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Author Topic: Questions about bearings  (Read 310 times)

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R.U. Sirius

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Questions about bearings
« on: October 25, 2021, 10:03:30 PM »

I've started refurbishing two Lortone arbors, and discovering along the way just how much I don't know about these kinds of mechanisms. I would really appreciate it if someone here could clarify these few basic questions!

The first arbor is Lortone NS-8. Insert bearings in rubber cushions are held directly in the cast aluminum body.  I found cheap replacement inserts that fit into cushions just fine, but they come with lubrication holes, whereas the original inserts were sealed. Is it a good idea to use lubricated inserts with these old rubber cushions? If so, do I periodically lubricate them by taking them out and placing them in a mount with grease nipples just to refill them with grease? If not a good idea, I will just shell out 2x$20 for a pair of new sealed bearings preinstalled in new rubber cushions.

The second arbor is Lortone NA-8. Bearings (again with rubber cushions) are in flanged aluminum housing with four holes. Is it possible to pull out and replace the bearing/cushion assembly without deforming the flimsy-looking housing?  Or should I be buying a complete replacement? Would this be acceptable - https://www.bearingscanada.com/mobile/product.aspx?ProductCode=kit7427&404 ?

Many thanks in advance for sharing your thoughts!
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lithicbeads

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Re: Questions about bearings
« Reply #1 on: October 26, 2021, 01:42:05 PM »

New lortone machines are not lasting bearings included. I have never been more disappointed with a machine as the lortone cabber I bought a few years ago.
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Slabbercabber

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Re: Questions about bearings
« Reply #2 on: October 27, 2021, 08:14:44 AM »

You really should have sealed bearings for anything used in lapidary.  As to the second, even having spent my life designing machinery, I've never encountered anything like those.
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catmandewe

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Re: Questions about bearings
« Reply #3 on: November 05, 2021, 08:03:15 PM »

That last bearing can be put inside the housing and tightened up, it is a concentric bearing which means that it has a locking collar which will center the shaft in the oblong hole in the bearing, it takes two oblong holes that need to align up to make one round hole.
Hope that makes sense to you.

Tony
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irockhound

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Re: Questions about bearings
« Reply #4 on: November 05, 2021, 09:48:49 PM »

I always hated the collet/bearing twist type.  I switched to the std dia hole with the matching collet with double set screws.  Just seemed more logical to me.
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R.U. Sirius

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Re: Questions about bearings
« Reply #5 on: November 06, 2021, 03:07:59 PM »

The eccentric collar type is supposedly better than two set screws, as it distributes stress more evenly around the shaft. Its just important to lock the collar by rotating it in the direction of rotation of the shaft (a hook spanner would be most appropriate), and tighten the set screw in that position.

Having said that, a pair of set screws should work just fine for lapidary purposes - relatively low speeds, and extremely low radial loads (we are actually bellow the minimum required bearing load according to SKF!).

Regarding my original questions, I found sealed 204-12 insert bearings at US$10 or so, and will go with that next time. And the flanged bearing mount on Lortone SA-8 and Beaver arbors is referred to as "bearing hat" in Lortone manuals, part number 063-008. I asked them about it, they referred me to Kingsley North, who told me they are "checking with the manufacturer" (presumably Lortone?)...

Flanged square or round bearing mounts with four holes are plentiful online, but without the rubber cushion! Also, the hole spacing doesn't match, so I would need to drill into the arbor housing. So, I'll wait and see what Kingsley North offers. If they come back empty-handed, I'll just try and preserve the existing "hats", or have something machined.
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