Ball Turning Device

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Conrad_R_Hoffman
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Re: Ball Turning Device

Post by Conrad_R_Hoffman » Fri Sep 15, 2017 2:12 pm

Pictures of mine here- http://www.conradhoffman.com/ballturner.htm

I find the hardest part of the whole thing is getting the tool position exactly right for a perfectly spherical ball. Not-quite-spherical balls are very easy.
Conrad

1947 Logan 211 Lathe, Grizzly G1006 mill/drill, Clausing DP,
Boyar-Schultz 612H surface grinder, Sunnen hone, import
bandsaw, lots of measurement stuff, cutters, clutter & stuff.


"May the root sum of the squares of the Forces be with you."

earlgo
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Re: Ball Turning Device

Post by earlgo » Fri Sep 15, 2017 5:37 pm

That very reason is why I built the fixture to fit on the ways instead of the apron cross feed. One can install the fixture, adjust the position lengthwise, tighten the clamps and start turning. Makes a round ball every time, subsequent to the first setup.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

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wlw-19958
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Re: Ball Turning Device

Post by wlw-19958 » Fri Sep 15, 2017 5:45 pm

Hi There,

There are time when I don't want to produce a true sphere.
For example, I was making a set of crowned pulleys for a
Dumore tool post grinder. The radius of the crown is the
same for all pulleys but they were of different diameters.

I equipped my radius turner with a removable pointed "center"
that is the center of the radius that can be used to set the
radius of the turn and when aligned with a center in the
headstock, it will turn a sphere.

Good Luck!
-Blue Chips-
Webb

earlgo
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Re: Ball Turning Device

Post by earlgo » Sat Sep 16, 2017 9:36 am

Excellent argument for the Radius turning device as opposed to the Ball turning device.
My dad's original fixture was a Radius turning device and it worked well but difficult to set up for turning spheres.
I fixed that problem.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

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liveaboard
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Re: Ball Turning Device

Post by liveaboard » Sat Oct 07, 2017 5:53 pm

But what about concave spherical sockets?
I was working on a jig for that but had to stop and wait for some screws [insert screws] and a little tap.
Never finished it, but when I do it will be on here.
If it works...

whateg0
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Re: Ball Turning Device

Post by whateg0 » Sat Oct 14, 2017 12:35 pm

Here's my quick and dirty tool. I've now used it for both internal and external radii. I was pleasantly surprised that it was rigid enough to do the job. I think that it helps to have more material back by the toolpost rather than the little arm that many like this seem to use.
Attachments
radius_tool-l.jpg
radius_tool-r.jpg
ball_crank.jpg
mach_jacks.jpg

earlgo
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Re: Ball Turning Device

Post by earlgo » Sun Oct 15, 2017 9:57 am

Nicely done.
I have seen kits similar and a commercial rig similar, too.
You seem to have fixed the flexing problem with your variation.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

RSG
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Re: Ball Turning Device

Post by RSG » Mon Oct 16, 2017 11:14 am

Earlgo,

I have to turn some curved pieces of aluminum that are 6" in dia. Not a complete ball but about 3" of the face. Any suggestions on the best method? I think a ball turner that size would be vary hard to work with no?
Vision is not seeing things as they are, but as they will be.

whateg0
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Re: Ball Turning Device

Post by whateg0 » Mon Oct 16, 2017 2:07 pm

I wasn't sure what to expect the first time, knowing that the cutting forces from metal should be much higher than for wood. But, using a short 4" long wrench on the hex head sticking out the top gave me real nice control. I think with a long enough lever, it would be fine. The problem that I would envision with one like mine in that situation is the effectively long stickout of the tool. Earlgo's should be fine like that, though. A friend of mine suggested that better control could be had using some sort of worm gear or like. I can't imagine the time it would take to turn a part that way, though. I guess it would be no different than turning a taper with the compound.

Harold_V
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Re: Ball Turning Device

Post by Harold_V » Mon Oct 16, 2017 3:15 pm

whateg0 wrote:A friend of mine suggested that better control could be had using some sort of worm gear or like. I can't imagine the time it would take to turn a part that way, though. I guess it would be no different than turning a taper with the compound.
Exactly. Metal, unlike wood, is removed in much smaller increments, and can't be "horsed", for many reasons. For the home shop, power and rigidity dictate that the cut will be slow, so adding reliable control to movement would be a good idea. Small radii or small diameters, not nearly as critical, as spindle speed can be quite fast.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

earlgo
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Re: Ball Turning Device

Post by earlgo » Tue Oct 17, 2017 8:54 am

If I read your implication, you are turning a dome on a 6" diameter part. Maybe not. Is there a sketch available?
The apparatus I made will only turn spheres up to 4" diameter and/or spherical surfaces with a 2" max radius. Turning a dome in the center of a piece larger than 4" diameter is not possible due to clearance between the cutter and the pivot.
Whatever you do will have to have a solid foundation and be strong enough to prevent chatter.
A few months ago one of the posters here showed pictures of an apparatus that cut large curves using the lathe cross-feed and a link tied to the lathe bed. I have forgotten who it was and don't know how to search for it. Perhaps he will pop up and explain it again.

--earlgo
Before you do anything, you must do something else first. - Washington's principle.

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WesHowe
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Re: Ball Turning Device

Post by WesHowe » Tue Oct 17, 2017 8:48 pm

I'm the guilty party, here is a link: https://www.chaski.org/homemachinist/vi ... p?t=104773

I never turned anything bigger than a four inch diameter with it, but only because I didn't have any large stock needs. The curve radius, as implemented, would easily go to a foot, convex or concave. The diameter would be limited by lathe characteristics, specifically the swing and the carriage travel limits.

I have also used a boring head, but large convex radii pose issues due to interference between the work and the head itself. A 3" boring head should do a 5 to 6 inch concave radius though, or more, by mounting the boring bar perpendicular to the mandrel axis. I used my little Chinese 6" MT2 rotary table to hold the boring bar, with an adapter to mount it to the carriage. I have seen rigs that would mount the boring bar mandrel to a tool post, never made one myself. Using the rotary table resulted in a much smoother cut because, as Harold was saying, you need to cut less (especially steel) than what you get pushing a tool bit on some sort of pivot.

While it is neither cheap nor fast, you can turn very accurate radii, convex or concave, on a regular lather with most DROs. I used that method to make a pair of dies, one convex and one concave, that were exactly 30 thousandths different radius and offset, to press curves in two axes in sheet metal.

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