylus and i'm moving in to zero and i retract it turn it 90 degree make sure it clears i move in move the table in until i get zero here and then i can spin the dial test indicator without crashing anything and i get 0 here i get 0 here i get 0 here and here so that now that i have zero all the way around on the dial test indicator i know that my 13 millimeter that i picked up on the gauge block by moving the axis over 13 millimeters is correct and why would you set your indicator to a certain uh diameter for example to measure a radius if you had a half blended radius and you wanted to measure the actual diameter of it which you can't because it's partial diameter you can use that test indicator that way to measure it that's all checkboard techniques if you want to know more well if you want to know more about these techniques go and find go and buy moore's book foundation of mechanical accuracy and host contours and surfaces those two books explain these techniques very well so that's setting the indicator to a certain diameter without having a ring gauge i just used the machine's travel to set this diameter and i confirmed it using this ring gauge if i have a ring gauge of course i can do it different or i can use a set of gauge blocks and do it that way there are many ways but i like this technique because it's a reasonable simple and doesn't need much equipment so i hope you enjoyed this brief column of edge finding techniques indicator edge finder stuff like that thank you all for watching thanks for the ongoing support really i really appreciate it and thank you all for watching i'll be back you

Channel: Stefan Gotteswinter

Views: 63,036

Rating: 4.9798455 out of 5

Keywords: edgefinder, edge finder, dial test indicator, DTI, kantentaster, 3d taster, wiggler, pin, kugellager, fräsmaschine, milling machine, jig borer, lehrenbohrwerk

Id: dMKLZEgh_SU

Length: 35min 51sec (2151 seconds)

Published: Sun Feb 14 2021