Lathe Compound Setup for Single Point Threading...Myths and Musts

hey guys Joel paczynski advance innovations here thank you for stopping by thank you to all my new subscribers and everyone that continues to engage me in conversation comments thumbs up everything keeps me motivated thank you very much I am grateful and flattered by your support today I'm going to post a topic that's going to take some stress out of some of your lives and infuriate to some of you so I hope that it's more of a stress reliever for a lot of you guys but I do welcome your challenges on this topic I know there's going to be a bunch of them please post them in the line below and we'll go back to fourth anyway I'm going to start on the board today and we're going to go over to the computer in a minute and I'm going to back up what I'm saying with digital models that pretty much proved exactly what I'm saying so the topic today is the 29 degree 29 1/2 degree 30 degrees setting on your compound when you're threading now if you're like me and every other guy that's ever run an engine laid you were probably told set your compound at 29 degrees 29 and 1/2 degrees make sure you got it lock it down or dear God the sky's going to open up and it's going to rain frogs and the apocalypse is going to happen and it's going to be the end of the world you know any number of good things is a going to happen anyway that being said here's the big question 30 degrees 29 degrees 29 and a half degrees what does it mean why do you need it do you need it and what's happening with the tool while you're cutting okay well let's start with 30 degrees since 30 degrees is supposed to be the magic fantastic everything is fine and happy setting let's draw a quickie little graphic down here I'm going to show you exactly what's going on with a 30 degree tool let's say here's the OD of your part here's your first pass I hope you can see that O'Toole first pass now the second pass at 30 degrees I just watched a video online where a guy the lazy machinist if you haven't looked them up look them up used a bunch of different color markers and it's just absolutely perfect the way to do it let's say your compound is set at 30 degrees 30 degrees being half the tool right because it's a 60 degree threat let's assume it's a 60 degree to end most of them are so your next cut moves the tool along this edge and there's your second cut now anybody that says well the tool is not cutting on the right hand side because it's set at 30 degrees well guys what is that I'm saying that as the tool plunges it's absolutely cutting on that side some people will say you're making this thread with the trajectory and the entire thread is being formed by this surface well if that was true you would think that you wouldn't even need that side of the tool so I dare anybody out there to take their 60 degree tool and split it and still cut a good thread without going in increments of two ten thousandths of an inch of course which time you'd be single pointing that angle and that's not fair that's cheating if the 30 degree movement were the trajectory of the cut and the compound is stationary on the cross slide you could dial in a 30-degree angle with a tool that looks like this yes you could do that but since the 30 degree movement is a depth movement and the trajectory of the cut is a helix you have right side contact even at 30 degrees it's minimal and it's regulated to the depth of the cut that you've dialed in but yes you have contact on the right side of your tool even at 30 degrees so what happens at 29 or 29 and a half degrees well once you draw that - you have the OD of your part I'm going to draw two of them here so you can see what's going on hopefully a little bit better than the last time let's say you're going straight in when you go straight in the chip load is exactly the same on either side of the tool now until you swing that tool around and make that chip load bias to the left side you will still have minimal minimal minimal surface contact here and the bias of the tool on the left hand side now we're talking this gap right here this calculated contact is tenths ten thousandths of an inch feather edge cutting but nonetheless you still have the depth of the cut on the right hand side and the potential for full side contact when you get where you're going so I'm going to show you these circumstances over on the digital model that I have prepared and maybe it'll be a little bit clearer ok let's take a walk over the computer take a look these are the two parts that I'm going to use for the demonstration the gray part is a single thread profile and the yellow part is your threading tool both of them are symmetrical 60 degree notches and both of them have a six thousandths of an inch flat at the tip and the root of each feature each part also has its own twenty nine and a half degree alignment plane for later on I'm going to constrain the threading tool so at the top of the tool is either with the top of that part and at the centerline of each piece lines up you can see that that's a very accurate tool is going in that knotch I can make it constrained exactly but for this demonstration I just want to illustrate if you're plunging straight in with your cross line and forgive my voice allergies or kick in my butt as you plunge straight in with your cross slide you can see the overlap area in gray here is your chip load so it's a very symmetrical very even chip load but a lot of surface contact which is the reason you've probably been told to set your compound at 29 29 and a half 30 somewhere there abouts nothing greater than 30 though because then you ruin the thread geometry the profile of your cut geometry and it's just not going to end well so do not go over 30 realistically you don't even have to hit the 29 anything close is good but don't go over okay that's what happens if you plunge straight it let's take a look at the myth that there's no right side cutting if you set your tool or you set your compound at 30 degrees I'm going to go back in and I'm going to align the right hand side of this tool with the right hand side of that slot and you can see that it's sliding like it's mated which in fact it is absolutely on the exact same plane and I'm going to slide the tool in a little bit to simulate a depth of cut there you go now the 30 degrees setting on your compound is the tool movement but it's not your trajectory of the cut if everything was stationary and you were back turning an angle then you'd only be using one side of this tool but since this is a thread this is a form tool and you absolutely have right-side contact here you can see it this minor section of the right-hand side of the tool the tip and the entire left-hand side now the cut is heavily biased to the left and your surface contact is reduced by about 50 percent or less so it's less strain on the machine less chance of chatter but the right-hand side is still making contact I'm going to go for a global interference check here this is where the computer was going to show me exactly what's touching and what isn't touching I go for a model analysis a global interference and I'll say compute and what I do I can almost guarantee that this little section here is going to light up the flat this entire side and then the wedge coming back so let's hit the compute button and see what happens oh there you go anything highlighted in red is what the tool load would be is what the chip would be and what the impact on the part would be if you took this cut on this part so here's your minimal right side contact I'll get that a little closer to the camera you can see that the tool moved in at 30 degrees here's your minimal right side contact here's your tip contact and the entire left side of your tool is now engaged as well so to say that there's no contact at a 30 degree setting is false as well the depth of the contact is restricted to how much you dial in of course but nonetheless this part of your forum tool is required to maintain a continuous 30 degree profile of your finished feature let's go set it on the twenty nine and a half degree plane and see what happens there I'm going to start from scratch I'm going to set the top of the tool even with the top of the park and now I'm going to set the twenty nine and a half degree datum plane which is this one right here that's lighting up to the twenty nine and a half degree plane on the part okay that I like now very much like what just happened with the thirty degree cut I'm going to go a little bit deeper with this particular cut so that I can emphasize the right side contact potential is greater at twenty nine twenty nine and a half degrees than it is at thirty degrees you're still going to have the cutting area on the very tip of the tool as you did with the 30 degree setting so we can expect to still see a very solid contact on the tip of the tool but the potential exists for a 1/2 degree contact area on the right hand side of the tool the tool and the cut are always going to be parallel so whatever the cut is it's going to be tenths of an inch not an actual tenth of an inch but at ten thousandths of an inch as compared to the depth it's a I think it's like a 15 to one ratio at sixty degrees so I'm going to take this tool and I'm going to drive this tool in relatively deep and we're going to see what the global interference is that's not fair let's back it off a little bit getting off everybody's everybody's argument is correct we should have solid contact up here like we witnessed in the 30 degree demonstration tip and full left-side contact but I say that this area around here is going to be highlighted as well because it's closer to the straight in plunge geometry than it is to the 30 plunge geometry or more similar to let's put it that way let's go back to the model analysis ask for a global interference and I'm looking for this whole right side here to line up and it sure did see the green there's your there's your interference the right side contact that twenty nine and a half degrees is minimal the tool and the geometry of the previous cut will always be parallel so as it moves in the cut is 99 percent bias to the left side but the right side still has this feather potential which could be so small that either the tool to flex and won't cut it refuses to cut it or you can like some other operators put tension on the hand wheel which is a really good thing to do because you don't want your thread getting drunk they call that so keep a little bit of tension on the hand wheel that's a very good solid practice and a very experienced practice but you can see you have a very large tip contact and then a very small potential for contact all the way through to the end of the thread so if you're new at this and someone says make sure you hit that 29 degree mark you know what get close get 27 28 degrees 25 degrees it really doesn't matter just don't go over 30 degrees and your thread is going to come out just fine if you have a very large rigid machine and you want to set your tool square onto the part and dial in with the cross slide I've done it that way for 40 years and I've never blown a thread of course industrial machinery is very rigid and you can get away with that so if you have a home shop or a smaller machine that has less rigidity than some of the bigger stuff throw the compound at an angle and have at it but there you go guys no matter what you set that compound on both sides of the tool are going to cut it just will determine how much of each side of the tool is going to cut but they will always both contribute to the final Java tree it's all I got alright guys well I hope that wasn't too boring but the whole twenty nine and a half degree thing naturally on a machine that's not very rigid the closer you get to thirty degrees without exceeding 30 degrees the chances are the better thread result you are going to have because the majority of the tool load not clearance is on the left-hand side of the cutting tool okay so twenty nine and a half degrees is not a bad idea but it's not critical and it should still cut or at least feather or definitely make contact at the twenty nine and a half but they'll kill yourself to do it because it's not necessary so if somebody says twenty nine and a half degrees and you want to whip it at 28 degrees 25 degrees it doesn't matter you're still going to get a good thread and the majority of your cut load is going to be biased to the left hand side of the tool that's all I got I hope that clears some things up by all means if you don't agree with this put it in the comment line below and let's talk about it but I think the demonstration that I just gave you is pretty rock-solid so anyway Joe paczynski advanced innovations Austin Texas thanks for watching you

Channel: Joe Pieczynski

Views: 79,981

Rating: 4.9471722 out of 5

Keywords: joe pie, joe pieczynski, advanced innovations, advanced innovations llc, lathe setups, lathe hacks, lathe tricks, compound setup for threading, Single point threading, lathe compound setups, machine shop tutorials, threading tutorials, How to setup for threading, Do I need the 29 degree setup, Thread setups, threading on an engine lathe, 29 degrees, Machine shop tricks

Id: PnH_oeOUps4

Length: 16min 58sec (1018 seconds)

Published: Tue Nov 29 2016