Boring head Ball/Radius turner

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The tip of your cutter is already past the center of the chuck. You don't need to reach in any farther than that .Here is a rather shabby youtube link to the cutter being used.
[ame]http://www.youtube.com/watch?v=6ygtJFBRUOU[/ame]
 
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That's my goal, kquiggleI I have had to re-make the threaded adaptor for the boring head. i'm working on that now.
Though my lathe is a 7x14, should work for you, too!

Chuck
 
Brian, the tip of the cutter in the picture is in fact, too far past the center. I need to move it toward me at least 1/4".

Chuck
 
This may be a problem for use on small Lathes, the body of the boring head takes up a lot of available travel.
 
After spending the day remaking, and remaking some parts, I have come to the conclusion that RodW's original design of the body of the ball cutter was not without purpose. His design allows setting the body of the boring head back from the lathe center line. If I have to start over, my version will follow that design. My version, in its present form, only works if I swivel the topslide around to where the crank handle is to the right and the rear of the lathe.
I have almost finished reconfiguring my version.
I stopped when my back started aching. Tomorrow is a new day!

Chuck
 
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Can't help but notice the wearing of gloves and leaning on the headstock while the chuck is rotating, as well as a loose fitting t shirt not tucked in.

Paul.
 
Brian Rupnow said:
The tip of your cutter is already past the center of the chuck. You don't need to reach in any farther than that
Click to expand...

Brian, thanks for posting that video. I watched it after I had mine half done to give me an idea on how to use the darn thing! I thought it would be terrible if I got it made but could not work out how to use it!

Chuck, Brian is right, you only need to reach the centre of the work piece so you will be fine. It takes a while to get your head around the geometry but the spinning lathe means by the time you get to the centre of the piece, the back side has already been machined. You just advance the tool into the piece to take manageable cuts.

I have attached some PDF plans I did up but I ended up modifying the design without updating the plans. The plan shows the area the shaft passes through to be 76mm long but it only needed to be 50mm. I cut a T shape out of the block to achieve this and centred the dovetail on the leg of the T. From memory, I think the 19.6mm dimension became 28mm and I cut away about 21mm at the back. The 28mm step meant the head was recessed back as far as reasonable but the micrometer adjustment is always reachable.

Note the plans show a hole for a pin to limit handle travel with a stop that fitted round the hub but I don't think it is necessary and I left it off.

Hope the PDF helps for those attempting this.

kquiggle, thanks for adding my design to your collection. I will go back and look at your collection soon.

View attachment Ball Turner Plans.pdf
 
Rod, the present configuration does allow me to reach center, but limits the size of ball I can turn. I didn't measure it, but I will later today.
I think
I think I will re-make the tool post with an offset like yours to allow bigger diameters.

Chuck
 
RodW--I built a ball turner similar to yours today, using my boring head. It works quite well, but the brazed carbide boring tools I have leave a really ugly/nasty surface finish on the aluminum ball. I hadn't thought too much about it before making mine, but the forces which transfer from the turning part to the boring bar actually reverse when you swing over the top and start down the other side of the ball. I don't think boring bars were ever intended to take the forces in the direction that are being applied to them when used in a ball turner such as this. In the video I posted the link to, the tool being used has a radically different shape than that of a conventional boring bar. Have you done any experimenting with different shaped tool profiles, or are you getting good results with the inserted carbide tool you are using in your video?---Brian
 
Hi
Personal preference for cutting tool is a round nosed HSS tool with 4 - 5 deg top rake, 6 - 7 deg front rake and used upside down of course.
This will produce a very good finish on Stainless steel aluminum an mild steel. Take fairly light cuts and use cutting fluid.
I remove the toolpost and bolt the Ball Turner - Boring Head in is place. Just an idea that this may help for the smaller lathes.
The Housing was bored with the boring head mounted in the chuck so it is on the Centre Line.
A couple of photos show the boring head built from plans in "Model Engineers Workshop".

Eric

DSCF1845.jpg


DSCF1846.jpg
 
Brian Rupnow said:
RodW--I built a ball turner similar to yours today, using my boring head. It works quite well, but the brazed carbide boring tools I have leave a really ugly/nasty surface finish on the aluminum ball. ?....Have you done any experimenting with different shaped tool profiles, or are you getting good results with the inserted carbide tool you are using in your video?---Brian
Click to expand...

Brian, I have alluded to the problem you noted. I have some insert tool boring bars for my boring head but they have a flat on the shank which of course is on the wrong side so I reverted to the brazed tip stuff that I don't usually use. I think it is the last few passes that set the final finish so slowing down and multiple passes helps, but yes, the sandpaper is necessary.

Others I have seen have made a new boring bar with something with a fine tip like a DCMT tip that will cut happilly in both directions. Don't quote me that that is the right tip for the application. It would be worth reviewing that video you posted to see how he did it.

I had a look at the VMNG, VCMT and DCMT tips at my favourite Hong Kong supplier. I think the VMNG tip is probably the one to use as the cutting edges are square, not angled (does that mean no rake?) so they are probably better suited to an upside down orientation?

I have some small CCMT06 tips which might be worth playing with but I am not confident I could make a seat for them as I don't understand tool geometry.
 
Rod--Have a look at my post titled "Boring Head-Ball Turner"--I designed a cutting tool and posted the design drawing and show the good results I got with it.---Brian
 
Brian Rupnow said:
Rod--Have a look at my post titled "Boring Head-Ball Turner"--I designed a cutting tool and posted the design drawing and show the good results I got with it.---Brian
Click to expand...

Brian

Thanks. I did have a look at your ideas. I was wondering if it as worth looking at using a CCMT tool tip embedded in the end of a steel rod something like this:

boringbar_zps71e15ce3.png


The CCMT 06 has an 80 degree angle with 7 degrees of relief. I don't think it would be too hard to machine something like this up. You would still approach it from the side so you will make sure you get a ball not an egg. I think using the longitudinal feed with the tool on centre might be problematic making a ball as you would need another setup to start machining the back of the ball and make sure you stopped in the right place.

One day, I might give this a go. I think the cutting angles would work Ok.
 
Rod--I think that would work excellent. As far as approaching the ball--I think you have to approach it from the one end until half the ball is formed, then approach it from the other end until the other half ball is formed. As long as you set the tool height so that it matches the top of the piece when you have the handle straight up, no farther set up is necessary. Just don`t swing past center when forming either end. ---Brian
 
Inserts are often used for ball turning but they use triangular or rhomboid inserts not square ones. I'm sure I've seen one with a triangular insert in the end of a bar for use on a boring head. The holder wasn't cranked though (why would you do that?) it was just a straight bar, although the insert may have been presented at a slight angle.

Not the one I've seen before but a similar design:

http://i207.photobucket.com/albums/bb93/blacksmithden/Radiustool-bitholder_zps24d0901a.jpg
 
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