Mini Lathe Operations #1: Facing

hi it's Frank who's from mini live.com first video of 2018 but I wanted to do an introductory series on cutting operations on the mini lathe some of you may have gotten mini leis for Christmas or recently and I hope to do this a little bit earlier like prior to Christmas but didn't get to it but I'll do it now in a facing operation we cut sideways across the face or the end of the round piece of work this is half-inch diameter aluminum and it's been cut on the bandsaw so you can see it has sort of a rough finish on it right now and part of the purpose of facing is to convert that rough finish into a nice smooth finish I'm going to use a three jaw Chuck for this operation I like to use the three jaw for most of my work just because it's quick and convenient I also like the Forge off about I save it for things that I can't do with the three jaw I'll be using the little machine shop dot-com it's a model 5100 lathe and this lathe if you aren't familiar with it it's pretty much the same as the other mini lathe except it has a larger spindle it takes a 4-inch chuck as standard rather than three-inch which is standard on most of the other mini lathes a quick comment and passing in case you see it and are wondering about it but I've replaced the plastic safety shield that goes over top of the chuck with a small aluminum one the plastic one that comes with the lathe tends to get in the way out here when you're trying to do certain operations if you're working up close to the chuck or even more so if you're working on a faceplate the real purpose of the plastic guard is to prevent you from accidentally turning on the machine when you have the Chuck key still in place in the Chuck and this little guard will do the same thing and when it's in the up position of course the lathe cannot be started take our piece of aluminum stock here and put it down in the jaws usually I like to take a little brush and clean up the jaws make sure there's no chips or grit in there they could keep it from seeding properly and for this operation since all I'm gonna be doing is working on the end here I want to set it pretty far back in the jaws and of course the farther back in there you said it the more rigidity you get but generally you want to avoid having the work stick out more than two or three times the diameter or it will start to flex a little bit it may not be much and you may not even be able to see it flex but when you're talking about dimensions of a thousandth of an inch or a few thousandths of an inch even a little bit of flex can affect your work now this mini lathe I've equipped it with a quick change tool post which I really like and I strongly recommend that you get one if you can or as soon as you can because they'll really make a make everything you do on the mini lathe a lot easier and you'll actually get better quality work because of the ability to adjust the height as well see but I have actually three different tools here of different types and I'll just show them to you briefly the one on the right here is one that I ground on the grindstone from high speed steel blanks this one is a prefabricated carbide tip that goes in a special holder this one on the end here on the left is actually a high speed steel insert these are pretty nice I like to use high speed steel on aluminum he usually does a better job of cutting at least on a relatively low speed lathe like this and carbide works great on steel and harder materials but usually doesn't leave as good a finish on aluminum but Bolla try it maybe one of each and see what happens just for comparison I'll start out with my shop ground high speed steel tool and it's a very simple grind I have a website mini lathe comm and if you look at tool grinding it will show you the basics for grinding this particular type of tool which I use a lot and someday I hope to get around to making a video on that and of course the big advantage of the quick change tool post is the height of the tool is already set I said it previously and the tool stays with the holder so that once you've got the height set in the future when you got to use that tool you just drop it in place and then lock it with this cam locking lever and it will be at the correct height but I'll show you what happens with the facing operations if it's not at the correct height facing operation like most operations it's important that you have the tool right at the center height of the lathe which is to say that's an imaginary line that goes from the tailstock to the headstock and it's the would be the center line through your workpiece so you want your tool right on that center line I mean you get ready to make a facing cut you have to have some way to lock the carriage down and there's basically two ways to do that one is to use the half nut lever and lock the carriage down to the lead screw but of course you have to make sure the lead screw is not turning and the other way is to have some sort of carriage lock and in this lathe I've built my own which I'll show you in a minute but let's talk for a minute about the locking the half nut lever back here on the back of the headstock there's a lever a three-position lever that controls the rotation of the lead screw but in this case I want the lead screw in the neutral position so if I turn the lathe on if you look down here you see that the lead screw is not turning spindles turning the lead screw is stopped that's the situation we want so that we can lock the carriage down to the lead screw and it will hold the carriage in place now ordinarily when the lead screw is turning when you engage the half nut lever you can just put a little pressure on it and as the lead screw rotates it around it'll lock in but when it's not rotating you may have to wiggle the carriage back and forth a little bit as you're engaging the half knot lever so that the threads on the half nut lever engaged with the threads on the lead screw the purpose of locking the carriage to the lead screw is that the cutting forces otherwise could push the carriage back away from the work and instead of getting a flat surface across here you'd get some sort of a cone-shaped surface as the carriage drifts away from the work now I've equipped my mini lathes with a shop-made locking lever here that also locks the carriage to the ways and that's actually preferable to using the lead screw so if you have an arrangement like this that's what you want to use if you look on the internet you can find lots of plans for different ways of doing that and the only difficulty is that a lot of maybe most of them require the use of a mill or if not a mill than some heavy duty filing to accomplish it okay now I'm about ready to begin the cut but you want to position your workpiece and you can now use the compound hand wheel to move the tool forward and backward if you need to adjust the point at which it's going to cut into the work but you want to take a fairly like no more than say ten thousandths or so if you take a little bit more it'll probably still work but if you get to the point where you're taking a thirty or forty thousandths that's probably going to be too deep a cut and the lathe may stall or you get a lot of chatter so I'm going to back this off one way you can adjust that if you're not confident with it is bring the tip of the tool up until it just touches then come out with the cross feed and then use the compound hand wheel and you can just dial in about ten thousands or whatever you're comfortable with and it's not going to be exact because the compound typically is at an angle so the depth that you read off of the compound hand wheel usually will not be the exact depth that the tool is going to move in unless your compound happens to be parallel with the ways of the lathe but with that Set let's go ahead and turn the lathe on now I'm going to use the cross feed or cross slide just turn that slowly by hand and make our facing cup I don't have a tech on or so I don't know what the actual RPMs is but I have the dial set here on the control to about if this is the six o'clock position and this would be about the 10 o'clock position let's take a look at our result here you can see that the surface is basically flat but there's a little nub there in the center and that nub tells me that my tool the tip of my cutting tool is either a little too high or a little too low usually with experience you can tell from the shape of that nub whether it's high or low and if it's low that note will usually be cylindrical but if the tool tip is a little bit above the center the nub will end up being more of a conical or sort of a mountain or cone shape in this case it looks like it's my guess is and I can't see too well but it looks like it's a little bit low and I'll use that as my starting assumption this is where an adjustable tool post or a quick change tool post is really handy I'm going to just loosen this locking nut here now I'm gonna unlock the tool and then turn this ring and that will raise the tool up just by a few thousandths I don't know exactly how much but one of the interesting things about a facing cut is you can actually use it as a way or a gauge to determine if the tip of your tool is on the centerline of the lathe if it's not it will leave a little nub but if you get it right on the center line then you won't get that nub there and that's what we want no nub okay with the height adjusted now we'll take another test cut yeah and it looks like I got rid of the nub let's take a closer look all right now as you can see there's no nub in the center and that's the way we want so if you get a nub you have to play around with adjusting the height of your tool either higher or lower now if you don't have an adjustable tool post you can get yourself a set of automotive feeler gauges and of course these are all if you're probably familiar with them but they are all marked with their thickness usually in thousands but they may also be marked in millimeter says these are anyway you just pick up a few of these usually starting with the thicker ones and then place one or two or three or how many you need to get the tool right on the center height of the lathe just take your stock tool holder and put your tool bit in here and then just tighten it down finger tight you can bring it up to the work and see approximately where it falls you know whether it's too high or too low now this is a 5/16 inch tool blank so it happens to be a little bit low I could have started with a 3/8 inch tool blank and it might have been a little bit too high I like to use smaller tool blanks in fact I often use a quarter inch just because they're quicker and easier to grind less metal to remove an even quarter inch will work fine on the mini lathe for just about anything so next you can do a test cut and see what kind of nub you get after tightening my tool bit in the tool holder and I'll lock down the carriage now take a test cut to determine whether the tool is too high or too level you know as you can see we get a little stock there and I could see clearly that it was too low so put a couple of shims under there and try again the trick you can use that may help you speed up the process to take your digital calipers and measure the diameter that little stock you need to make the stock long enough that you can get the tips of your calipers on there though alright and it's reading about 68,000 I'm going to try using a stack of shims that are half of that or 34,000 so that should get me pretty close but from my set of shims I've chosen a 22 and a 13 so that should give me 35 should put me pretty close to center now we'll just loosen up the tool and we'll put these shims underneath and then tighten back up all right so we'll tighten it up now and now I'll do another test cut okay well that worked out pretty well looks like it got us very close to on center and that may be all we need us do one more pass with higher spindle speed alright that looks pretty good now that we've seen what it looks like with a tool a little bit too low and the tool right on center let's just out of for the sake of demonstration here I'm going to intentionally raise the tool up above the center line and we'll take a cut and see what we get now you may even find if your tool is too high the nub in the center will actually prevent the tool from trying to go past the center when you're turning the hand wheel you'll start to feel a lot of resistance there so if you feel resistance as you're approaching the center that's a good indication that your tool probably is too high but if we zoom in now and look at close-up you can see that there's a very definite cone shape there so whenever you see that that's an indication that the tool is too high but using this knowledge about these little nubs that form here on a facing operation you can take advantage of that as a method to set your tool height and in fact the method I use most often for adjusting my tool Heights they'll just take a piece of scrap aluminum typically and make a couple of facing cuts and tweak my fine adjustment here on my tool height until I get a nice smooth face across there and then I lock that nut in there and that becomes my tool height so I adjusted my tool holder to bring that to light right on center and that's what a nice clean facing cut should look like one more thing you may wonder about if you're new to this is what angle should the tool be at relative relative to the face of the work and if you have the tool squared up against the face you wouldn't get a nice clean cut because the edge of the tool would be just rubbing against that surface for best results you'll want to use a tool with a slight radius on it and I like to use an angle between the tool and the face of the work of somewhere between about five and fifteen degrees but you can experiment and see what you find in your own shop for this next test we're gonna just do a basic facing cut but instead of the hand ground high-speed steel tool I'm going to use this factory made carbide insert tool it's I got three points 120 degrees apart [Music] well actually here again it's not too bad I think we got a better finish with the high speed steel tool this has little shows a little bit of surface roughness that's been my experience with the carbide tools as they work pretty well but they don't give you quite as nice a finish on aluminum this time all ticket cut using the high speed steel insert [Applause] let's Savannah take a look well that did a pretty nice job so I think you can see any of the types of tools will work all right I think the carbide tool maybe gave a little bit not as good a surface finish but with some experimentation you might be able to get good results with that now one thing I didn't mention is particularly with aluminum I often use cutting fluid and I like to use tap magic aluminum brand but it keeps the chips from welding to the tip of the cutting tool which can sometimes cause problems and in fact I just noticed that on this carbide tool here it looks like there is some stuff welded to that tip I think maybe the message here is that 6 or 6/1 aluminum is a pretty forgiving forgiving material and even if your tool geometry is not optimal you can still get recently good results but for the best results you'll want to use the tool with a slight radius on it but those of you who are steel workers I'm gonna take this gnarly piece of steel it was given to me by a friend it was cut from a long piece of bar stock so I don't I don't know anything about its history other than it sat in a barn for many many years but I think it's probably some sort of some variety of cold-rolled steel and has a saw kerf here where I started to cut it and then changed my mind for some reason it'll go ahead and do a facing cut on that and see how it looks turn the speed down see if I could get rid of some of that chatter but let's try turning the speed back up and taking a shallower cut [Applause] well that's not too bad it's actually feels quite smooth so just to show that you can do this with steel there we go now one other factor that's really pretty much a routine part of a facing cut is when you're done facing you end up with very sharp edges along here and if you're not careful or not fully aware you can cut yourself badly when handling this material doesn't matter whether it's steel or aluminum but steel is more likely to cut you the harder the material typically leaves sharper edges so I always like to touch it up with a file take that sharp edge off or use a tool which I'll show you in a minute but we'll first do it with the file when working in the tight confines of the mini ladies I'm sure most of you know you need smaller tools than you would on a big full-sized lathe but these are I guess four inch files and I like I like both of them but they're made by Nicholson but this one I find particularly handy because it has this sort of tapered blade that comes to a point or a nearly a point so it's able to reach into spaces that you might not be able to get access to with a wider one like this many years ago I had a picture on my website showing me filing work like this and a viewer of my website sent me an email which I'm actually quite glad that he did and said you know that's a bad way to use a file because your hand is extending over the rotating chuck so the trick here is to hold the handle of the file in your left hand then you can hold the tip for more control in your right hand but that way both of your hands are out here out of the way of the Chuck now you're still working pretty close to the chuck obviously and you want to be real careful by the way you should always have a handle on your file so you can get them cheaply and they last pretty much forever but they can save you from a really serious injury if the file were to be pushed back the tang of the file pushed back into your palm you'd be looking at some serious surgery so definitely invest in some handles and you can get all kinds just touching up this edge or breaking this sharp edge we can use a pretty slow spindle speed you don't need much speed at all to do it you know maybe 100 rpm so just take the file like so on that sharp edge that's all we need to do and now it's much safer to handle that but an alternate way to do it is to grind yourself a little tool similar to this one and you can use that for the same purpose justice with the facing cut we want to lock the carriage down so it's not going to move during this beveling operation or chamfering so and again we can use a pretty slow speed for this and you really only takes a second just barely touch that tool do the work and the job is done if you want to you can go a little deeper and actually put a chamfer or a bevel on that work so here's what we have now and of course it's much safer to handle now with that sharp edge go on and if you stuck this away in a drawer somewhere and forgot about it you reach in there you know a month later or a year later grab that piece of metal you can get cut without expecting it so that's I often when I have a piece left over I'm not going to use it for a while I'll just touch it gently with a file before I put it away in the stock drawer well just for fun to show that it can be done here's a odd shaped chunk of brass that I acquired from a junkyard probably about 15 years ago and it was sort of a sharp metal steak some sort of ground steak used by utility as I guess for some purpose but anyway it was a nice piece of brass and I bought it and I've used it for various projects in the years since then but I had these sort of blades on the side which I sawed off with the bandsaw but this edge or this face here has never been faced and so I thought it would be interesting just to put a facing cut on that and see how it goes we're getting a little close to the capacity of this three jaw Chuck and got to be real careful yeah that you aren't opening the jaws so wide that they don't have any grip on the scroll inside and they're gonna come flying out so anytime you're gonna grip something like this that is fairly large compared to the chuck it's a good idea to test your jaws and make sure that they're not near the end of their range where they might come loose like I'll set it back in there a little bit farther just to get the maximum gripping power of the jaws and I want to tighten it off all three scroll positions here make sure that's tight this is a heavy piece of material you definitely don't want that working loose noise check sometimes your work will get skewed in there good way to check that is as you're tightening the jaws rotate it gently and if it's skewed at all you'll be able to feel hopefully be able to feel that it's not locking up evenly and smoothly so another good thing to check especially on a heavy workpiece like this alright let's fire the lathe up here and see what this does what you hear there is the cutting tool hitting these ridges on the edge but the actual cut looks like it's a little deeper than I want to take so I'm gonna back the tool off a little bit if you hear that it's still not making contact all the way across [Music] looking good take one more pass speed it up just a bit there's still a tiny little stock there which tells me that the tool is a little bit low just to give you an idea of the size of this little nub here this is a number eighty drill bit which has a diameter of 13 and a half thousands so you can see that little nub there is really pretty tiny probably around ten thousandths or so maybe a little larger kind of makes me wonder how they make these tiny drill bits in cut a helix into them something to think about I guess I wanted to comment on the cutting speed or the spindle speed to use when doing a facing operation now the interesting thing about a facing operation is as the cutting tool moves in from the outside diameter to the inside diameter the speed at which the tip of the cutting tool traverses the material is faster out here at this larger diameter and it actually becomes slower and slower and it approaches zero as the tool only gets near the centre so if you stop and think about it you know the the speed at which a point on this disc moves past the tool the farther out on the disc that you get the faster it moves so on a small workpiece like this it's probably not too significant if you imagine the industrial setting where you're turning for example a large wheel for a railroad steam engine or something you know back in the industrial revolution days on the outer edge of the wheel the metal would be moving past the cutting tool very very rapidly and of course they turn those things at very low rpms I believe I've read that there are lathe mechanical type lays that were used historically that would increase the rotational speed of the work as the tool moved inward on a facing operation and of course nowadays a lot of this type of work would be done on a CNC or a computer-controlled machine in which that type of speed compensation is pretty straightforward to arrange and Bill into your programming but for the type of work we do on the mini lathe the speed isn't very critical at all and I usually start out you know with around 800 rpm or somewhere in that range and either speed it up or slow it down depending on the hardness of the material and other factors but if you look and listen you can tell quite a lot about what's happening and whether the the speed is working well or not and of course with the variable speed control you can make compensation on the fly and if you really wanted to get tricky I've tried this a few times if you have a relatively large diameter workpiece say four or five inches you could actually change the rotational speed like the automatic machines do except to do it manually so if something you might want to play around with but the good news is that the mini lathe for the type of work we do it's not a huge factor so find a speed that works for the material and the tool you're using and go with that well that wraps up our tutorial on facing operations if you like this video I'll be doing some more on other basic lathe operations on the mini lathe and if you subscribe you'll get a notification when those come out so thanks for tuning in and we'll see you next time

Channel: Frank Hoose

Views: 162,793

Rating: 4.918736 out of 5

Keywords: lathe, metal lathe, mini lathe, lathe operation, mini-lathe.com, frank hoose

Id: HLZ5Gt7DFNo

Length: 30min 40sec (1840 seconds)

Published: Tue Jan 02 2018