electric motor bearings?

I'm rebuilding a 7.5 hp electric motor. Its shaft end bearing had a metal seal away from the shaft end and was open on the other side. The other
bearing also had one metal seal and was open on one side. The motor has zerk fittings for greasing.
I'm going to use this motor for an RPC idler motor only. I'd like it to run as quietly as possible. In calling bearing houses, two different clerks told me that electric motors often have two metal seals i.e. ZZ.
Should I use ZZ, 2RS, one side metal, or open? Why?
Thanks,
GWE
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My opinion is that the bearings' contribution to noise will ne minimal. Motor fan and windings hum will contribute more. I would go with ZZ just so that I am not bothered with oiling, dust etc.
i

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You would think so, but my experience proved otherwise.
I bought one of those ubiquitous $200 bandsaws from a local salvage-oriented retailer.
Even though it was brand new, it had, obviously, been underwater at some point.....perhaps in the ship's hold?
When you hit the switch, the noise it made was a cross between a klaxon and a siren. My neighbors all knew when I was cutting metal.
As a part of my "Neighborhood Relations Policy", I would close the shop doors if I had to cut something with that saw while working in the evening.
Since the machine worked fine, I tolerated the noise - hoping that the shop phone would not ring while I was using it....since I couldn't hear the phone ring, nor could I talk on it while the saw was running.
One day, I got fed up. I opened the motor up, took the bearings out, cleaned them up, and packed them with a good quality (military surplus) wheel bearing grease. They quieted substantially.
I took the bearing numbers, went to my local NAPA Auto Parts store, and found the exact replacements (alternator bearings) in-stock......sitting on the shelf......for less than $10.00 each.
I replaced them and the saw quieted so much, my neighbor from across the street asked if I had bought a new saw.
Again, that was my own, personal, somewhat surprising experience.....YMMV!
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The key here is "it had, obviously, been underwater at some point".

Yes, you put in new bearings, and the noise went down. That's what Grant wants to do as well, put in new bearings. I just do not think that the type of bearings will make much difference, noise wise.
i
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@NOSPAM.13850.invalid says...

"Electric motor quality" bearings are bearings that have either been manufactured or selected for quiet running.
http://www.dynaroll.com/catalog/pag027.htm http://www.vncbearing.com/tdata.html
Ned Simmons
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Get the double shields, you don't want or need sealed brearings.

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Grant Erwin wrote:

It depends on how you are going to use the motor, what type of enviorment it is going to be in. For your application a sealed bearing will work fine unless you are running it in a very dusty envoirment. Then an open bearing with a zerk fitting to flush the bearing grease and inject new grease is desired. There should be a pipe plug that you remove opposite the zerk fitting so the old grease comes out rather than pushing its way out along the shaft and creating a mess.
John
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Grant Erwin wrote:

Use a 2RS sealed pregreased bearing.
John
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Grant Erwin wrote:

Z is better for dirty environments. I guess you want a Z, because there must be some way to get the grease in. ZZ and 2RS are greased out of the factory, so you could use them and ignore the zerk fitting. If you only get a ZZ and need a Z, you can pry one sealing out with a screwdriver.
Nick
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On Tue, 10 Apr 2007 16:58:46 -0700, Grant Erwin

If you have a metal seal it is most likely a shield. If you buy a sealed or shielded bearing it is greased for life - the grease should outlive the metal and relube is not required. Over 98% of bearings never reach their design life and most fail due to over lubrication so I would suggest that if you have a normal environment go with ZZ since they are cheaper than sealed. If you are in a fairly dirty environment, I would suggest going with NTN bearings with LLB non contact seals. I would not suggest going with 2RS as these are contact seals and create friction (drag and heat) and probably aren't necessary. If you want to go with a single shield and relube, I would suggest you reverse the bearing - put the shield on the lube side so it will act as a meter. It will actually do a better job of keeping the grease out of the windings than the way it was originally installed.
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Grant Last month I did the same bearing replacement on a 7 1/2 HP motor for my phase converter. As others have said, the difference in seals/ shields is minimal in this application.
I found bearings on ebay at 1/3 the cost from the bearing houses.
John Normile
On Tue, 10 Apr 2007 16:58:46 -0700, Grant Erwin

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Grant Erwin writes:

Dunno about that, but ...
Here's some old notes of mine on bearing nomenclature:
NTN (ntnamerica.com) (and others) bearing numbering system: (See http://www.us.nsk.com/page.asp?ID%5 for more code interchange info) Z = shielded one side, ZZ = both sides; ZS/ZZS = removeable, V/VV non- contact steel shields, D/DD contact steel, TS/TTS Teflon. L = sealed one side, LL = both sides. LB = non-contact sealed one side, LLB = both sides. LU = contact sealed one side, LLU = both sides. Suffix N = snap ring groove in outer surface of outer ring, NR = same with ring supplied. FL/FR = flanged outer ring, R = standard, RW/FRW extended/flanged inner ring. K = 1/12 bore taper on ID. Ball retainer cages: J = pressed steel aka "ribbon" (assumed if omitted), T2 = nylon, T12 = "plastic", G1 = machined, W = crown, brass cage for cylindrical roller bearings or L1 = other bearings, F3 = machined leaded steel, F5 = machined Cr-Mo steel, T1 = machined phenolic. D = OD, d = ID or bore, B = width, r = bore chamfer. SRDG = single row deep groove radial bearing, numbers 6xxx. SRDG cartridge (wider for more grease) = 63xxx. SRDG max capacity (extra balls via filling slot) = BLxxx. SRDG heat-treated high-strength long-life = TMBxxx. Felt seal = 8xxx, Wide-cup felt seal = WC8xxx. Angular contact = 7xxx, suffix G = flush ground for duplex pairing to elminate end play, suffix (?) C = 15 deg contact, D = 45 deg contact, none standard 30 deg contact. Duplex pairing: back-to-back (higher rigidity) = DB suffix, face-to-face (more misalignment tolerance) = DF suffix, tandem (added thrust in one direction) = DT suffix. Preload designations for precision pairs (using slight gaps in ring dimensions): N = normal, L = light, M medium, H = heavy. Double-row angular contact = 3xxx (extra balls via filling slot) or     5xxx (normal balls). Double-row self-aligning angular contact (spherical inside of outer ring) = 1xxx or 2xxx. Single direction thrust ball bearings = 51xxx, double direction = 52xxx. Double direction angular contact thrust ball bearings = 562xxx. Steel hardness in bearings typically 60 to 64 Rockwell C. Radial internal clearance = C2 (best), standard (C or no suffix), C3, C4, C5 (worst). Last three digits of number XYY: YY=ID: 00mm 01mm 02mm 03mm X=OD: code for size depends on ID. For ID 9mm or less, 3rd digit is ID in mm.
Bearing tolerance classification equivalents:
    ABEC    ISO    DIN
    ABEC 1    Normal    P0     ABEC 3    Class 6    P6     ABEC 5    Class 5    P5     ABEC 7    Class 4    P4     ABEC 9    Class 2    P2
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Richard J Kinch wrote: ( lot of good info) When I save this it writes as a .eml extension. Is there some way to convert this to a .txt file ? Anybody??? Thanx ...lew...
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On Sat, 14 Apr 2007 16:42:46 GMT, Lew Hartswick

Copy and paste to word processor - works every time.
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On Sat, 14 Apr 2007 16:42:46 GMT, with neither quill nor qualm, Lew

Ctrl-A, Ctrl-C to grab all the text, Start/All Programs/Accessories/Notepad to open Notepad, Ctrl-V to drop the saved text. In the Notepad menu: File/Save As, name it whatever.txt. Done.
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Rename. .eml to txt did you try that ?
I do some saving but often through a text editor. But directly has been done.
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Larry Jaques wrote:

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Martin H. Eastburn wrote:

Yea . Tried it but it puts a lot of extraenious junk in.
I'll try the copy and paste bit. Thanks. ...lew...
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