The Secret to Cutting a Ball On a Manual Lathe

today I'm going to show you a ball turning fixture I've built several years ago to use on my one manual lathe but before I get to that I want to tell you why I actually built a fixture like that what you're seeing here is part of an ultralight aircraft airframe I've been working on now for several years and the reason I built the fixture was for these connectors you see here now these connectors are made of a solid piece of 6061 t6 aluminum which is a a grade that's used quite a bit in general aircraft and you'll notice how the profile at the bottom there is convex what I did is I took a solid piece of this aluminum and put it in a lathe and I turned in a 1.75 inch diameter ball on the end and then i milled each end here down to a 1 inch width and then board a hole through the center plus a couple thousands clearance so it fit on this tube and then reamed out that Jerald and reamed out this end for lightness so that's why I built the ball making fixture for so I want to show you that and actually how you turn a ball and a lathe with it now I'm going to show you the setup - which is a little bit involved but if you stick with it you'll get to see how I how it actually forms a ball on the lathe so I think it's pretty interesting I figured you guys would like to see it - so let's go take a look at that fixture here's a better look at the ball turner this is all made out of just mild steel that's all one piece I used use the wire EDM to cut out this C frame right here and then this part here I'll show you why I made that out three different pieces and of course the ball here on the end was I made this entire piece here in the handle but I didn't make this and of course I made this ball on here and then attached it to the end I thought that would be a nice representation of what the entire device is for there's a couple of ways of approaching turning a ball on the lathe and this is the first approach here where you use a solid piece of material and you can see right now it's kind of a waste of material if you're planning a cut in the ball off of here you just wasted this entire piece of material now what I showed you on the ultralight those pieces actually look like this so I needed to have this material so I didn't have a choice most of the time when you're making a ball though you're gonna end up cutting it off right here slicing them off with a parting tool or bandsaw or whatever and if you're making a bunch of these you would actually want to use a removable Arbor which would be this piece down here with internal threads it would allow you to screw on a piece of material carve out the ball and then unscrew it and then attach another piece of stock and then repeat the process and then once you have your depth set on this and your tool settings you can very quickly change out a piece of blank stock and make you know half a dozen of these in no time most of the time in machining is spent on setup as any machinist will tell you but for the purposes of this video I'm just going to be making one of these and it's gonna look like this right here what I'm gonna start with is a blank like this out of aluminum and then this piece I will be carving the the ball out of it next thing I'm gonna do now is set some clearance between the back face of where the ball is going to be and the face of the Chuck jaws just give me enough clearance so the cutting tool doesn't end up hitting these at a few hundred rpm I made this ball turner so it could fit in to just about any tool holder on a dovetail type tool post okay now I need to adjust the the type of the cutting tool here and again try to get it this much exactly on center as I can with the center of the part here okay that looks pretty good one of the things that makes this radius turner a little bit unique is that you can adjust this tool to get more clearance in the back of the part so say whenever you're cutting a radius here whenever you follow-through to cut the back end you see the problems obvious here you can collide with the Chuck jaws so what I did was I made this entire tool post so it can rotate to the left or them to the right in this case would be the left so the tool can get to the back of the part before the rest of the fixture does and that allows you to keep this part right here this part from getting so close to the Chuck jaws it's a big safety thing so you'll see here I could bring that tool right in to the back of the part and you'll see I'm still I still have a lot of clearance between the Chuck jaws in the entire fixture I have about three eighths of an inch there before it hits so I know I'm a safe distance I could actually bring this part in probably another hundred thousand sore so I'm just gonna leave it there for now now what I need to do is adjust the clearance to the Chuck jaws and also set the radius of the cutter that disassemble this slightly this top handle comes off exposes that thrust washer this thrust washer by the way is nothing more than a piece of polyethylene ah it's a yellow milk jug in other words so poor man's Teflon they call it so so once I do that I can come in here it gives me clearance for the wrench here to loosen this up loosen up the top of the tool post I can loosen the bottom one just a little bit once I have the clearance set I go ahead and tighten up this tool post again and now the clearance is set okay next I need to set the the tool radius from the center now being the ball is supposed to end up at 1.5 it's actually going to be slightly under because I had to remove the extrusion marks here the mil marks so anyway I have to to get a 1.5 inch ball I need to set it a 750000 radius 7950 thousands of course being half of 1.5 and to do that I'm going to set the the cutting tool radius the tangent of this tool has to be 750 thousand away from the centre of rotation of this fixture so that be the center of these pins right here so what I'm going to do is take a ground rod where these pins are at and set this with a gauge block I don't have a gage pin as long as I need for this so I'm going to use a half inch reamer because it's precision ground to half inch so what I do I just slide these pins out of the way like that down to there like that just snug it up so it doesn't fall through the bottom side okay now I have a good reference point now the one thing you got to keep in mind is that I can't get to the exact center of rotation because this is a half inch so what I have to do is take the depth I want which is 750 thousands and if subtract the radius of the pin which is 250 thousands that leaves us with a half inch or 500 thousands I need to slide that nose up against that gauge block until the gauge block till I can have no movement the gauge block and then tighten it up a little bit like that just slide that gage block out of there to continue to tighten up this tool bit at this point now we are exactly 750,000 some the tangent of that radius on that tool to the centerline of pivot on this fixture now what I got to do is remove this pin and put the original pins back in place [Music] place the thrust washer and handle tighten our up as well okay now everything's set now that I have that I need to find the front end of the part need to know where my front stop is here now you'll notice that being this travels in a circular motion you're going to have a high spot so I'm gonna find that high spot and touch off on the front of this part okay now that that's that I'm going to set a stop on the carriage here so we can't travel any further in than what I have it set out right now now putting the tool out and then bring it back to where the stop was at all right at this point I could start cutting out the circle and that is how I make a ball on a manual wave now this thing's supposed to be inch and a half in diameter so let's see what it is the sake of simplicity I'll use calipers first here great on the money with that one but this would be a more accurate say right here so do we have one point $4.99 so we're thousands on there now keep in mind I said I'd take a little bit under to remove the manufacturing marks on the outer diameter so yeah it was it was measuring before I did this is measuring one point five oh three four five oh two so once I removed that I'm the thousands on there so let's see if it's an actual sphere you have thousands on there I hope you guys found that informative so if you did give it a thumbs up and also subscribe to my channel and I will be seeing you next video [Music]

Channel: Arnold's Design

Views: 312,180

Rating: 4.8562737 out of 5

Keywords: lathe, lathe turning, ball turning, machining, ball machining, ball, ball making, ball turner, ball turning attachment, ball maker, ball lathe attachment, ball cutting attachment, lathe ball turning

Id: mwuZwkn1MsQ

Length: 14min 39sec (879 seconds)

Published: Fri Nov 10 2017