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Radius ball turner

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I've been wanting to make a ball turner for quite some time. Well, this past week I finally got a "round 2 it"! My first tool holder attempt caused me to say some things, that I'm glad my son didn't hear...
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...but I managed to get it right the second attempt! I first tried mounting the base to the location where the compound rest normally occupies, but soon learned that I would not have enough room, between the radius turner and the lathes center line....
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On the right side of the pic, you can JUST make out the tip of the live center in the tailstock...so went back to the drawing board, and decided that I would remake the base, suited to mount on the cross slide...20190122_210105.jpg
Well, I deffinately had more clearance now, but something else hit me like a ton of bricks. I had no means of moving it forward or backward, something I didn't even consider since it was originally going to be mounted on the compound. Also, I really disliked having to use the gib from the cross slide, it was just SO oversized for this little 4" tool, so I decided to make it's own gib.

Well, this got me to thinking...there is no way that I am going to be able to keep up with that little gib, when the turner was not in use. My solution was to embed the small cut off section, that was cut in order to be able to use transfer screws to place my gib screws in the right location, with a few magnets. Viola! No losing the new gib now!

As far as for making the tool move forward and backward, I decided to make an nut that would ride on the original cross feed screw, and i was quite pleased with how well it turned out, not to mention it worked!!
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After fixing those few road blocks, I decided to gun blue the toolpost, and obviously had to change the color of the lock down screws, so there would be some contrast. That process, again, turned out surprisingly well....
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Only thing left to now, is mill the top of the tool holder down enough to accept an insert, and to put it right on the center line, then drill/tap the screw to hold the insert....and, oh yeah, make a brass ball for its handle!;)
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Anyways, thanks for looking. It was a fun project!
 

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I just finished one, also...

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I sort of copied Jim Dawson's design, except I used my existing boring bar holder for the block...

It works pretty well, using a modified end mill as a temporary cutter until I get motivated to grind a dedicated tool.

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-Bear
 
Would someone be kind enough to explain what drives the choice of axis orientation for a ball turner? The two in this thread are not the same, highlighting the issue for me.
 
Would someone be kind enough to explain what drives the choice of axis orientation for a ball turner? The two in this thread are not the same, highlighting the issue for me.
It is mostly a matter of personal choice, I think... the one that I used in tech school 20-something years ago was more similar to SubtleHustles design. I chose to build mine more like Jim's design because I had an extra boring head, so it was a matter of 'quick and easy' for me.

Either design is very effective, both have their own pros and cons...

-Bear
 
The major drawback for use of the boring head design is while it can do ball/convex shapes it can't do the opposite concave radii. The first design depending on where the cutter is positioned can do concave or convex. In my instance I need to do concave and convex so I'm gathering my resources to make one similar to the first design.
 
Very nice. A question though, when using one of these it seems the centerline of the pivot should be exactly on (and perpendicular to) the centerline of the spindle. How does one measure this to know when it is on center?
 
So the cutter is on the center height. You start taking cuts closest to yourself, not on center, and you move your crossfeed in slowly, between each subsequent cut. You will know when you've reached center, when your ball is completely formed. It's much like knowing when you've reached center during facing operations.
 
The major drawback for use of the boring head design is while it can do ball/convex shapes it can't do the opposite concave radii. The first design depending on where the cutter is positioned can do concave or convex. In my instance I need to do concave and convex so I'm gathering my resources to make one similar to the first design.
A Ball Turner made from a boaring bar holder head can cut both concave and convex parts depending on which side of the pivot you have the cutting tool mounted.
 
A Ball Turner made from a boaring bar holder head can cut both concave and convex parts depending on which side of the pivot you have the cutting tool mounted.
??????. That is true with the first type , but I've never seen concave cuts done with boring head type. Got pics?
 
??????. That is true with the first type , but I've never seen concave cuts done with boring head type. Got pics?
No I dont have any pictures but ive seen it done first hand on a HF 7x12 lathe if that makes a difference!
If you sit and think about the mechanics in making a ball on a lathe you will see that your tool needs to smoothly rotate around a "Pivot Point" (cutting edge facing inward towards the pivot point) in order to cut said ball. How far away from that pivot point you set the cutting tool will determine how large of an arc your tool can make which determines how big or small your "Ball" will be, correct? Now if you move only the cutting tool to the opposite side of the pivot point and then rotate just the tool 180° from how you had it setup for making the ball ( cutting edge facing outward away from the pivot point) you will see that the cutting edge will now face the work correctly and will rotate around the pivot making concave cuts in your work piece.

I hope that helps clear things up a bit without adding further confusion.
 
Sorry, this is just more confusion because you are describing how THIS WORKS:
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where I was talking about the boring head like THIS works:
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this is a boring head.
 
Sorry, this is just more confusion because you are describing how THIS WORKS:
View attachment 287078

where I was talking about the boring head like THIS works:
View attachment 287079
this is a boring head.
Which is Exactly what i am speaking about! Looking at the bottom picture of the boaring head with end mill....you see the cutting tool is to the right of the central pivot which creates the ball or Convex shape. Now imagine the endmill to the left of the central pivot and you will see the tool will cut in a concave arch. I dont know a better way to explain it other then both style tools work the exact same way however they look different because their pivot rotation "SEEM TO BE" on 2 different plains which is where I believe your confusion is coming from however you could mount your tooling anywhere along the 360° rotation of the chuck and it would work just the same because both ball turners are actually mounted at different degrees around the Same Rotational plain of the chuck.
 
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I picture the pivot point being at the end of the boring-heads centerline along its length and then if the tool is to the right of that center line and rotated up and to the left (towards the headstock) it makes a ball. Like the above picture.
If the tool is located to the left of the boringheads centerline and rotated up and towards the tail stick you get concave features.
 
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