Very much this.
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Engineering principle behind this type connection
- Thread starter Maplehead
- Start date
Very much this.
That's a great point about the short shaft tolerances. So much to consider when designing this thing.
I'm still baffled as to why the industry just doesn't come up with a great design and then bang out these ball turners for different sized lathes?
There appears to be a tool for every other use in the world for our lathes and mills but hardly any commercial ball turners. I don't want to be spending all my time making jigs and tools. I need to be spending my time making my guitar parts. Plus, isn't spending money on more machine tools why we're all here in the first place?
I'm still baffled as to why the industry just doesn't come up with a great design and then bang out these ball turners for different sized lathes?
There appears to be a tool for every other use in the world for our lathes and mills but hardly any commercial ball turners. I don't want to be spending all my time making jigs and tools. I need to be spending my time making my guitar parts. Plus, isn't spending money on more machine tools why we're all here in the first place?
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- Jan 31, 2016
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- 11,472
They do , they're called CNC lathes .
They do , they're called CNC lathes .
Lol
- Joined
- Jan 31, 2016
- Messages
- 11,472
If you ever do decide on what you're going to do and need bearings , give me a shout out . 
I have a box full up here new in their boxes . I know I have 6207s as well as smaller and larger . They come in handy for G jobs .
I have a box full up here new in their boxes . I know I have 6207s as well as smaller and larger . They come in handy for G jobs .Great, another expensive tool to go out and purchase.They do , they're called CNC lathes .
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- Feb 1, 2015
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- 9,622
With CNC lathes becoming more popular, there is little incentive to come up with a specialized radius turner for industry. The CNC lathe will do the job and much more.
Hobbyists are probably not a large enough market to warrant designing and manufacturing a specialty tool like this. We have a habit of DIY, especially when costs are relatively high. The Holdridge radius cutter was around for decades but very few of us would want to pay upwards of $1K. Shaplane still makes less expensive radius cutter for around $400.
If I were making your design, I would use an oil impregnated bronze thrust washer on the bottom and perhaps a ball or needle thrust bearing on top. A bronze bushing or pair of ball bearings would take care of radial loads.
Hobbyists are probably not a large enough market to warrant designing and manufacturing a specialty tool like this. We have a habit of DIY, especially when costs are relatively high. The Holdridge radius cutter was around for decades but very few of us would want to pay upwards of $1K. Shaplane still makes less expensive radius cutter for around $400.
If I were making your design, I would use an oil impregnated bronze thrust washer on the bottom and perhaps a ball or needle thrust bearing on top. A bronze bushing or pair of ball bearings would take care of radial loads.
Where is the placement of the bearing?
Do I bore out a space for it at the bottom of the cavity where the ball turner's rotary "disk" sits?
- Joined
- Feb 25, 2021
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- 3,130
My suggestion would be to take the bottom of the inner cylinder (hockey puck), relieve the center part and leave a 1/4" wide contact area around the perimeter of the bottom. Polish that perimeter using progressively finer sandpaper against a flat surface.. Put some grease in there. Then use a heavy belleville spring washer under the bolt head. This will allow you to adjust the holding force between the two parts with just a little bit of give. If that doesn't work then you can start redesigning with bearings.
The point is this design relies on the bottom of the inner male cylinder being perfectly flat, as well as the bottom of the recess you've cut. If the two surface aren't perfectly flat, then it is likely they are making MORE contact near the bolt. You want the contact surface to be at the very perimeter of the circle, and absolutely outside the radius of the cutter, as that reduces the rocking action. By cutting the bottom of the inner disc to be concave, you are preventing contact near the bolt, and forcing it to only make contact near the perimeter. That has the same effect as the longer axle verses shorter axle in the tolerances issue.
The belleville spring washer gives you a little more adjustment on tightening the bolt down so you get some significant holding pressure but not so great that you can't turn the disc. You may still have a slight bit of radial play, but just like backlash, it won't interfere with turning an accurate circle once it's loaded.
The point is this design relies on the bottom of the inner male cylinder being perfectly flat, as well as the bottom of the recess you've cut. If the two surface aren't perfectly flat, then it is likely they are making MORE contact near the bolt. You want the contact surface to be at the very perimeter of the circle, and absolutely outside the radius of the cutter, as that reduces the rocking action. By cutting the bottom of the inner disc to be concave, you are preventing contact near the bolt, and forcing it to only make contact near the perimeter. That has the same effect as the longer axle verses shorter axle in the tolerances issue.
The belleville spring washer gives you a little more adjustment on tightening the bolt down so you get some significant holding pressure but not so great that you can't turn the disc. You may still have a slight bit of radial play, but just like backlash, it won't interfere with turning an accurate circle once it's loaded.
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