Metal Lathe Tutorial 15: Parting

hello Internet my name is Quinn and this is blondie axe this is lathe skills a series of quick videos on getting started in machining this is part 15 parting oh yes the one everyone's been waiting for parting is such sweet sorrow and every beginner is terrified of it and every big in your struggles with it but I'm here to say you can do it even on small machines and I'm gonna show you how right now let's start with a quick note on safety parting is the one operation where I go ahead and wear a face shield because the failure mode for parting is generally the blade shattering and that's not something I like to have in the vicinity of my face so this is the one time I throw this guy on when I'm using the lathe and the second thing is your East stop button if you're new to machining you may have never hit this guy so I think like a fire drill you want to do it just so that you're comfortable doing it in case you ever actually need to you'll know what that feels like so I encourage you to just to fire up the machine and I give that guy a slap so you know how it feels and you're comfortable with shooting your arm over there because again when things go wrong and parting they go wrong fast and things are going to bind up and you're going to want to just be comfortable so given that guys slap when you need to so give yourself a little east up drill wait a minute if parting is so difficult why do we even bother I mean it's usually the last operation you do on your part so it's coming out of there late anyway so why don't we just go cut it off on a bandsaw or something like that well the reason that we do it is that it can often save you a lot of time for example if you are making multiples of a part on a single piece of stock often what you'll do is you'll chuck up the stock like this and the excess is going in through the spindle bore and you can make your part and then part it off and just pull this stock out make another one part it off and you can make a lot of similar parts very quickly that way another reason is that once you get good at parting it can often save you having to face off the backsides of your part because a good parting tool operation will actually leave you finish equivalent to what facing would give you which can be very very efficient and the other reason is it often times if you're making very very skinny parts like let's say you need a bunch of bushings or washers you might drill a hole down the center of your and then grab your parting tool and just part them off and the resulting parts are too skinny to reach uh canned face off the backsides of them so the parting tool allows you to lop off a whole bunch of washers or bushings in one operation and not have to worry about how to hold those really skinny parts for a second setup and parting is just fun and cool once you get the hang of it you'll actually enjoy doing it and it won't terrify you quite so much but it's still the scariest operation now if you spent any time in machinist forums you know that one of the most common threads is help me with parting and it's it's a it's the one operation that I think so is fear and dread into every beginning machinist so the question is why is it so difficult well first of all it's not super difficult but it is more difficult than most other lathe operations and for the simple reason that it's the operation that asks the most of the machine it's got this the thinnest margins for error so it's it's high tool pressure and it's demanding of rigidity and there isn't a lot of wiggle room anywhere you know with most other lave operations if your tool post angle isn't quite right or your speeds and feeds aren't quite right or your tools a little dull or whatever you'd get away with it and it's fine and you don't really know that you're maybe you're making the mistake but with with partying well that's where we separate the women from the girls because if you're doing anything wrong the machine will let you know usually by chattering and often by grabbing the blade and shattering it into the facemask that you are of course wearing so that's that's really the the key to parting is that the devil is in the details and you have to do everything right to have good luck with it so what is it about parting that makes it so demanding that all of your machining parameters have to be perfect or it doesn't work well look at this blade here it's got width this is not a single point cutting tool this is a form tool and form tools are really where the rubber hits the road on rigidity and cutting fluid and squareness and everything else so keep that in mind the parting tool is a forming operation not a single point cutting tool and forming tools are best left to the woodworkers here in the machine shop we're civilized and we prefer single point cutting tools now I'm by no means an expert machinist but I'm going to show you everything that I know about parting and I think a lot of the common mistakes that beginners make and the reasons people don't have good luck with this operation and just to make this point on this small bench top machine here I regularly slice chunks off of this three inch steel round bar and I have good luck with it and you can too now onto the tools of the trade parting tools basically come in two forms you've got your traditional ground style of parting tool which is just ground from a high speed steel blank like any other lathe tool then you've got parting blades and these guys come in high-speed steel forms and also in carbide insert forms starting with the traditional ground parting tool one of the advantages of this guys that you get a nice amount of thickness here so it's they're nice and rigid and the other nice thing about them is it's easy to grind profiles into them so you can control the rake on the front edge here and you can grind a top break into it which gives you a nice rake behind the cutting edge which makes this guy really good at starting chips which a lot of parting tools are not and of course it's also nice that these guys fit into standard tool holders and they're inexpensive and you can make one yourself out of any high speed steel tool bits dock that you have lying around and of course the main disadvantage to these guys is that they generally don't go very deep so we don't have a lot of reach with this guy but for from any parting operations this guy is great and these tools are also really great for non parting operations they're great for cutting o-ring grooves or you know giving yourself clearance when single-point cutting threads up to a shoulder you know those types of things so a very useful tool generally onto the high speed steel parting blades now this is my favorite kind this is the t-shaped blade you can see that the top edge is a little bit wider and then there's a thinner body underneath and this gives you clearance down the sides of your cut which I find very helpful when parting and like most parting blades this guy lives in a parting tool holder and we'll talk a little bit more about these guys in a second now these guys come in a lot of different thicknesses and the thickness is generally a trade-off between tool pressure and lateral rigidity this is a 1/16 blade and I like the thin ones because I have a small machine and I think it it is happier with these thin blades but the downside to this is you have to be wary of situations where you're going to have lateral forces that are going to want to flex this blade sideways and next we have the flat style of high speed steel parting blade and these guys have a tapered profile on them so if we look at the end here you can see that it's kind of a trapezoid and it's got tapered sides which gives you that clearance down the sides of the material when you're in the middle of the part operation which is nice and these guys also have top break to them which helps with chip formation and so these guys can be a good option as well and last but not least we have the carbide insert style of parting tool and these guys have a holder that's designed to go into a traditional parting blade tool holder and then it's got this replaceable insert at the top and this insert has generally a pretty sophisticated geometry in addition to top break there it's got some taper to the sides and you can see it's even got a relief in the center there which helps with chip formation and braking so these these guys are pretty sophisticated and many machinists swear by these like any type of carbide though it does ask more of your lathe so I think for a lot of smaller machines and hobbyist machines carbide may give you more trouble than good old-fashioned high speed steel so when you're starting out you want to try your hand at parting you might be wondering well which one of these should I try well you can tell by which ones I've blessed with tool holders the the ones that are my go-to s I'm a big fan of this guy for not actually for parting but for you know various types of forming grooving type operations and then for actual parting work I really like the the t-shaped blades but you know part parting tool selection is one of those things that machinists will die on a hill over and if you go looking for advice in any online forum you will be inundated with very let's say engaged threads about which one is best and why no other opinions could possibly be correct so what I would encourage you to do is start with one and try it out and if you don't like it then try the others and you will find one that works best for you okay let's talk about how you hold these things in your tool post Wow like I said earlier the traditional parting tool can live in any old standard tool bit holder that you've got lying around but the parting blades require a dedicated holder and these guys are pretty much the same they've got a clamp up here that pulls back and down with a single screw back here to lock the blade in place and this also allows you to slide the blade in and out for different depths the other thing these parting blade tool holders do is give you the correct back rake on that blade because the tops of these blades are flat you don't have a rake cut behind the cutting edge like you do on the traditional parting tool or the carbide insert tool the blade holder is doing that for you so that's the other reason that these guys are important now the gotcha with these guys is that the registration surface upon which the blade sits is always flat and the parting blades almost never are so depending on which type of blade you are using you need a couple of tricks to get the best performance and best results out of your parting blade in the case of the t-shaped blade because of course the blade is t-shaped hence the name the clearance areas here are gonna cause the blade to sit crooked if you just clamp it flush against this back here so some people will put this guy in the mill and actually just grind a slot for clearance for the tee area at the top what but what I like to do is actually just put a little shim back there a slice of aluminum can works really good just enough to shim it up so that the surface sitting against here is flat and is holding the blade vertically so that the clearance areas on the skinny part of the tee can do what they are intended to do and then similarly if you're using one of these tapered blades I like to put a little shim down here at the base of the blade so that the blade itself is held vertically on at center line and the tapered areas are tapered inward like they're supposed to on both sides to give you the clearance that you need for your parting and for the carbide insert blades of course they are very simple because all the fancy geometry is confined to the insert so these guys are just a flat piece of ground steel to give this guy a little home in the sky and all he has to do is sit flat in this holder and Bob's your uncle okay let's talk setup now the most important part of your parting setup is rigidity and of course that's always desirable in machining setups but parting there's just no wiggle room here your rigidity has to be absolutely on fleek or you will not have good luck so we'll work our way top down here obviously your tool post has to be tight if you're not always tightening your tool posting you are definitely going to die so please tighten your tool post next is to your compound take a good look at your compound make sure that it's not overhanging its slide over here because that's a Commons source of rigidity loss and lock your compound up good and tight if you don't have a compound lock you can probably add one just by tapping a hole in the side if there's no way to do that tighten up the game adjusters on it these guys you know you don't usually compound that much there's no reason for this guy to be super easy to move and you know for smaller machines a lot of people will actually just remove the compound completely and add a riser to your tool post that's something to consider as well so make sure your compound is locked up good and tight working our way down to the cross slide now this is the only slide that actually needs to move for this operation so you can't you can't tighten it up completely but make sure this guy is properly adjusted if if you're Gibbs are not really really well adjusted and there's any more movement here than there should be then make sure that you you remedy that before you try to do any parting and you know for a little extra little extra liquid courage I like to just you know snug up the lock a little bit just not don't lock it but a little light pressure on the Gibbs just gives you a little extra rigidity comfort there and to the bottom of our slide stack of course is the carriage this guy does not need to move during the parting operation so lock that guy down leave it locked you're good to go before we begin you want to make sure your parting blade is nice and sharp again this really matters for parting so the nice thing about these parting blades is that you can just keep grinding the ends off of them to keep them sharp and give the top a little loaf - just to make sure there's no burr rolled over edge on there and once this guy's razor-sharp to the touch you are ready to go you also want to make sure that the front edge of these guys is perfectly square so if you've got any kind of like an angle on this what happens is the parting blade these thin blades are gonna tend to push themselves laterally as they start the cut and that's going to cause binding as the blade gets deeper into the cut and that lateral movement and binding is what causes these blades to shatter and generally ruin your day so make sure that while you're sharpening it you're really keeping that front edge perfectly square next we want to get our blade depth set correctly and this is a another critical thing that I think a lot of beginners get you need as little stick out on this blade as possible and this is very very important so because of the relief angle that's cut on the Front's of these holders you can get quite close to a round piece so get basically as close to the stock as you feel comfortable doing and then bring this blade in until it's just at the center like that and that way you've got the absolute least amount of stick out on that blade that you can get away with and still get your operation done now if you're turning very large stock you can start with the blade pushed in like this and then once you get in a little deeper you can stop and extend the blade out a little bit and keep going and that will maximize your rigidity throughout a large part in operation alright next up is setting your tool height for the parting blade and this is another one of those areas where for you know for other types of lathe operations if you're not dead perfect you know a you get away with it it'll still it'll still work but with parting there's really no room for error here so your tool height has to be dead nuts on and the best way to do that is to flip your tool post around so it's facing your tail stock put a good Center in your tail stock and then bring this guy up here and make sure that that is the top surface of that blade is dead nuts on the very point of that tail stock now when you're checking this height make sure that your tool post is tight and the tool holder is tight in the tool post and that because all of those things can actually affect the height of the tool post so before you take your final reading as it were tighten everything down take a look if it's a little too high or a little too low then you can loosen it move it up a little bit tighten it down check it again now if you want to err one way or the other when setting that tool hide err a hair on the high side because that way when the tool pressure drives this blade down it's going to just put it more on center which is okay when the blade is too high the worst that happens is it doesn't cut very well if the blade is too low what can happen is the the tool pressure drives the blade down which if it gets below the center line of the stock you're on the underside of this curve now and what can happen is I remember this stock is spinning in this way so what can happen is the stock can climb right up on top of that blade and that's when they're really bad things happen that's when the blades shatter and machine jams up belt slip gear teeth break etc etc so yeah if if you have to err one way or the other err just a hair on the high side with this guy next up is squareness of your tool again for other lathe operations this doesn't matter very much but for parting it's critical that this tool will be extremely Square to your work because otherwise as this blade goes into the work it's going to become crooked with the cut that it's making and it's going to start to bind up and binding up is what causes all problems in parting so your tool post has to be absolutely square there's lots of good ways to do that you can snuggle it up to the face of your tail stock coil which of course is machined and a true surface what I like to do is put a machinist block on the face of my chuck and just give that guy the right angle and then just bring this in and with the tool post loose and it'll just snuggle itself up into square and then snuggle it up like that remove that block and then put the hurt on it yeah we're good to go if you've faced off the work you can also use the end of that because it's in principle as squares anything else is on the machine now but you can also use the face of the jaws if the stock isn't in there yet or if there's you know there's other ways to do it but just make sure that that tool post is dead-on square and good and tight next up is to choose your parting location and this is also important first and foremost you want to work as close to the chuck as you absolutely can and still feel comfortable the closer you are to this chuck the more rigid the whole set up is and again this is an area where when you're turning you know you might be able to work out here and get away with it when you're parting you absolutely have to be up in nice and close to this Chuck the best way to be comfortable with that is to simply bring it in as you know as close as you can and spin the Chuck by hand and if it's not hitting anything then lock the carriage down right there and it's not going to move you're not going to hit that Chuck if you're not hitting the chuck now and the carriage locked you won't hit that Chuck while you're moving now one thing to watch out for though is that there may be parts of the tool holder or things back here that stick out further than the blade does so make sure that you're not going to get into trouble when this blade is in deeper and all this stuff is now closer to those truck jaws and an easy way to check for that is to just throw your machinist scale on the outside of your tool holder and just bring it in and again you can give your Chuck a little spin there and that'll tell you for sure that nothing is going to hit next up is cutting fluid this is another area where with other lathe operations you might get away with not using it or not using as much as you should or whatever not so with parting you pretty much can't use too much of this stuff when you're parting you want to keep the the cutting area just constantly soaked as you're going so I like to just use it straight from the bottle and just kind of hold it over the parting line and just drip it in there pretty continuously you know at least every few seconds and yeah keep that area nice and lubricated so this is doing a bunch of things for you it's helping to carry chips out of that cut which is important with parting because you're creating a very small space and the chips have trouble clearing themselves out of there so this helps with that it's also keep making sure you have good chip action because parting blades don't make great chips not like a regular single point tool does so this is going to help with that it's going to keep your temperatures down in the part which is important when you're doing something like a big piece of steel you don't want anything expanding because when things expand you know the work might tighten on the blade or the blade might tighten in the slot you don't want any of that and it's also very importantly lubricating the sides of the parting area because again the the blade is going in and if it's going in pretty deep now the sides of that blade are rubbing on the stock and so it needs lubrication in order to prevent anything from binding or snagging or if you know if unfortunately your blade starts to wander a little crooked or whatever lubrication is going to save you there because if anything gets crooked or binds up or snags that's when blades shatter and yeah that's when things go wrong so cutting fluid definitely not optional and the more the better all right let's talk feeds and speeds now this is pretty straightforward actually for when you're learning to part we're on your machine as slow as it will go when you are first learning especially in steel there is just no reason to do this fast so I always start on a larger diameter part as slow as the machine will go and if it doesn't seem VB forming good chips then I'll ease it up a little bit and as I get closer to the center I will ease it up a little bit more but when I'm parting steel I probably never get above 150 rpm and I think the lowest this machine you'll go is 45 so just to start slow and work your way up from there all the parting drama happens if you're going too fast so slow and low that's the way to go for parting now down here on the feeds I strongly recommend when you're learning parting off to feed by hand because the the feel is very important parting tools are not great at starting a chip but they are very good at keeping a chip going so you'll feel it when you have the feed just right where once you've got it started you'll get these ribbon shaped chips coming out of the parting line and then you just keep easing in at that same pressure keep that pressure constant and it'll it'll feel good if you start to feel the cut kind of bouncing or the machines starting to labored you know intermittently that's when you know you don't have your feed quite right you're not keeping up with that continuous spiral chip that you want to make as the parting tool goes in a lot of machinists will swear that power cross feed is the way to go for for parting I personally don't like to do that I like to have the option to quickly ease it out and stop the cut if I hear something I don't like or I feel something I don't like but you know if you're feeling brave go ahead and try power cross feed I think the advantage of it is that it gives you that nice slow even constant pressure automatically and that constant pressure is really what you want when parting you don't want that tool to have have to be losing that chip and starting a new one and you know introducing opportunities for chat or things like that so that even pressure is really what you want and if you've got a good power cross feed that'll go slow enough and gives you good results then go for it but like say personally I like to feed by hand because that feel and that sound and having the option to abort it will is something that that I like alright let's talk in more partner that was a lot of explanation and a lot of setup but it really does matter for parting so let's actually do the deed here so I'm gonna come in here lots of cutting fluid got all my slides locked gonna start my machine nice and slow I know that my Chuck is clear of that tool post so starting at 60 rpm here and I'm just gonna ease it into the work and here we go you see that chip starting to form and you can listen to the Machine and you want to kind of hear a nice even load on there just don't be in a hurry and if you look closely there you can see that kind of ribbon shaped chip coming off of there that's really what you want you want those ribbons once you get that nice ribbon you got the pressure right so just keep it going just keep that fluid in there better your technique is here as well the better your your surface finish is going to be from the parting operation which is one of the main reasons that we're doing this I'm not just taking it to the bandsaw you can also back it out occasionally to clear the chips if if your slot is getting deep and the parting blade it looks like it's having trouble clearing the chips then just give it a little help because our carriage is locked there's no drama leaving that slot and coming back in it'll come back right where it was now getting that chip started again is kind of the exciting moment so going nice and easy can you find that surface again and it'll pick up that ribbon chip again and away you go you can see as that slot gets deep you know this is right around the time where if our blade wasn't perfectly straight or if something was binding or if the blade was crooked in that tool holder because we didn't have that shim behind the t slot you know all those little areas that we talked about this is right around where you find out if any of them aren't right I know where my II stop button is you can see the work that it has to do to clear those ribbon chips so never hurts to just give it a little help because you really don't want those chips to pile up in there that's that's a source of trouble just when you come back in again just ease it in real easy if you jam it in there it's gonna grab and again that work is gonna climb up on the parting blade and chaos ensues ease in there it'll just pick up that ribbon chip right where you left it I'm doing this in real time so you get a sense of the pace of it just not in a hurry [Music] I was on a production line I'd want to be doing this a lot faster higher spindle speed more aggressive but I'm at home in my hobby shop I'm in no hurry and I do not relish picking parting blade shards out of my face now as you get close to the center here I'm going to use the spindle speed up a little bit because the blade will start to push and not cut if the surface speed gets too low it's a little more surface speed really help so we're up to 110 120 rpm right there now when you get close to the center what's going to happen is at some point that little tiny nub in there is no longer structurally sound enough to hold the weight of that part off the end and it's just gonna break off and fall so if it's a part you care about stick a piece of cardboard under there something to catch it I don't like to stick my hand in there and grab it just put something for it to fall on so it doesn't land in the chip tray or get dinged up on your ways but yeah in this case I'm actually just gonna let it fall cuz the camera mount is hit away there and I can't safely get in there so I'm just gonna let it go take it out of the chip tray like a chump [Music] and you can feel when it's just about done you just we're just turning a toothpick right now metal toothpick like civilized machinists and there she goes [Music] alright you can see that got quite a nice finish on there it's not perfect but for a parting tool it's pretty good now you're pretty much always going to end up with this little nub on there so if you need to get rid of that you can either chuck it back up and face it off or just say it with a little 400 grit memory paper and you can take that little guy right off of there all right but real talk now even with all of those tips the parting is just not always going to go well the bottom line is there are some machines that aren't great at it you know I told you at the top of the show here that I was going to show you how to part even on a small bench my top machine like this but I'm not going to sit here and tell you that you're going to be able to part steel easily on a seven by fourteen you know Chinese mini lathe there are some machines that just can't do this even some big ones you know it's asking a lot of the rigidity of the machine is asking a lot of the bearings and the spindle so if everything isn't perfect in the machine you just may not have good luck with it but that's okay there's no shame in that now there's lots of good alternatives to parting so let's talk about a couple of those so first and foremost of course is just take the part out and take it over to the bandsaw that's you know a very easy option and like I said earlier it's you know you're probably taking the part out of the machine anyway so you know it's let your last operation you have to flip it around to face off the end anyway so just take it out take it over the bandsaw there's this isn't a contest to see who's the best machinist you know there's no shame in just not being able to part on your machine just to use the bandsaw if you don't have room for a bandsaw they do take quite a bit of room there's our good old friend the hacksaw is a perfectly good alternative the one thing I would say is don't use the hacksaw on the stock while it's in the lathe I know that is tempting but the thing is you know hacksaw is tend to jump out of the cut while you're going and at the end of the cut they tend to drop down and you're very likely to ding your ways or ding some other part of the Chuck jaws or the machine while using a hacksaw and you know personally I think that it's probably also hard on the spindle bearings your spindle bearings are not bench vise they are not designed to be used for whatever kind of stock holding jobs you might have for me this calculus is simple the spindle bearings in my lathe are the most valuable thing in my machine shop everything that I do the precision of everything I make depends on those bearings being perfect so why would I do anything that might be abusive to them so sure your spindle bearing some love take the part out of the Chuck put it in the bench vise where it belongs before you use this guy if you insist on doing it definitely do not do it while the spindle is running that is a surefire way to end your day by picking a hacksaw out of your spleen and all of those things I just said it but the regular hacksaw go times 10 for the border bands these portable band saws are some of the probably the greatest tool invented in our generation they are fantastic but yeah the temptation will be even stronger to use it on a lathe and the damage will be even worse when you do so I yeah keep this guy away from the lathe but these are amazing yeah a little love on the Emery paper and you'd never know which end is parted well at least from a distance if you squint a little bit so that was a parting demo on steel but when you're first learning parting I would recommend starting with brass brass is going to be a lot more forgiving and if it's much as much lower drama if things go wrong so I start out on brass and once you get comfortable with that then you can move up to steel and similar to other machining I recommend trying on 12 L 14 free machining steel first it's a lot more forgiving with parting as with everything else and you'll have much better luck with that learning curve so that is parting in a nutshell I hope you found this useful please consider supporting me on patreon there's a link right there on the screen and we will see you next time thanks for watching you

Channel: Blondihacks

Views: 192,251

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, mini metal lathe, mini lathe, mini milling machine

Id: PeHmee4tvYc

Length: 30min 57sec (1857 seconds)

Published: Sun May 05 2019