Chasing Threads on a Manual Lathe

hey mechatronics students um this is Andrew dahlin and I'm frustrated um I've been struggling trying to create a metric thread for a little project here this is a the surface grinding wheel and it's got I I'd like to make a device that's going to make it easier to install and remove this um the surface grinding wheel it's got a thread here so I'd like to do is create a little thing that I can push thread it in and it'll help pop it off of a taper that's holding it locked in place so I've measured it uh using you know my little thread gauge here and found out that it's a one millimeter and uh 25 the outside diameter is 25 millimeters and the thread pitch is one thread per millimeter so it's a 25 by 1 M metric thread so in trying to create this I've been nothing but frustrated because the threads that I'm getting well that doesn't help very much they're just ugly so let's take a peek at some stuff here that's my setup these are the threads that I've been getting here and they're just kind of really garbage so I haven't been very happy with the threads I've been getting and then of course you know I start reading and checking around um and I find out an interesting thing here's another example of the threads I'm getting off of this just really crappy so something is obviously wrong with this setup for me to be getting such ugly threads so in reading the manual for the lathe I came across some interesting stuff here that talked about cutting metric threads and this is what I've been doing wrong so let me thumb around here and find that page in the manual all right of course I'm not able to find it straight away now um but it talked about uh the thread setup so I had the right pitch and the right gears and everything uh but what I missed was one critical step and why can't I find it now so just bear with me while I there it is so in this page of the manual it talks about thread cutting and there's one critical ingredient here that I was missing to cut inch threads we're all good we're using the half nut and the thread dial like I had shown in the previous video but to cut metric threads the half nut must be continually engaged once started and um keep it there so I can't disengage the thread nut so this is what's called chasing threads so let's get into the details here on my setup so first off we're going to take a look at my gearbox over here and specifically I'd like to zoom in on the metric threads okay so here's my metric thread and I'm aiming to get one thread per inch or one thread one thread per millimeter that's what that stands for so according to this I want to have the knob set up for K and V so I've got that set up and then also for one thread per millimeter I'd like to have it set for a and C so AC and KV so let's zoom out here and check what I've got here so you can see my um my knob set up again it was one thread per millimeter A and C so I've got the ANC set and then for one I want K and V so K and again the knob is off here but I've got the correct setup there now let's zoom in on the change gears all right sorry for all this fancy camera work here whoa okay so in order to get this properly set up to measure I'm sorry to to cut that thread this is my gear ratios that we want to have set up these are the change gears so I I've got the 120 gear the 127 but what's different about the metric is that it's 42 and 42. okay so if I zoom over here take a look at the ones that are set up for TPI which is threads per inch that's this guy it still uses the 120 127 but it uses a 30 and then mostly a 48 gear for the majority of the inch threads per inch so I had to change out the change gears four metric threads and that's where you'll see this guy we needed to go with a 42 tooth gear and another 42 tooth gear and notice the arrangement or this one's riding on the 127 this one rides on the 120. so let's see if I can zip over with my camera and take a look at the actual change gears on the device here so I've really got to zoom out there we go these are the change gears that we're talking about so this 42 tooth needs to be riding on the 127 tooth gear the 120 tooth gear needs to ride on this 42 tooth gear and they are marked although it's a little challenging to read but yeah that's my 42 tooth gear so I've got the change gears properly set up and they're a little bit of a pain to remove and install um and I guess every lathe is going to be a little bit different so those are the change gears the gearbox is set up for that one thread per millimeter so let's go ahead and talk about how we're going to do this without engaging and disengaging the half nut we're going to chase some threads okay so I've got the everything set up here and a couple things I'd like to point out I've got the blue area here is what we would like to have our threads cut into uh and then I've got the other camera angle down here so I can show the controls that we're going to be using but with the half nut engaged we can't release the half nut so the idea of releasing it we get it to the end of the cut and then backing off the cross slide then is bringing that back to zero like we've done with the other applications that's not going to work in this case so what we need to do is to keep the half nut engaged all the time we're going to go ahead come across here cut the thread and then just stop the machine put it in reverse and back out of there okay so that's going to be the sequence is we'll make our scratch pass here you'll be able to see that I will stop the machine we got to really be attentive and may have to use the brake so that we don't smash this the threading tool past that Groove then once we stop it we're going to put the machine in reverse and that will back it up so that's the plan we're going to go ahead and begin to get this set up so I'm just going to make this first pass get it pretty close over here and we'll begin so as far as the the RPMs of the machine I want to have it set up for its slowest RPMs so we're set at 70 RPMs and so what we're going to do is to fire up the machine then we'll engage the half nut and once this is engaged we cannot disengage it so we're going to come in here and it doesn't look like I'm making a cut now so I'm going to slightly push this in till we see we're starting to take a cut there we go there we've got a nice Cut coming across there and at this point the thing I'm going to be doing is have my hand on the off lever over here and once it gets into the groove I'm going to stop it so into the groove There It Is I've stopped it put on the brake a little bit okay now I'm going to put the machine in Reverse to back out of that so I'm not adjusting the top slider cross slide or anything we're just going to reverse the machine actually I'm going to pull that top slide back just a little bit so I didn't do a scratch pass all the way and I don't want to have it cutting backwards so there we go it's just going to be a back and forth like this where we keep the threads engaged at all times and once I'm passed go ahead and stop and here I'm just going to advance my slide a little bit here and we'll go ahead and run it forward all right be good for me to remember what my numbers are at there but you guys can see what we're doing we're chasing that thread slowly but surely and when we get to the point where it's through I'm going to lift up and stop the machine and I may have to slam on the brake okay it's through and I didn't have to slam on the brake I'm going to remember that my cross top slide here was at .06 okay so I'm going to back this up just a little bit or actually it was a point zero seven eight anyway I'm just going to remember what that number was and we'll go ahead and reverse the machine now we're not doing any cutting so this chasing threads is a little bit strange but that's what we got to do with these metric threads according to this particular machine all right so we're reaching the end of travel and I'm going to go ahead and shut the machine off and I said it was point I haven't got a full cut on this yet so I'm going to go to the go to my Mark I'm actually going to go all the way to .08 and we're going to cut this thread so going forward all right got a little bit of a heavier cut to begin with but now at least we'll have a consistent thread all the way across and I'm at .08 inches again I'm just going to be ready once it gets close to its end of travel we're going to disengage the uh not the half nut but just again stop the lathe and we're through very good all right this time I'm going to throw a little bit of cutting fluid on there and again I'm just going to back off that that nut just a little bit so that I can reverse the machine so I'm not doing any cutting on this back cut I shouldn't be but it actually looks like it's cutting just a little bit so that's not good I shouldn't do any cutting on this back turn it looks like it was doing a little bit of work there so that's not cool should have backed it off even a little bit further okay I am out and I'm going to go back to this I was at .08 and I'm just going to bring it up probably about two thousands from there and we'll uh drive it forward throw a little bit of cutting fluid on there and we're taking another pass just about two thousand so it's a very light pass and we're just going to continue doing this chasing threads back and forth this is actually the first time I've ever done this chasing threads business so I'm finding it kind of entertaining and wait for it to get out and stop okay I'm gonna back my top slide out it was at uh .08 2 so I'm going to back it off a bit and reverse and on the back cut we're not removing any material and these threads are looking so much better than the ones I was doing before so that thread dial just was not designed to be operated for metric threads on this machine okay so I'm out I'm gonna go back to where my measurement was it was .082 so I'm going to move that top slide um 82 80 probably move it all the way up to about another 2000 so 84. I'm saying these numbers so I can remember them and we'll go ahead and engage forward 84. a little more cutting fluid and that thread is shaping up beautifully and I'm just going to take my time moving slowly back and forth and I think you guys get the idea so I'll pause the video here after this pass and we'll repeat our setup here in just a little bit or you'll see uh once I've got the threads closer to done and stopping all right so we're going to pause here all right there's not a whole lot of blue uh layout fluid remaining so I know I'm getting close to the end of my cut here so this may be one of the last passes but with threading it just take it real slow one of the things I took to doing here while I was going along was to write down my numbers on the scale and that helped me as I was jogging it back and forth to remember what was the last cross slide top measurement here so I've been watching this dial and recording that number as I go so here goes another pass this is it's taking off about two thousands and this may be one of my last passes here not again not a whole lot of blue materials Left Behind anymore so I think I'm getting really close that blue layout fluid it's kind of nice when that goes away then I know my threads are probably getting close to being done but I'll do a test fit here momentarily all right so it's out and we're gonna back the top slide out and reverse the machine this time once we get back I'll do a do a test fit and see if the the threads engage with the nut that I have so again this back pass I'm not doing any cutting here it's just keeping the nut engaged and driving it forwards and backwards across here only moving the top slide back when necessary okay so I've cleared it and I'm just going to move my half the top slide to where it was before it was at 92 so there we go at this point I'm just gonna oh shoot I have to back it off even further so that's great and I have to keep that nut engaged so I'm going to back it up further and do my test fit so we'll reverse here for a while this may take some time okay now that that's fully out of the way uh we're gonna grab the nut that we have here from the surface grinding wheel and we'll give this a test fit and see oh it's actually it fits like a glove absolutely beautiful so way better than my previous attempts and I'm much happier with this threading experience than I was with the um prior ones so anyway um that's that's a wrap on this one this has been chasing threads uh this grizzly lathe cannot use the thread dial when cutting metric threads we have to use this process of keeping the half nut engaged and then driving it forward and reverse and when we go reverse we want to back that cutter off a little bit so that we can make sure that it's not scraping along the back side so that's chasing threads keeping the half done engaged cutting metric threads on this grizzly metal lathe catch you guys next time

Channel: Andrew Dahlen

Views: 1,636

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Id: lapBBPnOt08

Length: 18min 11sec (1091 seconds)

Published: Mon May 01 2023