Type bearings for ball turning jig

[Maplehead]

Hi All
I'm making a ball turning jig. So I will have one part spinning on top of another part with an axle upnthe middle of the both of them.
Since it's a ball turning jig laying horizontal I imagine I use radial bearings as the load moves outward from the axle, not along the axle. With that said I am more focused on the top and bottom pieces. Do their horizontal plains touch? Does the top horizontal plain "float" slightly above the bottom horizontal plain as it rests on exposed ball bearings? The bearings I have now are the enclosed two-ring radial bearings. However, it looks like both the inner and outter rings are at the same height, which makes me think when they are recessed in but sandwiched between the two plates that they would not turn. I envision only exposed ball bearings allowing the sandwiching of the two plates.
Your thoughts?

 

[SLK001]

I would use a pair of automobile front wheel bearings. You'll have to devise some sort of chip shield, as these bearings are not sealed. To give the clearance, just set the outer race shelf slightly less than the overall height of the bearing.

 

[Maplehead]

I would use a pair of automobile front wheel bearings. You'll have to devise some sort of chip shield, as these bearings are not sealed. To give the clearance, just set the outer race shelf slightly less than the overall height of the bearing.

This jig is probably way to small for those bearings. The surface diameter of the base and the tool holder are only 1". So the OD of whatever bearing I use must be less the 1". Everything online about bearings is all about their relation to an axle. I get that. What I want to know is about the two mating surfaces. The tool holder's bottom flat surface must rotate on top of the base's flat surface. So, what type bearings? Thrust needle roller bearings look like the type but they are used for axial forces. I think the tool bit pushing into the work piece is going to create radial forces.

 

[Winegrower]

I bought a pack of 51104 thrust bearings just for having on hand. These are balls instead of rollers, and I think the race will resist radial forces adequately. Check these out. They are a buck apiece.

 

[RJSakowski]

A ball turning jig doesn't need sophisticated bearings. There is no high speed rotation involved and the total number of partial rotations is small. A simple bronze bushing will work fine. Bushing are capable of dealing with high radial loads. We use them on crankshafts after all.

 

[Maplehead]

A ball turning jig doesn't need sophisticated bearings. There is no high speed rotation involved and the total number of partial rotations is small. A simple bronze bushing will work fine. Bushing are capable of dealing with high radial loads. We use them on crankshafts after all.

So a bushing and then just grease in between the surfaces?

 

[C-Bag]

I didn't even use bushings. Mine is all slip fit. With way oil on everything. No chatter, no muss no fuss.

 

[BGHansen]

Look up "Holdridge radii cutter" for what's one of the premiere accessories. I've seen one up close at work, had what looks like a bronze bushing at the top/bottom of the yoke. I don't know if that was "as designed" or not, may have been modified in the shop. Like RJ said above, it's not spinning under load like a rotating shaft.

Bruce

 

[bill70j]

I would use a pair of automobile front wheel bearings. You'll have to devise some sort of chip shield, as these bearings are not sealed. To give the clearance, just set the outer race shelf slightly less than the overall height of the bearing.

Agree. That's what I used when building the "Holescreek" model." But the tool carrier plate comes in at 3.5"D

 

[markba633csi]

Bushings gets my vote too. Don't even need to be the fancy sintered type. Just plain brass would be fine since the speed is essentially zero
and if the footprint of the tool is small then all the more reason to use a compact bushing arrangement
-Mark