PM66 One Belt Vibrates

[Jeffrey Kibler]

So my 8 year old powermatic 66 starting acting a little funny last month. A blade that used to make a mirror finish (absolutely zero blade marks) started leaving blade marks so I started with the obvious and got the blade sharpened. Got it back and it did the same thing, so I sent it to a better sharpening place with CNC machines and computer balancers and it still did the same thing when I got it back. That I went full blow crazy and basically overhauled the saw. I took it completely apart, replaced the arbor bearings, cleaned everything spotless, and put link belts on it.... still does the same thing.

I do notice a harmonic vibration with the saw running and I'm almost positive that is what is causing the blade to shake just a tiny bit. All of my blades do it so I know the blade isn't the problem. I have also noticed that the belt closest to the arbor visibly vibrates while the saw is running and the outter one is rock solid. I'm almost positive the pullys are lines up properly so this makes no sense to me.

I'm open to any suggestions. The saw used to cut flawlessly so this is really frustrating me. Now I just can't let it go. I'm really suprised the v-belts (power twist by fenner drives) are acting like they are.

PS... i'm new to sawmill creek and I love it. What a great community of people.

[John McClanahan]

I run with only 1 belt for that reason. I don't do heavy duty sawing, so the single belt hasn't been a problem.

John

[Chris Rosenberger]

Have you run the motor without the belts to the arbor to see if it has the same vibration?

[Bill Geibe]

When you run multiple belts like that, if they aren't absolutely, identically the same length one will get the shakes. I have a Unisaw with three belts. When I rebuilt the saw I put three premium Gates belts on it. Two flopped around noticeably and the saw vibrated, especially on coast-down. With Unisaws, the trick is to get three matched belts from Delta that are cut from the same batch with sequential numbers. That cured the problem.

All that being said, I'd be surprised if one belt being slightly loose is causing a cutting problem. My initial thought was loose arbor bearings but you took care of that.

Bill

[Jeffrey Kibler]

I'm actually worried that I should have just bought the pre-fabricated arbor assembly from powermatic instead of just replacing the bearings myself. Either way I'm going to go take one of the belts off and see what happens. I think 99% of the people out there would be more than happy with the quality of the cut, however I know what the saw is capable of and I'm having a hard time living with this problem. I used to be able to rip or crosscut 3/4" boards with this blade and then finish them with no sanding at all. I'll do some troubleshooting today and maybe post a quick video. Just in case anyone doesn't believe me here are some pics of the "overhaul" i did on the saw. I literally ripped it apart.
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[John Lanciani]

Ditch the link belts and get a matched pair of the correct 3VX belts. Link belts are a problem solver for sure but they are a solution for problems that a PM66 does not have.

[Jeffrey Kibler]

Interesting. The reality is there is probably nothing wrong with the original belts. Maybe I'll toss one or two on there and try it when I'm playing around later.

[Randy Henry]

Went through the same thing as you did, except the reason I had to tear my 66 down was, the blade raise shaft locked up. Ended up doing a complete overhaul also. I noticed when I was taking mine apart, the pulley on the arbor shaft was not in line with the motor pulley, not even close, about 1/4" off. When I put it all back together, I moved the pulley in on the arbor shaft to where it was perfectly in-line with the motor pulley. The saw runs better than it ever has. It now makes the "mirror cuts" like you said. I used the same belts that were on it though.

[David Kumm]

Link belts are a poor choice for multiples as they never are exactly the same even if you count the links. Optibelts are manufactured to match without having to look for the same lot. Multiple belts have been largely replaced with single VX belts in newer machines. Dave

[Jeffrey Kibler]

So i'm pretty torqued right now. I took the belts off and started the motor and the exact vibration i was talking about was there. I knew immediately what that meant... so i started digging. Took off the big 5HP Baldor motor slowly spun the shaft and i could hear the pully side bearing grinding away. Took the motor apart, took the rotor out and spun the bearing and it was completely shot. I don't know if this was enough vibration to cause the blade marks i'm seeing but I guess we will find out when i get some new bearings installed.

The reason I'm kind of upset is that this motor was extremely expensive and it is designed to never get a drop of saw dust in it. Mine had plenty of very fine saw dust in it. I asked powermatic about a year after i got the saw if i should be greasing the motor periodically and they told me absolutely not. Fast forward 6 years I call them again when i start having these cut quality issues and ask them the same question.... they again say no. Now that i have the motor apart i'm positive they are wrong. The grease plugs on these motors are not for greasing the bearings... they are actualy designed to create a seal between the motor casing and the bearing making it so the motor is essentially sealed. When i pulled my motor apart there was only about 30 degrees of the 360degree cavity that had the grease seal still there. I'll be calling Baldor on Monday to see what they say, and if they say i should have been greasing the motor I think powermatic is going to be buying me some bearings.

I'm wondering if anyone else has had bearing problems with the baldor motors. I think i'm going to poke around and see what i find. Attached is a low quality video. If you listen close you can hear the bearing grind away. You can actually move it axially and radially.


http://www.youtube.com/watch?v=hngX-BrTNGQ&feature=youtu.be

[Don Jarvie]

Replace the motor bearing with some sealed bearings and it should be ok. The bearing may have been bad and it took all these years for it to go kaput. Replacing the motor bearings is easy enough since you have done the arbor bearings already.

[Chris Rosenberger]

Glad you found the problem. It looks like the bearings were sealed, so greasing the motor would not have helped.
Most dust gets into motors through the electrical boxes. When you put it back together, seal around the electrical boxes & power cord with clear silicone caulking.

[David Kumm]

It's not all that unusual for motor bearings to fail. they deal with some heat. Look at the code on the bearing as they should be spec'd as a motor bearing which are a little looser- I believe- to compensate. Dave

[Lee Schierer]

I'm really suprised the v-belts (power twist by fenner drives) are acting like they are.

PS... i'm new to sawmill creek and I love it. What a great community of people.

No matter what price you pay for link belts, they are not suited for use on machines with more than one belt running in tandem. The slight differences in length will make one belt work harder than the one next to it. Get a pair of matched belts and your problem should go away.

[Peter Quinn]

Glad you found the problem, I have the same saw, no motor issues to date. I'd get a matched set of VX belts, leave the link belts for the craftsman saws or keep them for a rainy day when some odd belt you can get brake and you need to keep working. I don't see those as a real solution, particularly on multi pulley machines.

[Jeffrey Kibler]

Not sure if I found the problem causing my cut issues but I surely found a problem. I'm going to track down some bearings tomorrow and see what happens. Wish I had a bearing press.

[Jeffrey Kibler]

Well I replaced the bearings on my motor and no dice. It was a good excuse to finally get a 20ton shop press though. The one bearing was definitely bad so I'm not upset about changing them out and cleaning up the motor.

So once the saw was all back together i tried a few things. I'll see if anyone can decode this information and in some way make it useful.

1. With the motor back on the saw I started it and could still hear a very slight vibration. When I say very slight I can still balance a penny or a dime on the top with the saw running and it doesn't budge. With the motor running I chaged the hight of the arbor and it definitely changed the sound of the saw/vibration. Then i noticed when I tightened down on the height adjust lock knob the noise got significantly louder. I don't understand when this knob would have any affect but it did.

2. I put the old belts back on the saw and fired it up. Noise/vibration was no different but i still saw the same noise increase when locked down the height adjust. I also noticed changing the angle of the blade changed the sound.

3. Put a couple different blades on and got pretty much the same cut quality as before. What is weird is that i put the forrest WWII on the saw and it actually cut better than it ever has, but when i put the 80T freud on the cut was not impressive (like it used to be).

4. Measured voltages from all terminal points in the starter (on/off switch) and everything looked perfect.

I don't know if this information means anything to anyone. I'm pretty tempted to go out and buy a new 80T blade and see what happens. Maybe I'm just chasing my tail here. Just torques me that the saw used to cut flawless and now it doesn't anymore.

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[Jim Neeley]

Jeffrey,

Have you tried picking up a matched set of belts, as suggested earlier? These aren't just two new belts, purchased at the same time from the same place, they are sold as a set. The factory warrants they are to acceptable specs.

If one belt stretches a tiny bit more than the other over time, one belt must slip with each turn which can introduce cyclic stresses. I'm a fan of link-belts but they aren't a good fit for multi-belt systems. If you had them work good for a while, good for you. That doesn't mean they won't become a problem.

I may have missed the post where you did this. If I did, I apologize in advance.

Jim in Alaska

[Jeffrey Kibler]

I haven't gotten a new set of belts but I did take the link belts off and put the original matched set back on. Vibration is there with no belts on the saw though so I'm thinking the belts aren't the issue. That or I have more than one issue.

[michael case]

Jeffrey,

I had a powematic 66 of about your vintage . Brand new right out of the box it gave crap cuts no matter what blade I used. I had the bearing and arbor replaced and the same unacceptable run out was still there. I just figured it was due to play in the bearing arm. There were a lot of other issues with my 66 and I was glad to see it go. But, yours actually worked right for years! And its still doesn't work right after all you did - Wow that's weird! I guess the suggestion about the matched belts would be worth a try. It would just crazy if that's all it is. Maybe my belts were bad or misaligned? I'll never know now. The only other things I can think of besides the belts is that maybe the arbor bearing is seated a wee bit off or perhaps the bearing arm has developed some play around the pivot shaft - or perhaps the nuts on the shaft are loose? Anyway, I sure hope it works out for you.

[Jeffrey Kibler]

That is the other weird thing.... the runout on my saw arbor right now is zero... like .0000 the dial indicator doesn't move. So something is going on with the saw running, and with this vibration present without the belts i don't think it's that. I put on a brand new freud glue line rip i bought like a month ago and the cut looked worse than a cheap 20T i used to use.

[Chris Rosenberger]

If you still have the vibration with the belts off, then the problem is with the motor or motor pulley.
If there is play in the tilt shaft worm gear, the vibration can cause the angle of the blade to change slightly.
You can check for play by lifting up on the end of the motor. You should feel very little, if any, movement in the end of the motor.
The play can be in the worm gear or the shaft, If you have play here, it is not the cause of the vibration but a result of it. You need to find the cause of the vibration.

You need to run the motor off of the saw. If the motor cord is long enough, you can just unbolt it from the saw & lay it on the floor.
You need to hold on to the motor when you turn it on, because it will want to roll when it is turned on. If the motor vibrates with the pulley on, remove the pulley & run the motor again.

[Jeffrey Kibler]

I ran the motor with it off the saw and it felt completely normal to me. It is almost like nothing has the vitration when the saw is taken apart.... but once you throw it all together it gets a harmonic. I'm almost to the point where i wonder if what I'm hearing is normal but it just doesn't seem right to me. The only place on the saw where i feel the vibration is when i put my had right below the rasie/lower adjust on the front of the saw. Oddly enough the worm gear for the tilt mechanism bolts to the saw directly behind that. If any of you place your hand in this area of the saw can you feel a slight vibration? With the motor off the saw I think things seem normal. That or i'm starting to lose my marbles.

[Phil Thien]

There is always SOME vibration. You aren't going to spin a blade to speed with a 5-HP motor using multiple drive belts and pulleys are get away with zero vibration.

And the Forrest blade does cut w/o any blade blades in the lumber.

Are you always using the same stock for your testing? Is the edge riding the fence perfectly straight, no bow?

If the piece of wood you cut w/ the Forrest had a nice straight edge, but you have used other test pieces when testing w/ the other blades (and if one or more of them have a bow) then I wouldn't be surprised if there are some blade marks.

How bad are the blade marks? Have any pictures?

[Jeffrey Kibler]

Yes I'm using the same type test pieces and yes the fence is aligned properly and straight.

I just spend 2 hours down in my shop and here is what I found:

1. Took the motor back off the saw, took the cooling fan and pullies and ran it bare bones. Motor sounded really good to me. Put the pullies and fan back on and motor still sounded really good. Sounded like the normal hum of a motor to me but no real vibration that i would call abnormal.

2. While the motor was off i tried pulling and tugging on everything under the saw and noticed that when i pull on the bottom of the motor mount (connected to the arbor at the other end) I can get it to move a little. The interesting thing is that it is only moving on the rear trunion support. The front where the tilt mechanism is, is rock solid. When i put the saw back together after the overhaul i did notice that there was zero wiggle room in the trunion support bolt holes, therefore it lined itself up where it wanted to with no adjustment. I didn't think a ton of it because I couldn't imagine me doing anything to the saw that would knock the trunions out of alignment.

I have also noticed that when I tilt the arbor I can not tilt it to the point where it really touches the 90 degree stop bolt. When I do this it actually move the entire trunion/arbor assembly up. It basically shifts it a little.

I will be interested to hear what people say about these trunion issues (if they are issues).

3. Put the saw back together with only one belt on the saw. The saw actually seemed to cut better, which didn't make any sense becuse i didn't really do anything. The harmonic/slight vibration was definitely still there though and I still saw the same effect when i tightened the lock knobs.

This problem is really frustrating. I equate this to having a tick or a noise in a car you have owned for 10 years. You notice it and it drives you mental because you know that car like the back of your hand. I know what the saw used to sound like and how it used to cut so I'm not giving up. I really don't want to have to take the top off the saw again but i have a feeling somebody is going to tell me there is an issue with the trunions.

Thanks as always.

[Phil Thien]

Something still doesn't add-up here.

You said your Forrest cuts "better than it ever has."

How is it that any vibration you're experiencing is only effecting the non-Forrest blades?

[Jeffrey Kibler]

I was actually talking to people I work with about that. When I bought that forrest blade like 7 years ago I remember not being happy with the cut and just stuck it in the drawer. I think I may have been a little judgmental back then. When I started dealing with the saw issues the last month or so I broke that blade back out so that I had three or 4 blades to do test cuts with. So I guess it is cutting better than it has in the last month. I don't know if my memory is good enough to compare it with what I saw years and years ago.

[Jeffrey Kibler]

I'm actually pretty shocked at how well this video picked up the sound. I broke down and took the saw apart again and really played around with it. My gut is telling me this vibration is coming from the motor and resonating through the saw but I don't see what could be bad on the motor other than the bearings. You can see in the video that when I very lightly press on the arbor it changes the sound of the vibration. You can also see then when I'm lowering or raising the blade the vibration pretty much goes away. Make zero sense to me. I realigned the trunnions and put everything back together and I don't think there is really a significant change. The video is taken with no belt and no blade so the only thing generating the harmonic is the motor. What the heck? I hope this video clarifies what I have been trying to say.
http://www.youtube.com/watch?v=K_o_z0EX1-M&feature=youtu.be

[Chris Rosenberger]

I believe most of that the noise is from the arbor casting & the worm gear. That is why it changes when you push on it.

Does it make an odd sound with the belts on?

Before doing the following, put the fan guard back on the motor so you do not get caught in the shaft.

If it does make the noise with the belts on, try pushing on the bottom pan in the cabinet while the saw is running.

[Jeffrey Kibler]

Nope no noise when I press on the base of the saw. Makes same exact noise/vibration with or without the belts. I have even switched out and tried different belts, just one belt, and different blades. Still does the same thing. I have the top and the extension wing back on the saw. The sound is different now after tearing the saw apart and putting it back together but it is still there. I can take another video but the noise still seems very harmonic... there is a consistent beat to it.

[Jeffrey Kibler]

So I took the motor off the saw and took it to an authorized baldor service center to see what they think. They said they will probably have it back to me in about a week. The guy was actually shocked that I was bringing in a motor that basically looked brand new and that I was having problems with it. If he tells me there is nothing wrong with it then i'm back to square one. Actually I'll probably move to the square where I sell the saw. On a side not I got the Powermatic 2800B drill press yesterday and will probably start a new thread with a review sometime later this week.

[Jeffrey Kibler]

I got the motor back and they said there was absolutely nothing wrong with it. I cleaned everything back up, put the motor back together, leveled everything back out, and bought a forrest blade stabilizer and everything is what I would call acceptable now. The stabilizer is just masking the real problem but it is allowing me to make clean cuts so I don't really care. I may start looking to sell this saw and get a laguna. After getting the 16HD bandsaw and comparing the quality of this product to my PM machines they are in a completely different class as far as I'm concerned (using the 16HD as my only reference point).

[Doug Ladendorf]

Seems like something may be slightly loose in the trunnion assembly. When you apply pressure with your hand it quiets. Try tightening everything up?

[Peter Quinn]

There is a two piece arbor retainer clip, like a snap ring bit in two interlocking pieces, that holds the arbor in place relative to the throat. They fail. When mine failed it fell off into the cabinet, and I just barely noticed it lying in the bottom of the cabinet while doing some cleaning, which I was doing in prep station to investigate why my cuts were getting a toothy look. I eventually found both halves, realized my arbor was shifting slightly under load due to retaining clip being gone. Stupidest design I've ever seen, I replaced it with a solid c clip which was harder to instal in close quarters but also harder to break. Any chance yours is missing? Check your parts diagram, it sits just past the 3 sheaf pulley on the outside of the trunion, it would not be obvious something were missing other than a thin slot in the arbor shaft.

[Jeffrey Kibler]

All the parts are there but I think you might be talking about a different version of the PM66 than I have. The only thing I have that locks my arbor in place is one set screw.

[Jeffrey Kibler]

So i'm not sure if anyone is reading this thread or anyone still really cares but after months and months of playing with this saw i'm happy to say IT'S FIXED. Even though it made no sense to me, I finally ran out of ideas and broke down and bought a pre-assembled arbor assembly. Actually the first one I got from Powermatic was defective and I had to get another one. But finally today I got the replacement, hooked it up, and the saw literally cuts like butter. Not one single solitary blade mark can be seen and you can hear that the saw is running well now. So I guess all I can say is, if anyone out there starts running into this problem and you don't mind spending the cash, you may save yourself a lot of headache by just buying the whole assembly as opposed to replacing bearings. I will never understand how the arbor got out of round or bent but at this point I don't care. I couldn't be happier that the saw is working again.

[Jeffrey Kibler]

And now i'm officially frustrated. After less than I week I can tell the saw is starting to revert back to its old ways. The day I replaced the arbor assembly it was working flawlessly. Very smooth operation and the blade never made a single noise flying by the zero clearance insert. Now less than a week later I can start to hear it vibrating a little and you can hear it ting up against the zero clearance.... when translates to blade marks on the wood. I'm endlessly frustrated and thinking about getting rid of the saw. I don't know what to do at this point and it makes me sick that for what I spent on that saw the piece of crap didn't even last 10 years. And this one was made in the USA.

[John McClanahan]

Try running with just 1 belt and see if it makes a difference.

John

[Jeffrey Kibler]

I will give the one belt a try today but I fundamentally don't understand why I should have to do this. The saw worked great for years and now all of the sudden I have to try all these things to make it work right. Why all of the sudden should I have to switch to one belt when two worked perfectly for years. I just don't get this and I think I'm in the minority of people now that are extremely disappointed with the PM66. I'm also disappointed that PM tech support literally has zero suggestions. I'm tempted to find a professional tool repair guy (if that exists) and have them come take a look at it, but I'm a pretty mechanical guy and I don't know what they are going to do differently. I'm literally sick to my stomach that I have thousands and thousands of dollars sunk into a saw that in my eyes is now garbage.

[John McClanahan]

My PM66 runs smoother with just 1 belt. New belts may fix my problem, but I don't use my saw hard so I just run with 1 belt.

John

[Lewis Ehrhardt]

have you checked the voltage going to the motor?