Question on electric motor bearings

J

John TV

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So still consider myself as green as grass to this whole hobby and there are all kinds of new experiences I have never tried before.

I have a 5 hp. 3 phase motor that is the "idler" motor for my rotary phase converter. It was used when I put it into service and it is a Baldor "drip proof" type motor. I have used it very little and I am getting what I first thought was a harmonic high pitched whine (very anoying) after the motor runs for a minute or two. I now wonder if the bearings are starting to go since a pump of grease will make the sound go away for a while. I have just started to research the replacement of the bearings and here is where my question comes in. I have never ordered or repaced bearings before on anything other than a car or trailer. In my initial look up of the likely size, I am seeing a wide range of types, etc. Is there a thread here I have missed that is a primer on bearing info? Looks like I can spend between $10 and $240 per bearing? Needing some guidance on what level and supplier to use. I most likely will call Baldor and get their parts but it would be nice to have some knowledge before I make a decision. Thanks for your thoughts.

John in Minnesota
 
Just pull it apart and gm isit a local bearing supplier.

A 10 ish dollar part


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Hi John,
bearings for modern electric motors are most likely measured in millimeters.
ABEC3 is a grade suitable for electric motor use in most instances, this being one of them
your 5 hp motor may have 6305ZZ bearings.
i would suggest using neoprene sealed bearings, as the seals generally make the bearing last longer
if your motor does in fact have 6305 bearings, the designating would be ABEC3 6305SS

here is a chart of bearing sizes
https://www.bearingworks.com/bearing-sizes/

SKF is a good name that's great quality
 
Good input from Ulma Doctor. Sometimes SS (for double sealed, sealed on both faces of the bearing) in the bearing part number is changed to -2RS, which means the same thing as SS. The double sealed bearings work much better than double shielded (ZZ) at keeping dirt and grit out. In the old days when bearings were sealed with natural rubber, they would disintegrate at a young age, so double shielded became popular. Now, the seals will usually outlast the bearings, so they are the way to go until you get into really high speeds, then the lack of rubbing contact in the double shielded bearings might be more useful, the seals might overheat if they were used. ABEC3 bearings are appropriate for an A/C electric motor.
 
As with most every thing these days I believe quality goes with price and the high price bearings are for use in high precision machines.
If you can get the bearing races out of the motor most bearing houses can identify them and cross reference them to different manufactures and perhaps price range. I did this with a drill press with good results.
Have a good day
Ray
 
Great info from you all. Now just need to find the time to pull the motor apart. This forum is so great at sharing and helping us new to the hobby. With the info I have learned here, I am much more confident in attempting to undertake new challenges. You tube is awesome too but here you get different opinions and options and the logic behind the options. You folks are fantastic, thank you.

John. Minnesota.


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Most regreaseable motor bearings have plugs on top & bottom. The proper procedure is to remove both plugs, pump grease into top port toll it flushes out the old grease from the bottom. close ports. Forcing grease into one port only will not grease bearing, but force grease into the motor housing. Just the way I was taught during my 35 years as a maintenance supervisor.
 
Wow, had no idea, thank you. I will look for those bottom ports. Top is just grease zerk. Makes sense, just never used anything other than automotive greasing before. I love this forum!

John


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not all motors have grease ports or grease plugs to remove,
most NEMA motors i work with don't have grease ports with removable plugs, just zerk fittings
 
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