Boring Head-Ball Turner

[Brian Rupnow]

I recently seen a post by Rod W over on HMEM where he had built a ball turner, using a boring head. It looks like he did a very good job, and I got thinking of building one myself, with as few parts as possible. Of course the first thing I had to do was to see if I could turn an internal MT2 taper to suit my boring head shank. This exercise turned out successful, and was covered in a separate post titled "Turning an Internal MT2 taper". Now, I don't really need a ball turner. In fact, I had made one about 5 years ago, never used it, and ended up giving it away. Boredom does strange things to a fellow, and I ended up making a new ball turner just to see if I could!! To start with, here is the part which I made with an internal MT2 taper, with the outer diameter turned to 1". It is made from aluminum, mainly because aluminum is easier to work with than steel, and even more importantly, I had some aluminum the right size (1.25" outside diameter). if you plan on making one of these, probably steel would be a better choice.

 

[Brian Rupnow]

For the outer housing, I had a piece of 1.25" diameter cold rolled steel. My tool holders are 3.0" long, so I cut and faced a length to 3.063" long and drilled a 5/8" hole full length of it.

 

[Brian Rupnow]

Since I plan on holding this unit in one of my AXA toolholders, I needed to make a "tongue" which would fit into the holder, so I cut a piece of mild steel .825" x 1/2" x 3.063" long--

And then welded them together with my old Lincoln stick welder.

 

[Brian Rupnow]

Some pre-measuring had assured me that I could get the weldment into my 3 jaw chuck without having the "tongue" or the weld interfere with the placement of the jaws, so I mounted it in the chuck and then finished drilling and reaming it to 1" i.d. with a 1" reamer.

 

[Brian Rupnow]

So now we are up to a total of 4 parts, plus the boring head itself. The only remaining parts required are the collar which attaches to the end of the aluminum sleeve with the taper in it, and a handle. You will notice that I have turned the end of the aluminum sleeve down to 3/4" diameter. This is the end that extends past the weldment when the collar on the end of the aluminum is setting tight against the far end of the weldment.

 

[Brian Rupnow]

Here are all of the pieces, assembled and set up in a tool holder on the lathe. The collar is made from more of the same 1.25" diameter cold rolled, bored out to 3/4" i.d. and tapped 3/8"-16 three places at 120 degrees apart. The handle is a piece of 3/8" cold rolled x 8" long, threaded 3/8"-16 unc on both ends. The other two tapped holes are for 3/8"-16 set screws. In order to get the tip of my shortest boring bar aligned with the center of rotation of the lathe spindle, I had to turn the top slide around to the strange angle you see here, but it does allow things to end up in the right place.---(This is what happens to me when I don't model everything first.---I get surprised when everything is assembled.) Fortunately, it does all fit into the envelope that I have to work with, without having to remake or modify parts.

 

[Brian Rupnow]

And now, most importantly---DOES IT MAKE A BALL?? Well, the verdict is still out on that, but I think so. The half ball you see here was made with an unmodified brazed carbide boring bar. Not sharp, and totally the wrong shape for what I was doing, but yes, it did make half a ball. (With a lot of groaning and complaining). The tool has adequate travel to turn the other half of the ball as well, but I am going to have to create a correct shaped turning tool to finish the other half. I will make a tool from some 3/8" drill rod tomorrow. Fortunately, some other thoughtful soul has travelled down this same path and then put a video of it on Youtube, so I have a reasonable idea what the tool should look like.

 

[Brian Rupnow]

This is a link to a similar ball turner video, and I will probably copy the shape of the tool being used in the video.
[ame]http://www.youtube.com/watch?v=6ygtJFBRUOU[/ame]

 

[chucketn]

I got my version of the boring head ball turner operational today. I finally watched the video you posted, Brian, trying to figure out why it's not working. Looks like I'll be making a different cutting tool from drill rod as the boring bar doesn't do well at all...
Chuck

 

[Brian Rupnow]

Actually Chuck, after I went and checked, I see that my boring bar shanks are 1/2", not 3/8". After watching the video 3 or 4 times, I realize he is using a triangular carbide insert, attached with a single screw to what appears to be a home brewed shank. Since any balls I make will be aluminum or brass, I can probably get away with 1/2" drill rod, flame hardened and oil quenched. I wonder what the guy used for a cutting tool on the one you copied?----Brian

 

[Brian Rupnow]

After doing an in depth cutter analysis, I have decided that this is the profile best suited to the boring head/ball turner.



View attachment BALL TURNER CUTTING TOOL.PDF

 

[chucketn]

Thanks for the drawing, Brian. I will try to duplicate that profile on a broken 1/4" HSS mill cutter shank. I have a 1/2" dia piece of drill rod cut to make a holder for it.

Chuck

 

[Brian Rupnow]

 

[Brian Rupnow]

This is the cutting tool as roughed out on my mill. I will hand file the .063" radius which shows on the drawing. Then I will quench, temper, and do a final grind.

 

[Brian Rupnow]

And there we have the tool filed to shape, flame hardened, quenched, tempered, and stoned to final shape.

 

[chucketn]

I'd like to see/hear how it performs, please!

Chuck

 

[Brian Rupnow]

The new cutting tool works excellent. It leaves some very small marks on the surface of the aluminum but they are very shallow and polish out quickly with some 220 grit paper. The ball in these pictures hasn't been touched yet with sandpaper. The ball isn't a perfect sphere, but that's because I had to cut away yesterdays butcher marks left by the stock brazed carbide boring tool. Somebody asked what size my ball turner is---Its 2" diameter with an MT2 taper and holds tools with a 1/2" shank. (I was wrong when I posted yesterday that I would make a tool from 3/8" drill rod. It was actually 1/2" drill rod).

 

[Brian Rupnow]

And there we have it, girls and boys. Done like dinner!!! It works, and with proper set-up will turn a perfect ball. The whole unit fits into an AXA tool holder. The ball turner that I built 5 years ago based on Steve Bedair's design required that I take the top-slide off my lathe to mount it, so this is considerably more convenient. I will answer any questions people may have, but other than that, this thread is finished.---Brian

 

[rodw]

Brian, Well done and documented. I am quite amazed that a new chum like me inspired someone of your experience to perfect it. That makes 2 now.

Angling the toolpost is a clever way of gaining the clearance as that seems to have troubled some. Time is always an issue for me. One day I might revist the cutting tool but as you say, you don't often need to cut a ball. The fun for me was in the making of it just as it was for you.

 

[Charles Lamont]

I would just advise not being quite so careless with the polishing rag and the chuck jaws as the bloke in the video. Gloves are a contentious issue too.