How to cut a thread on a manual lathe (Intermediate method ideal for home workshop & hobby engineer)

friend of mine has asked me to make him a new axle for the front of his motorbike and as part of that I'm going to have to cut some threads on the lathe so I thought I'd share with you the process and method that I used for screw cutting on the lathe the method I'm going to use is what I would call a sort of intermediate method it's a bit faster than the beginners method and it's a little bit less risky than the slightly more advanced method I started by getting the shaft roughly to size before cutting the threads so I've got my shaft turned down to its final dimensions and we're going to cut a thread on this end here we're going to cut a 60-degree thread which is metric so this little tool here has got an angle on the end of it that's sixty degrees so the tool shape defines the teeth on the thread I've cut a little groove in just here so that when I'm bringing the tool across I've got a little safe space that I can stop the tool before it runs in to this next feature for screw cutting we want the machine running nice and slowly now for this machine that's 35 to 180 rpm having the machine running nice and slowly means we've got more time to switch off the feeds before we crash the tool into the part next thing to set up is the threading gearbox so we want the lead screw to be cutting a right-hand thread towards the chuck and we need to look up the thread pitch on the lookup table here for this is an m14 by 1.5 so 1.5 pitch tells me that the selected set here needs to be be s6w so that's be s6w finally we need to set up the thread dial indicator if I move the carriage back you'll notice that this indicator the numbers rotate okay now that's determined by which of these gears is on the shaft and to change them you just undo this nuts and select which gear you want and then that gear meshes with the lead screw and as the lead screws turning turns the gear turns the indicator so we want to cut a one point five millimeter pitch thread so that means we need the gear with 16 teeth and then there's this little number here which on this case is numbers one to eight the next one down one three five seven the next one down don't confuse it it's not fifteen it's one and five what that means is when we want to cut the thread we can engage the threading by switching on the half nuts in this case using any of the numbers one to eight so when this is spinning around we can start off thread when any of these numbers lines up with this little dimple so to actually engage and disengage our threading tool we're going to use this lever just here this is the half nut engage and disengage so at the moment I can move the saddle back and forwards freely and if I engage the half nut the saddle now is locked onto the lead screw so if the lead screws spinning that will drag the saddle backwards and forwards depending on which way the lead screw is going and then we disengage it and we can move it freely again this means that we can keep the machine running and disengage the half nut at the end of our thread and then just wind the tool back to the star there's a little bit more to it than that but we'll get into that in a second so let's have a go at cutting a thread shall we the first thing I like to do on cutting a thread is color in the area that I'm going to cut the thread on this gives you a bit more contrast between the cuts and the uncut material and shows up any mistakes really quickly hopefully giving you a chance to correct them the next step is to just bring the tip of the tool into contact with the part this is going to set your datum now I like to just move the tool back and forwards along the z-axis as I'm doing this so the tip of the tool scratches a line into the inked surface that way I don't go gouging it in too far and I just touch lightly there we go we then want to zero out and lock the dial on the x-axis so this is going to be our depth of cut so we're starting at zero on the surface and then we're gonna be cutting in positive now there is a way of doing this slightly more advanced way where you rotate the tool post and you use the compound but this is slightly safer slightly less likely to make a mistake way so we're ready to take a scratch pass now so the order of operations is start the Machine up with half nuts off okay so the saddle isn't going to move when you start the machine then you wait for your number to come around on your dial thread indicator when your number comes around then engage the half nut when your half nuts engaged it's gonna drag the carriage along cut the thread when you to gets into the gutter disengage the half nut with the scratch pass done the best thing to do now is just have a quick sanity check grab yourself a thread gauge and just line it up and check that what you've cut is what you want so 1.5 mil thread gauge that looks pretty good what you mustn't do at this point is just bang the tool in reverse and send the tool back the other way because you look because of the backlash in the lead screw you'll end up cutting a different thread on the return pass so the way around that is that we withdraw the tool in the x-direction or the negative x direction in this case so that it clears and we've already disengaged the 1/2 nut so then we can just wind the tool back to the start now of course because we're using the half nuts and we can move the carriage independently now you can leave the machine running while you're doing there obviously not checking with a thread gauge that would be a bit stupid but moving this back to the start you can do this with the machine running no need to switch it off saves you a little bit of time so now we're back at the start we can bring the tool in and put in a little bit of depth of cut this time put a naught 0.25 millimeter cut on so that'll take half a millimeter off the diameter right so I'll start the machine up again waiting for my number to come around nearly there nearly there ready and go and we should be now cutting along the same line that we've cut along on the stretch paths coming up to the end getting ready to pull the path nuts and half nuts off withdraw the tool bring it back to the start bring back the depth of cut so back to zero and then we'll go in are there another quarter of a millimeter depth of cut so that'll take us to one millimeter off the diameter wait for the number to come around waiting waiting and go so they're coming up to the end my hands on the lever ready and half nuts off right little test fit with a nut just to check it's right now made a little mistake here I need to go a little bit deeper but the problem I've got is I haven't made my gutter deep enough and my threading tool is now starting to cut into the root of the gutter now because we're using this method with disengaging engaging the half knot I've got a little bit more flexibility here using the the really basic method where you drive the machine backwards and forwards you can't do this because you'll lose your position but because we're doing this method I can now come in with a normal cutting tool sort out this gutter go back put my threading tool back in and with reasonable confidence go back to the dial and the threading tool should pick up and refined the thread so let's give that a go here's a little tip because I've swapped the tool out and done a load of other operations what I like to do is just put the tool back in get the Machine going and then do a cut without actually having any cuts on just to check that the tool lines up with the root of the thread so you really don't want to screw it up at this point so my numbers coming around slowly numbers they're nearly there now and engage so I'm just watching the tool to make sure that it lines up with the roots of the thread which it seems to be doing reasonably well and disengage so we'll just take a couple of finishing passes now and you're taking a little bit now just to smooth up the surface make the nice finish thread right just not the top soft I think we're about there [Music] little bit of a memory paper in a bit of scotch right at the end just helps to clean up the threads get rid of the toolmarks and you always end up with a few little niggles that you need to get rid of small toothbrush or a wire brush is really good for cleaning the little bits of swarf out of the threads before you test fit your nuts oh yeah finished thread let's give that a little test with a nut that feels nice now there's a couple of ways to do this the screw cutting on the lathe there's the beginners way where you drive it back and forwards and it takes forever good place to start if you've never done it before and I'd say that this is a sort of intermediate level of doing it it's not quite as good in terms of tool load as the more advanced method where you rotate the tool post and things like that but it's just as fast and it's slightly less risky now if you're just doing small threads like this and you're a hobbyist I think this is a good way of doing it if you're doing great big parts cut in great big threads with big tools well I use the more advanced method because it's going to reduce the tool load but small parts hobby hobby home workshop stuff I think this is a this is a nice way of doing it because like you saw I made that little mistake it's nice and versatile I could go in do a little operation with a different tool come back pick up my thread where I left off and I just carried on and no mistakes and we've ended up with a nice finished part that so I'll get this parted off and there's a little hole to drill in the other end and then I'll get it given back to the person it's fall you

Channel: Handmade Extreme

Views: 380,953

Rating: 4.8546071 out of 5

Keywords: How to cut threads on a lathe, handmade extreme, Handmadeextreme, manual lathe, home workshop, hobby engineer, cutting threads, screw cuttin, screwcutting, screw cutting, thread cutting, cut threads, metric threading, cut metric threads, how to cut a thread on a lathe, how to cut metric threads, thread cutting on lathe

Id: wvYQdi68074

Length: 12min 7sec (727 seconds)

Published: Sat Jun 06 2020