Arbor bearings....sadly one more time

My Jet cabinet saw was been unusually noisy lately. It has been making a loud fast knocking noise.
It became especially clear to me when i visited my Dad over thanksgiving an I noticed how much quieter his Delta contractor saw was.
Simple diagnostics yeilded nothing so I knew that I had to go about it the hard way... pull of the tables and wings and top.
With the belts off the arbor, turning it by hand I hear some some mild abrasive white noise thoughout the rotation, and a specific clunk at the same point in the rotation at each turn. I'm confident that this is the "knocking" that I head under power.
Here's the rub.... I just replaced the bearings about 6 months ago. Since the saw was only about 6 years old (just past warantee) I talked Jet into sending me a new set gratis.
I suppose it's possible that I got a bad bearing, but my lack of experience in this realm makes me fear mechanic's error.
Is it possible that some slight misalignment (belt pully?) or incorrect belt tensioning could fry a set of bearings?. This is a major PITA that I hoped that I would not have to address for a very long time.
Help!
Steve
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"C & S" wrote:

Proper installation of a ball bearing is critical to successful operation.
Biggest cause of premature failure of a BB is "brinelling" which happens when installation forces are transferred from the outer race thru the ball to the inner race, causing "minute dimples" to be formed in the raceways.
Not saying that is what happened, but it is a possibility.
You need to make sure you properly install the bearings without the possibility of brinelling.
Can not comment further without seeing a cross section of the shaft ass'y.
Lew
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Thanks Lew, I appreciate your insight. It does indeed make sense to me that they could have been damaged upon installation.That actually makes a whole lot more sense than run time damage.
Followup bearing question:
I don't know thing one about bearings. The JET part is BB-6203ZZ. Some searches suggest that JET/Powermatic/WMH tool group use this part in a wide variety of woodworking tools. It also appears that 6203ZZ is a generic precification:
http://www.vxb.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=kit1040&Store_Code ¾arings
http://store.eurtonelectric.com/6200series.aspx
Could it be that 6203ZZ is the entire specification that I need? From a quality standpoint, might these be interchangable with the Jet (EOM) part priced at roughly 3-5 times the price?
Thanks,
Steve
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"C & S" wrote:

http://www.vxb.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=kit1040&Store_Code ¾arings
Your bearing is a basic 203 (20mm or 0.669" bore) bearing which tells me you have a 5/8" (0.625) shaft.
The ZZ designation specifies the seal/shield configuration.
It is the standard ball bearing used in fractional HP motors, automotive auto alternators and auto tyrannies.
There are more 203 BB made than all the rest of the BB sizes put together, thus it is the lowest cost BB made.
Go to a bearing supply house and buy a pair of 203, double sealed BB and you are good to go.
Brand is unimportant, a 203 is a commodity item.
A piece of advice.
Don't try to install bearings without using an arbor press.
If you do, it is a disaster waiting to happen since it is almost impossible to install BB without brinelling them unless you follow correct installation procedures and use an arbor press.
Have fun.
Lew
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Correction:
Late at night, brain not completely engaged.
203 BB has 17mm bore, not 20mm as shown below.
0.669" is correct.
Lew

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I'm so muchly obliged. That's great info.
Now I just have to pigure out where in a small rural community I can some soemone with an arbor press.
Thanks again.
Steve

http://www.vxb.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=kit1040&Store_Code ¾arings
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"C & S" wrote:

My bet is some of the local farmers have a shop equipped with an arbor press.
When you start shelling out $150K-$300K for a tractor and/or other pieces of farm equipment, you probably have a shop to maintain that equipment.
Do you have an automotive machine shop in your area?
Lew
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Nah, just some old sockets you can hammer on, pieces of pipe, etc., brass square stock maybe at best. Find one thats slightly smaller than the outer race and grab the three pound sledge. If that dont work just get some emery paper and sand the shaft/gland a bit till it pounds in there. My favorite farmer/mechanic line is "it will wear in". Lot of big tractors around here and I have yet to see to many shops (even the tractor dealers) with what I would think of as "a shop".
Yuk yuk, ;)
Mark
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Keep us informed.
I have a Jet cabinet saw that is supposedly about a year old. I bought it used. It's appears in like new condition.
However, when I grap ahold of the blade/arbor, I can feel a few thousands wobble. I could not feel similar in my 10 year old Delta contractors saw.
I've not yet removed the belts (how do I do that? Is it easy to put back?)
I was thinking if there is ~any~ detectable wobble that is not good.

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That does not seem right... but the proof is in the pudding. Can you get a smooth cut cut with a quality blade?

back?)
It's pretty simple if you have the top off.... but then you can count on doing a full tuneup (alignment). But if you are considering changing bearings, you're there already.
It could probably be done from the underside, but it would awkward to say the least.

If you like, I can take some interior pictures while it's open/diassembled .... just email my sawdust address directly.
Regards
Steve

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I have heard this noise come from a loose pulley also. Not loose to feel or by sight, but loosening the pully set screws and insuring that they are on top of the key and retightening solved the problem.
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Yep.. had that experience with my jet 1442VS lathe..
I was sure that the spindle bearings were shot, but decided to try a tuneup first..
The bottom pulley was slightly off of the indentation for the set screw and the leading edge of the key showed rounding.. Replaced the key and set screw and the noise went away..
mac
Please remove splinters before emailing
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Ding ding ding! we have a winner.
Mac, I owe you an adult beverage.
The set screws were loose on the pully and that was causing the "clunk". I must admit that I don't understand the geometry the rattle as I would expect belt tension would hold the pully to one side of a sloppy keyway but tightening it made the noise go away.
It's all back together and I did not have to pull apart the arbor assembly which is the dicey part due to lack of proper tooling.
I learned a little bit about bearings and I'm getting more confident and efficient about breaking down the saw and getting it back together and aligned. So, it's all good. The beast was only "down" for a day and a half. with about 3 hours of break down setup and alignment.
Thanks all,
Steve
wrote:

or
on
tuneup
and the

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wrote:
That's really cool, Steve... And a lot of what these groups are all about..
I didn't think that the pulley/key could have caused the noise on the lathe, just something I noticed when I pulled it apart and figured that I might as well fix it.. I was amazed when the "bearing" noise went away... kept waiting for it to come back, but hasn't in a LOT of hours on the lathe..

mac
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This usenet group still seems to work, which is why I hang out and have left other groups. I suspect it's because there are a lot of FOG's in here who like the simplicity of the format of usenet (like I do).
I can't tell you how many times I've torn something apart to fix, what I though was a problem, only to have it be something else.... most often, a much more simple fix. In the long run, though, I'm thankful for that inquisitive spirit in me that causes me to "crack the box" and look inside because I always end up learning a lot in the process.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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"C & S" wrote:

Glad to see it was a simple solution.
Hint:
Now would be a good time for an application of some LocTite<grin>
Lew
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I think it's also a time to remind ourselves that periodic checking and maintenance can save a lot of stress and money in the long run..
mac
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Call these folks and get some decent replacements not made in a garage in India.
http://www.accuratebearing.com /
C & S wrote:

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On Tue, 09 Dec 2008 21:03:44 GMT, Pat Barber

Insist on NTN - highest quality, quietest running. Known throughout the electric motor industry.
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