FIVE WAYS to find a hole or punch mark on your mill!

hello Internet my name is Quinn and this is bloody hacks this is mil skills series of quick videos on getting started with your vertical mill this is episode eight aligning the spindle to a hole or punch mark let's go let's start with the why as a beginner aligning a mill with a hole on a part might seem like a trivial thing but it's actually one of the most fundamental operations you end up doing in your setups it's a very common thing that you wind up needing to do there's a bunch of reasons for that first of all holes are often made on other machines you might have started on the drill press or on the lathe and now you need to come over to the mill and maybe need to you know create a feature some kind of a shoulder or a flat area relative to a hole so then you know you need to start by aligning the spindle with that hole so that you can traverse relative to that hole and get your feature where you want another common operation might be if you've got a part that you know you've bought or that came with some piece of machinery and you need to modify it in some way and again the hole is your reference maybe you need to enlarge that hole and you want to make sure that the new hole is properly centered where the old one is or maybe you're fabricating a bracket for something and you've got a hole that didn't line up and quite the right place you want to make it into a slot so you want to line the mill up on that hole so that you can mill out a slot or if you're working on apart from a print and if it's symmetrical on multiple axes it's quite common for the primary datum on the part to be in the center where often where there's a hole so if you've done some operations on this part and now you need to come back and do other operations you need to know where the center axis of the part is but now there's a hole there so you can't indicate on it in any useful way you don't necessarily want to edge find and then do the math to find the center because that's going to be less precise then if you can find a way to indicate precisely the spindle on the hole itself the good news is there's lots and lots of ways to do this all with varying levels of precision that we'll talk about and I'm going to show you a few of my favorites let's start with a very intuitive and simple approach which is I think most people's go to including my own and in most situations this works very well and that's to simply get a pin that's the same diameter as your hole and then put that guy in say a Jacobs Chuck on your mill and then we simply bring down the quill and manipulate the table until that pin goes down in the hole just like that now this seems intuitively obvious and for new machinists this might seem like as perfect as you can get what could possibly be wrong with this right well turns out there are a lot of sources of imprecision in this so if done well this method is precise - less than a thousandth but there are a lot of sources of error so most of the time you do this it's probably going to be a little less precise than that the most obvious source of error of course is that this whole thing depends on how well the pin fits in your hole and well in this case not that well so that's why I was able to get it to go in there so easily this is a quarter inch dowel pin and this is ostensibly a quarter inch hole but whoever made this hole did a pretty lousy job and that's not a great fit this is probably you know ten thousandths of play there so that's obviously a source of error we're not going to get centered - any better than ten thousands just because of that but even if this dowel pin was a good fit there's other sources of error it's gonna matter if you're holding this pin in a Jacob's Chuck or in a collet or other method Jacobs chucks are less precise and other methods of tool holding that's going to be a factor the precision of this pin is going to matter this just happens to be a piece of oh one tool steel that I've cleaned up the ends on but if you used say a proper gage pin it's going to be much more precise this pin might have a bend to it it might not be obvious but if you put this guy on the service plate if you see any light under it anywhere it's got a little bend in it that Bend could be half hour or more so all of these little sources of error are going to add up to where this method you know may end up only being say 5,000 somewhere in that neighborhood but for many many operations that's more than good enough and of course the obvious advantage of this approach is that it's incredibly fast here's another example where the pin is a very good fit in the hole it's actually tricky to get it in there so that is like yeah that's like at least an RC to fit there's no lateral play in that at all so this is obviously going to be more precise barring all the other sources of imprecision that I mentioned so let's get this guy in there see how we do so when the pin is a better fit this is obviously a lot trickier but you have pretty good feel on the quill hope there it goes now it's going in but I can feel that it's tight so it's not quite centered there's friction on one side or the other so I'm manipulating that a little more still tight there we go it loosened up so now that's gonna be quite well aligned that's probably within a couple thousandths and with any of these methods once you've got it aligned you want to go ahead and zero out your Dro and/or your hand wheels so that you can come back to this spot as you need to a common variation on this trick is to use a drill for this because while drills come in lots and lots of sizes and so you can probably find one that's a good fit for your hole so here's one that's a much better fit for our oversized hole than the quarter inch dowel pin was but there are a few mental traps to watch out for if you use this method with a drill the first of course is that drills are quite flexible so it's easy to be four or five extra thousands off and not realize it because the drill is simply flexing and the longer the drill is and the thinner the drill is the more susceptible you are to this trap the other common trap is that you might be inclined to use the drill that made the hole to realign on that hole however drills tend to cut oversize they are not precision tools by any stretch so the drill is always going to be a little bit of a loose fit in the hole that it just made and if you're new to machining that might sound like horsey talk but there's tons of reasons why drills cut oversize first of all again the flexibility that I mentioned it's fairly easy for them to wander in the hole and there are various techniques for minimizing that but the other common reason is that there are two cutting edges on the bottom of a drill and they're never exactly identical so one of them is always going to be doing a little more work than the other and that tends to push the drill slightly off course as it goes and the drill might just be bent or it might have some run-out in and it might be poorly made lots and lots of reasons again drills are not precision dimensioning instruments they're they are bulk removal tools so be careful about using them for a precision operation like aligning on a hole but hey in a pen it works and you've seen me do it on this very channel very recently and all of that is why I keep these guys around this is just a one tool steel that I've cleaned up the ends on as I said and you keep these and you know a lot of common sizes quarter inch 3/8 whatever if you're in the know metric shop maybe you have three millimeter five millimeter 10 millimeter 13 etc and these guys are gonna be not quite as precise obviously as precision ground gauge pins but they're gonna be a lot more precise than something like a drill or other methods and you're probably gonna find that 99% of the holes that you make are going to be one of these standard sizes anyway so take advantage of that and keep some pins around another good source of field expedient dowel pins is your transfer punch set these guys also come in a million sizes and unlike drills they're smooth all the way down which is frequently very convenient so once again you can just chuck this guy up in a collet or Jacobs check depending on the size and then we can use this guy to align on our problematic oversized hole and there she goes in terms of precision the transfer punch method is going to be between drills and dowel pins these guys are relatively precision made and the smooth sides are going to give you a more precise alignment they are still a little bit flexible because they are long but they are less flexible than drills because they are meant to be hammered on so what is the upper bound of this method well if you do everything right if you have a precision ground tool steel dowel pin that's a precise fit in your hole and it's mounted in a collet or even better directly in the spindle of your mill using an r8 tape or something like that if you do everything right then you can get within half a thousand on that hole using this method now why would you ever want to go to all of that trouble this is why one of the most common reasons to need to align your mill to a hole is to set up a rotary table you want your mill spindle to be exactly centered on the axis of rotation of the table and this is such a pain in the patootie that you will often see a rotary table hanging out down at the end of the mill table on many a machinists mill they've set it up once down there they went to all the trouble to do it perfectly they saved it slow occasion in the Dro and then they don't ever want to move it so a great Saturday afternoon project is to go over to the lathe and make yourself a very precision dowel pin that fits exactly in the center of your rotary table and then has an r8 or something that will go and call it on the other end and can be used to align your rotary table to say better than 1000 in mere seconds now what if we need a little more precision or if the hole is larger than the dowel pin method becomes a little impractical maybe you can't make a pin that big that will also fit in any type of tool holding in your mill so what else can we do I kid a kid I love woodworkers in that case it's time to get serious we start by putting away childish tool holding and go to the kaulitz this is your basic dial test indicator this is a half hour resolution but obviously the more precise indicator you use the more precise this method will be and we're going to use the round shank holder on the end of it here in a call it now obviously the end of the indicator is not in any way aligned with the spindle axis but that doesn't actually matter what matters is that the offset of that indicator tip is going to be concentric with the spindle as long as that indicator is rotating concentric to the spindle we can use it for what we're about to do now as with anything on the mill the more retracted and the more locked everything is the more precise this will be so ideally you'd want to lock your knee or your head and you could do this with the quill but ideally you would have the quill fully retracted and locked again for maximum precision but a lot of the time that level isn't required and this method is still going to be more precise than other methods now the trick here is that of course any indicator has a limited range of motion and so we need to get this indicator in the ballpark of being centered on that hole such that as this indicator rotates the indicator remains within its range of reading if it bottoms out or lifts off of the bore that we're trying to indicate on then all hope is lost and cats and dogs living together start stockpiling toilet paper so an easy way to do that is to simply bring the indicator down just above the hole like so and now you can rotate this guy around and see how close you are so you can move this way yeah and I can see him quite off in that direction so I'll go this way once you get to a point where the tip of the indicator is roughly the same distance from the edge of your hole all the way around now you can start thinking about going down into that hole and of course the arms on these guys are adjustable so we can just bring this guy in and you want to bring this guy in such that it'll be riding on the edge of your hole and the indicator will be within its range and not lifting off the surface or bottoming out at any point and once you get into that sweet spot on the travel of the indicator which is a little fussy to set up but now we can sweep around by rotating the spindle by hand and you can see that we're effectively measuring how far off of that bore the spindle is now how do we use this information to get aligned on the bore well that might seem difficult because we can rotate this guy arbitrarily and we get crazy readings all over the place the fact is the table only moves in two dimensions all we have is X travel and Y travel so all it really matters is what our reading is aligned with the X and aligned with the Y so what you can do is rotate this guy so that the travel of the indicator is aligned with the x axis on your mill now obviously if you're not perfectly aligned with the x axis there's going to be some error introduced by this step but if you're careful and align it by eye in both directions it's actually going to be pretty precise as you'll see so what I can do is make a note of this reading or if you like you can zero it in this position and then head on over to the other side rotate the eunich ATAR around paying attention to the direction that the needle is moving as you do this get it aligned with your x axis again so we were at 0 on the other side and as we came around the needle was moving clockwise so we're at 15 plus 4 were at 19th ow on this side so we want to split the difference between those two readings you want that needle to go down to let's say about there and then we'll go check the other side again well spin this guy on around come back there and we were at 5 and a half the other way and now we're on about seven and a half so we're getting close so we're gonna split that difference again right there so we're on 7 right there and then back around this way yeah we're on 7 there so we're looking good on the X and now we do this same exercise on the y axis you know once again I check the reading here after aligning it with the axis and makes it easier you can zero it on each move but now we have a problem go to flip it around the other way now what do we do well that's where our friend the inspection mirror comes in so you can see it when it's facing backwards but of course you're looking into a mirror now so you can get messed up on what direction the needle is traveling so this takes some gray matter to pay attention to what you're doing and after a few minutes of fiddling around with that we've got it yeah within half a year all the way around I can't show you all the way around obviously with the camera but you could fiddle around with this more and get it better than that you could at this point maybe switch out to a tense indicator if you really need it dialed in so this method is fussy but it is very precise at this point you might be thinking wow that was incredibly fussy and tedious and there has got to be a better way to indicate precisely on AB or some sort of dedicated special-purpose tool and then you started thinking of all kinds of crazy contraptions that would solve that problem trust me none of the ideas you're having right now work luckily people smarter than both of us have thought about this problem which leads us to the Cadillac of bore indicating options the coaxial bore gauge this is the distinguished option for the refined machinist or maybe you just have more money than time or you don't relish the idea of contorting your body all over your mill table for 10 minutes every time you want to indicate on a bore so let's look at this guy now just like the budget-conscious indicator option this guy also mounts in a collet in the spindle let's take a closer look at how this guy works because it is really very clever now indicators of course measure linear travel they're a clockwork mechanism right so what we need is a way to measure concentricity with a linear measurement device that's a pretty tricky problem so the way this guy works is there's a leg down here that rides in your bore and there's a little rocker mechanism here and that rocker mechanism is translating the horizontal motion of that leg into vertical motion in this indicator if you look at this gap right here as I do this you can see how the whole body of the mechanism is moving up and down so what we have here then is a way to measure horizontal variance using linear indicator and that's really what we need so how do we translate horizontal variance indication into concentricity the answer is we do it dynamically and I'll show you how that works here in a second but the setup is very similar to the dial test indicator you need to get the range of travel this leg within the range such that it will be riding on your bore surface but not being overextended in any direction and the tricky is unlike the dial test indicator this guy doesn't have that friction adjustment to where you can position the arm instead what they give you is a whole range of these little legs that you can install here so there are straight ones in all different lengths there are curved ones in all different lengths and these guys can be used to measure both interior and exterior round objects so the curved ones are typically for exterior surfaces but they also work for interior ones especially on small Mills because the trick with this guy is that you are using the length of the leg to change the range of travel of the leg so these legs are a lever your fulcrum is this little rocker mechanism here so the longer a leg on there you have the further this guy is sticking out the more range of motion you have at the tip of that guy for the same amount of travel on this rocker so the idea is you choose a longer leg for a larger bore and you move the head of your mill up to get the tip of it in the right position however on small hobby mills like this you often don't have that much room to move up so that's where these curved legs are also very handy for measuring larger internal bores on a small mill but officially these guys are intended for exterior surfaces so step one is to figure out which leg is going to give you the range you need for your bore and then position your knee or your head vertically in the right place to get that leg aligned on your bore surface to do this I use the same starting method as we did with the dial test indicator which is to position that leg above your bore and then rotate it and there's no risk to any mechanism here because we're not touching anything so you can rotate it and visually see by eye if you're describing a curve that's very similar to the circumference of your circle and then you can move this leg by hand to get a sense of how much of a range you have on that so that short leg was too short because it was entirely inside the bore and it wasn't going to be touching when we moved it down so we'll go up to the next size up leg and well here's the small mill problem this leg is too long and my head is all the way up so that's where we go to the small curved leg an easy sanity check here is just to move the leg by hand on opposite sides of your hole and make sure that the mechanism isn't going to bottom out on either side and then we can just use our leg down into the hole like so now in principle we could turn this guy and get our readings but of course it has the same problem as the dial test indicator did in that we can't read the dial when it's facing away from us so the clever compromise to that problem is that the body of the indicator is free spinning it comes with this little leg we can attach and then you just need something to hold that leg to keep the whole thing from turning you can hold it with your hand or I like to just put an indicator stand in there and that'll keep things in place so we have both hands-free now you can see how that leg is following the bore and as it does that that needle moves back and forth and remember that's measuring horizontal variance of that arm remember on the question of how do we convert horizontal variance into a concentricity measurement I said the answer was dynamically and that brings us to the craziest part of this tool which is that you run it under power now you don't have to you can turn the spindle by hand but generally running it at a low rpm when the variance is large and then a slightly higher rpm when the variance is small makes it easier and quicker to dial this guy in you never want to run it too fast probably 200 rpm is as fast as you'd ever want to run this guy so this is 50 rpm right here now what we're doing is we're looking at the swing of that needle and what we want to do is minimize the movement of that needle so you grab an axis any old axis and you move it slowly and you watch to see if the swing gets larger or smaller so it got larger there so I'm going to go the other way and as I crank this in I'm using the y-axis here you can see the variance is getting smaller the needle is swinging and what will happen is you get to a point where the needle will start swinging larger again and that means you've gone too far so it's time to stop with that axis if you still have variance then that means that the remaining variance is being caused by the other axis so it's time to switch to the other one so I'll go to my x-axis here okay the variance is getting larger so that's the wrong direction so I'll go back to the other way and you just fiddle back and forth with the two axes there's a little bit of an art to this but you'll develop the feel for it once you get good with this guy it's very quick to get this dialed in and once again when you get down to a small variance like this it's helpful to increase your speed a little bit so that's 100 rpm right there because when the variance is small it's easier to see the range of the needle change if it's moving a little faster you could fiddle with this and get it dialed in better than that but you can see that we're within half a tick here of travel on that needle and these ticks are half a foul axial offset so we're you know probably within 3/10 here of being perfectly coaxial with that bore so that's the coaxial indicator very sexy great tool if you can swing it they're not the cheapest things in the world but if you do this operation a lot it's probably gonna pay for itself in time headache and neck Crick's and here's a little pro tip you know sometimes the tool will fall out of the collet as you're loosening the drawbar and you really don't want to do that with this precision piece of measuring equipment so the foam from the box makes a great little insurance policy now let's look at a related operation which you often need to do and that's aligning your mill on a punch mark this is especially common if you are doing fabrication work or if you're doing manual layout you're often going to have a punch mark where a whole to be so how do we do that well one quick and dirty way is our friend the transfer punch again so similar to what we did with the bore we can bring this punch down and then very carefully but I just line that up with the pointy end of our transfer punch of course this method has many sources of imprecision in it so it's gonna be a good two maybe ten thousandths but for many operations that's good enough if you're just making brackets for a workbench you know fabrication level projects that's going to be just fine but of course you know this is a transfer point it's not a precision tool so it's very likely to have a bit of a bend in it or it might be leaning a little bit because it's so long it doesn't take much error up here to move your punch down here noticeable amount again we're holding it in a Jacob's Chuck another source of error so not the most precise method but very very quick here's a variation on that method which I like a lot and you've seen me use this on my channel put a number two center drill in there instead and then bring that down and then what you can do is first line the center drill up by eye and that'll get you pretty close and then once you think you're close put some light pressure on that guy with the quill just rotate it by hand in the end of that center drill we'll make a little machined divot and you can see visually if that divot is aligned with your punch mark and if you have scribe lines as well you can see if the divot is aligned with those and that'll get you within probably two or three thousandths and if you're off a little bit you need to move it go down and you make another divot and it'll recut your divot a few that until you're left with something that's lined up with your punch mark this method eliminates a lot of the sources of imprecision of the transfer punch method the center drill is short rigid and precision made and because it's short we're in close to the work so the knee is closed or the head is down low and the truth is always in the cut on anything in machining and so by turning that Center drill by hand and actually carving a little divot we can really see where the center axis of that cutter is winding up and by extension where the center axis of the spindle is I like this method a lot it's my go-to when lining up want to punch mark and as I said it'll get you within a couple thousands if you need better than that you probably shouldn't be using layout and punch marks anyway but there are a couple of other options one of the options that comes with most coaxial indicators is this option here the idea is you can put this hardened to point on a punch mark and then the combination of this built in travel here and the rocker motion of the coaxial indicator will allow you to read when you're centered on that punch mark I have never had good luck with these to be honest so I'm not a big fan and honestly don't really use it once again if you need this level of precision you shouldn't be using punch marks anyway now the old timers are screaming at their YouTube players because I've gotten this far without mentioning the original low-budget old-school way of doing this the wiggler I don't actually have one to show you but I can explain how they work and I'll link to a great video by mr. Pete that gives you much more detail they have a long pointer mounted in a ball at the spindle end and you run them under power and it flops all over the place as you might expect because it's mounted on a ball and you bring something in like a pencil and you use that to straighten out the rotation it has a gyroscopic action that wants to keep it on the center axis of the mill because it's spinning and so that gives you a much more accurate pointer than something like the transfer punch which might have a bend in it and so you can use that to align the punch with the pointer and you can also often get a ball end on them as well and much like an edge finder that ball has a precise diameter and so you can use it to touch the edge of a surface find that and then move in by the radius of the ball to find your edge skillful use of a wiggler can get you within one or two thousandths of being aligned so they're a great tool they do take some practice but they're also very inexpensive so check it out as another option that does it for mil skills today I hope you found something in here useful consider throwing me a couple bucks on patreon and we'll see you next time you

Channel: Blondihacks

Views: 94,300

Rating: 4.954329 out of 5

Keywords: blondihacks, machining, machinist, abom79, this old tony, vintage machinery, steam, electronics, making, maker, hacking, hacker, lathe, mill, woodworking, workshop, shop, model engineering, engineer, engineering, live steam, machine shop, metal lathe, vertical mill, metalworking, metal shop, jewlery making, diy, home improvement, resin casting, how to, do it yourself, do it yourself (hobby), ASMR, mini mill, mini lathe, tutorial

Id: YoN_MSuqzE0

Length: 28min 13sec (1693 seconds)

Published: Sat Apr 25 2020