Type of bearings used in the articulating arm hollowers

[Dave Schell]

I'm in the process of building my own version of a articulating arm hollower for my Vicmarc. I'll post some pictures when I'm finished but in the meantime I'm wondering what type of thrust bearings to use for the joints. Looking at the MSC catalog, I see I have a choice between needle bearings or ball bearings. Does anyone that has the Elbo tool or Monster tool know what kind of bearings are used in those hollowers?

Here are pictures of my choices:

[Alan Trout]

I am not sure but I suspect they do not use thrust bearings but instead use a radial load ball bearing that is press fit into the part. I just got my monster rig and have not taken it apart, but that is my suspicion the way it is built.

good Luck

Alan

[Stan Terrell]

The elbo tool uses the one on the right.

[Bill Bolen]

the one on the left is the one I used on my home made steel snake. I think it took 9 of these...Bill...

[Rob Cunningham]

I used roller bearings with thrust washers top and bottom when I made my steel snake, but either one should work IMHO

[Jake Helmboldt]

The primary issue is getting a bearing that is designed for either, radial, or axial loads, or a combination bearing. Both roller and ball bearings can be used, but it has more to do with the races and their ability to withstand the load types.

I don't have a hollowing rig so I'm not sure, but axial loads would seem to be greater. In fact, it seems there is virtually no radial loading.

[curtis rosche]

i would say the one on the right. think about how the force will be on the rig, and the direction of the bearings you are using. if i assume correct. your bearings will be in the horizontal position they are in in the pictures. the load with be vertical/up and down from the force of the wood pulling the tool down. the bearing on the right should put the force on the pins, where as the one on the left will put the force on the race

[Bernie Weishapl]

Either one should work fine. I have seen both used on homemade units and both work fine.

[Alan Trout]

Dave

I just looked at my Monster and it just uses thrust bearings much like the ball bearing units you posted.

Good Luck

Alan

[Mike Svoma]

The primary issue is getting a bearing that is designed for either, radial, or axial loads, or a combination bearing. Both roller and ball bearings can be used, but it has more to do with the races and their ability to withstand the load types.

I don't have a hollowing rig so I'm not sure, but axial loads would seem to be greater. In fact, it seems there is virtually no radial loading.


I think Jake hit it right with a combination bearing. The load will actually be a torsional type load with the torque arm pivot being the tool rest, thus the need to handle both axial and radial loads at the same time.

Mike

[Dave Schell]

Thanks for all of the replies. I had bought some of the needle (roller) type bearings shown on the right above and gave them a try the other night. I believe the whole purpose of these bearings is to allow you to tighten the bolts in the joint as tight as possible to eliminate slop in the joint while still having a smooth moving joint. I noticed if I tightened the bolt too tight, I could completely negate the bearing and essential lock down the joint from moving at all. So I was wondering what some of the productions models use. I might try the ball bearing type to see if they make any difference. Seems like there is a fine line in tightening the bolts between a smooth moving joint and one that is either too tight or too loose.

[Rob Cunningham]

Thanks for all of the replies. I had bought some of the needle (roller) type bearings shown on the right above and gave them a try the other night. I believe the whole purpose of these bearings is to allow you to tighten the bolts in the joint as tight as possible to eliminate slop in the joint while still having a smooth moving joint. I noticed if I tightened the bolt too tight, I could completely negate the bearing and essential lock down the joint from moving at all. So I was wondering what some of the productions models use. I might try the ball bearing type to see if they make any difference. Seems like there is a fine line in tightening the bolts between a smooth moving joint and one that is either too tight or too loose.
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Yes, if you tighten the nut too much it will bind the bearing. It will happen with either type of bearing. I used lock nuts and stripper bolts on mine and tightened until I was happy with the movement. It helps if the parts are machined accurately, then the stripper bolts limit over tightening of the bearing.