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PM3520 bearings...need ideas

E

Ed_McDonnell

Joined
Jul 18, 2006
Messages
643
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2
Location
Central Florida
I turn a lot of really wet stuff and after 5 years of really hard use the outermost bearing on my powermatic 3520b headstock needs replacing.

It took less than 10 minutes to pull out the spindle. With the spindle in hand I thought to myself "This is way easier than I expected it to be". Turning the bearings I can hear a grinding clicking noise in the front (unsealed) bearing, confirming my belief that the bearing needed replacing.

So there I am with the spindle in hand. Two bearings on the shaft separated by a loose fitting bushing / spacer. The bearings must be a press fit because I can't get them to budge. I don't see any rust or dirt that might be causing them to bind on the shaft. Because of the shape of the spindle, I can't press them off the spindle shaft.

I would welcome all ideas on how I might get these bearings off the spindle. Preferably without destroying the spindle or bearings.

Ed
 
Ed,
Don't mess around with them. Buy the new bearings, sealed if possible, and bring them to a machine shop to be pressed off and the new ones pressed on.
Remember, you have quite a long guarantee on the 3520B. Have you called PM to seek advice? They are really helpful.
faust
 
Faust M. Ruggiero said:
Ed,
Don't mess around with them. Buy the new bearings, sealed if possible, and bring them to a machine shop to be pressed off and the new ones pressed on.
Remember, you have quite a long guarantee on the 3520B. Have you called PM to seek advice? They are really helpful.
faust
Click to expand...

Hi Faust - Sadly, my warranty ran out last month. I did try calling PM. PM does not seem to be the same company they used to be. In the past a call to PM tech support was quickly answered by knowledgeable helpful techs. It's been over a year since I last spoke to tech support at PM. Here's how my calls went today:

Call #1
Dial
Listen to recorded message telling me to hold the line.
Listen to silence for a while.
Listen to recorded message telling me they are sorry about the wait.
Listen to silence for 10 minutes.
Listen to somebody pick up the line, rustle some papers and then hang up on me.

Ok...maybe they dropped the phone as they were picking it up....it happens. Try again.

Call #2
Dial
Listen to recorded message telling me to hold the line.
Listen to silence for a while.
Listen to recorded message telling me they are sorry about the wait.
Listen to silence for 8 minutes.
Woman answers and asks how she can help.
I ask for PM tech support.
She says just a moment and she'll connect me.
Listen to on hold music/commercials for 15 minutes.
Get pissed off, hang up and decide that my next lathe, when the time comes, will not be a powermatic.

I've got the replacement bearings. Trying to find a shop to do the replacement without ruining the spindle is an option. I don't know any shops that I trust though. I would have to do a lot of research.

Thanks for the reply.

Ed
 
Ed, where did you buy your bearings????
local or mail order?
 
Ed,
After about 5 years with my old 3520A, I had the same problem. I went to a local bearing supply place (Kaman), ordered the bearings, took them to my favorite tool repair guy, along with the headstock, got it repaired for cheaper than I could get the bearings from PM/Jet/WMG Group, or what ever they are called. The tool repair place told me that they had a bear of a time getting the old bearings off because they had rusted into place.

robo hippy
 
Hi Charlie - I got the two front bearings at enco (6207zz). I went to ebay for the single back (handwheel side) bearing (6206vv). I might have been able to get by with a 6206zz or 2rs from enco for the back, but I don't know enough about bearings to know if using double shielded (zz) or double sealed (2rs) instead of double non-contact sealed (vv) would have created problems.

The total cost for all 3 bearings was less than the price of one bearing from PM.

There are a bunch of skate places that sell bearings online and they charge even less. They might be selling the same quality bearings, but they might not. I didn't want to spend the time investigating to maybe just save another $5 or $10.

I've used enco bearings to in other tools and have had good results. I went with what I was comfortable with.

Ed
 
Thanks Robo Hippy. That's two votes for "take it to a pro" to get the bearings off the spindle. The good news is that it was really easy to get the spindle out of the lathe and I don't have to carry the whole headstock somewhere if I got the "let a pro do it" approach.

If I knew a pro I would definitely go this way. I don't, so I'm kind of hoping that somebody will know a way to get them off without having to spend a fortune on special tools.

Ed
 
I would think any good machine shop could do it, or at least send you to some one who could do it.

robo hippy
 
Any place that has a press and knows what they are doing can get the bearings off. I'm still new at it. I purchased a hydraulic press a year or so ago because I needed a Hydraulic jack and the only place that had one only had it in the press. I had bee wanting one and bought it. since then I've pressed a few bearings on and off for people but haven't done a Powermatic yet. sometimes I think it takes special adaptors to safely put the new bearings on without damaging them.
They probably do have rust. I spray a good penetrant on for several days before I try to remove anything. In the past I was able to get them off with a mallet and wooden block after giving the penetrant a chance to work.
To install the new ones I put the shaft in the freezer and the bearings in the sun. I was able to tap them on with custom made wooden adaptors that sit on the inner race. Now I would use the press instead.
 
For one thing you can take any bearing or seal to a bearing/machinery shop and they can measure it with a micrometer, and usually match it up with something easy to get. Metric or standard, does not matter. The main reason that those bearings come off the spindle so hard is that they are heated (they expand), and after putting them on the shaft they contract and set up tight. you can press them off, I do recomend taking them someplace that has a bearing heater to have them put back on. Another trick is to put the spindle in dry ice and is will shrink enough to get the bearing on. Just make sure that if the old bearing leaves any scarring, or burrs on the shaft to take a file or emery cloth and smooth it out or the bearing will get halfway on, and stick, and your expansion/contraction will occur, and you have just wasted a bearing. Under no circumstances do you want to hammer a bearing into place, and if you should ever drop it on a hard surface it is ruined. I have replaced bearings from 1/4" diameter to 60" in diameter, and these are just some rules that I follow. I hope this helps you out.
 
If you got the replacement bearings really cheap then you probably got what you paid for -- certainly not more. The numbers that you mentioned only describe the size, but there are several other parameters that may also be important. For instance, with a lathe where there is often an axial load on the bearing, deep groove bearings are preferable to standard groove for axial loads. Also, the fit between balls and inner and outer races can range from loose (most common and lowest cost) to preloaded with no free play. Bearings also have a maximum rated speed and for cheap ones, the speed may not be as fast as the maximum spindle speed.

I will echo the recommendation to take the spindle to a machine shop. While you may have concerns about the capability of a shop, this is the type of stuff that they do every day. You are thinking of doing the job yourself without the right tools and no prior experience -- is that better or worse than taking it to a machine shop?

Bearing replacement is something that I do not want to do very often, so I don't mind paying for better quality bearings and also having the job done well. It is too easy to ruin a spindle -- and I am sure that they are not cheap.
 
I agree that you get what you pay for. Don't buy a cheap bearing. But, if you take it and have it matched by an industrial bearing shop (someplace whose main business is heavy industry) You should get top of the line. Like Npk or smething. Something made for a long, dirty, abusive service life.
 
My bearing guy matched the numbers to others in his catalog. He said that the ones used were very high quality, and he was able to get the same ones. Don't take short cuts on bearings, agreed!

robo hippy
 
what type of bearings did you get?
 
Hi John - So there I am, standing in my hot sweaty shop (aka the garage) with the spindle in my hand. I'm staring at it and using the full force of my mind and all my will to try and mentally get the bearings to fall off the spindle when a car pulls up in the driveway. It's a guy I see every now and then, usually when he wants me to donate a bowl to a worthy charity. As I go looking for a nice bowl, he sees the spindle and a couple boxes of bearings laying on the workbench. He puts 2 and 2 together and says "You aren't going to try and replace those bearings yourself are you?"

I sheepishly answer "....noooooo......".

He leaves with the bowl, the spindle and the bearings. An hour later he's back with the bearings replaced. Took about 10 minutes to get the lathe back togehter and another 5 minutes tinkering with the pulleys to get the belt running perfect and it was good to go.

I think it runs better now than when it was new.

Ed
 
charlie knighton said:
what type of bearings did you get?
Click to expand...

Hi Charlie - The bearings powermatic used were:

FAG 6207.2ZR.C3 (double shielded) and a FAG 6207.C3 (open) on the right hand side (with the open bearing closest to the work which makes no sense to me. This is the bearing that failed.).

KBC 6206DD C3G81 (double sealed) on the left side.

FAG and KBC are korean bearings made by Shaeffler Korea Corp.

Lots of information available at kbcbearings.com

Also found the following site useful:

http://www.gizmology.net/bearings.htm

My bearings were replaced with what powermatic used, except the open bearing was replaced with another double shielded bearing.

Ed
 
Ed, that is a great story- help when needed. You might turn the guy a nice bowl as his payment.
 
Hi Ed, I grew up south of Miami, and as a motorcyclist riding British bikes, any machine work that needed doing was taken to a specialty machine shop that only worked on bikes. Their knowledge base was extraordinary, and one of the shops that I used was run by a former Navy machinist from a submarine tender. He really knew his stuff! It's been awhile since I lived there, but ask around and you will be pointed in the right direction. When I restored my Yates-American J-170 wood lathe, I purchased double sealed bearings from a local supplier here in Daytona Beach, and he pointed me to a machine shop just a mile away, and the guy did a super job.

Smiles,
Rick
 
Ed, any competent machine shop or auto repair facility can easily press your bearings..they do that type of work all day long, esp. front wheel drive autos. An appropriate press-plate is used to remove the bearings, then the old bearings can be used to install the new bearings. The wrong procedure will ruin the new bearings immediately...as the new bearing is being pressed on, it should be able to be rotated easily at any time. If it won't rotate with even the slightest pressure applied, something is wrong. Generally, the new bearings should be pressed onto the shaft using pressure against the inner race, not the outer shell....pressing against the outer shell will tend to blow the bearing apart.
 
Ed_McDonnell said:
Hi John - So there I am, standing in my hot sweaty shop (aka the garage) with the spindle in my hand. I'm staring at it and using the full force of my mind and all my will to try and mentally get the bearings to fall off the spindle when a car pulls up in the driveway. It's a guy I see every now and then, usually when he wants me to donate a bowl to a worthy charity. As I go looking for a nice bowl, he sees the spindle and a couple boxes of bearings laying on the workbench. He puts 2 and 2 together and says "You aren't going to try and replace those bearings yourself are you?" ........
Click to expand...

That had to be Divine Providence. 🙂

You owe your friend the best bowl that you can make -- or one for him and one for every charitable event.
 
after reading Ed's post and following thread, i took my headstock to machine shop and they changed out bearings on 1642. they said the front bearing was ok but the back one was shaky. i wonder if i have been putting too much pressure with the tail stock for the back bearings to be needing changing? i do some multi-axis work.......the back bearings are much smaller than the front...... i wonder if that affected the wear.......

good time for shop downtime is when it is hot
 
Last edited:
I have seen a lot of woodturners really crank down on the tailstock pressure. Most bearings are not designed to withstand that sort of abuse. Most ball bearing assemblies are intended primarily for pure torque loads (which hardly ever exist in the real world), but they can also withstand a reasonable radial load (that is, perpendicular to the spin axis). They can also handle a small axial load ( that is, in the direction of the spin axis which is what occurs when applying pressure from the tailstock). However, normal ball bearings are not intended to support large axial loads. Axial loads tend to brinell the races (that is, the races become dimpled by the pressure from the balls).
 
I had similar bearing problems with my PM4224 while it was under waranty. The bearings had been replaced three times, yes three times, and I still had a rumble and a heat problem in the head shaft. All the people I spoke with at PM Technical were extremely understanding and did everything they could to solve my problem. I can't say enough about how hard they tried.

Finally, and get this all you people who may be considering PM, or some other brand for that matter, I spoke to the lady in charge of customer service/satisfaction, etc., at PM, and, boy, was I ever ready to give her a full load of my dissatisfaction with PM. Before I could, she said "Mr. Roller, we do not want that lathe out there in in the field. We are sending you a new PM4224, and, moreover, we will send someone out to set it up an pick up the defective lathe."

I had a new lathe within two weeks. All I had to do was unlock the shop door.

Finally, to the cause of the problem. Whenever the headstock is milled, there can be absolutely no movement of the stock. If there is, the alignment from one end to the other of the headstock can be out of alignment with the bed of the lathe. This will cause bearing problems.
 
I had a broken garage door a year or so ago and decided that if I had a good Hydraulic jack I could push the door parts back together and rivet them with an additional bar and it would solve the problem. I went looking for a cheap jack and my local tool shop that apparently buys tools from the same people Harbour Freight gets theirs only had a jack in a press.
Well heck I've been wanting a press for a long time so I bought it. I've changed a couple of bearings on things now and man is that sweet. I have learned you can screw it up if the press is not aligned with bearing properly.
So there is a learning curve and if you plan to do this only once going to a machinist is the way to do it. I've been there before. Now with a metal lathe to make the proper mandrel and the hydraulic press I can probably replace my own. I have done it on smaller lathes but not tried it on the larger ones yet.
 
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