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Replacing Bearings on Powermatic 66

mapleman's picture

I'm beginning to notice my 5 hp powermatic 66 seems to be making quite some noise lately, and I'm thinking it may be coming from the arbor bearings.  I measured runout with a dial indicator and it seems to be in the .004-.005 range.


My first question is, is that tolerance normal? I can't see where it is a problem with the cut quality.


My second question is, how loud are these saws normally? I only have a sears craftsman direct drive 2hp saw ( mid 1970's) to compare it to, and that thing is dead quiet. (I know I'm comparing apples to oranges here) I wish I could post a sound bit of the noise here for you to hear. It's not a squealing or metal on metal sound, just like a loud rumbling. Very loud in my opinion. The saw is a 2001 model that I bought used, however it was only used for about a year by the previous owner and looked to be brand new when I got it.


If I can determine that the bearings need to be replaced, how hard is that to do? Will I need the help of a machine shop to press the bearings in? Will I need to remove the saw's top? It seems like I can get to the arbor shaft without removing the top, which I would rather not do.


Would any of the noise be coming from the belts? Seems unlikely, and the belts appear new, and not worn at all.


Can the bearings be lubricated? I don't see a way to  or mention of that in the owner's manual.


How hot should the arbor nut/blade be after use? I have changed the blade immediately after use a few times and noticed the arbor nut/arbor and blade were fairly hot, but I assumed this was normal from the cutting. Not sure how hot is too hot, or if hot at all is a normal thing.


Sorry for all the details, but I figured the more info I gave, the better it would be for someone trying to help.


Any and all help would be greatly appreciated.


Lee

tinkerer2's picture

(post #100054, reply #1 of 26)

Wish I could give you more help, but since no one else had chimed in, I'll say what little I can.  I have the PM66 3HP.  It runs very quietly.  I've never run it without a blade on but I would guess that almost all of the noise comes from the whisper of the blade.  In fact, with my hearing as it is I can't detect any sound other that the blade and maybe a little buzz from the motor.  Hard for me to picture the bearings going out this early.  My guess is the belts.  I've never tried changing them or hardly looked at them but would surely think they would be easier to change than the bearings.

dgreen's picture

(post #100054, reply #2 of 26)

Check the set screw on the arbor pulley. If it is loose it will cause a rumble such as you described.

------------------------------------


 The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer (1891)

 

 

................................................

Men will never be free until the last king is strangled with the entrails of the last priest.
~ Denis Diderot

QCInspector's picture

(post #100054, reply #3 of 26)

A couple of thoughts to help with your trouble shooting.

If you haven't't already done so, take the blade and washers off and turn on the saw. This will remove the noise that the blade makes and perhaps let you pinpoint the location of the noise that concerns you.

Next take off the belts and turn on the saw and listen again. That will take out the arbor and possible belt noise, and let you know if the motor bearings are not part of or the cause of the noise. With the belts off spin the arbor by hand and if you feel any roughness or hear any noise then it's the bearings.

You mentioned the arbor nut being hot. That's a clue that the bearings may be a problem.

Before you order bearings from Powermatic, take the ones you remove to a bearing supplier. They can determine by the numbers on the bearing or by measurement which ones you need. They are probably standard bearings and if they don't have them in the building they will be able to get them within a few days for a lot less than the ones from Powermatic. Same applies to the motor bearings if they need to be changed too.

You may not need special tools to change the bearings but if you know any friends that work on cars they will probably be able to get them out and in again without to much trouble.

tinkerer2's picture

(post #100054, reply #4 of 26)

Good standard approach.  Why didn't I think of that?

terrylee86's picture

(post #100054, reply #5 of 26)

Lee,


I replaced the arbor bearings on PM66 two years ago.  Follow the advice of QCInspector before you try my advice.  I will explain how to replace the arbor bearings on a PM66.  It is not that bad of a job if you just take your time.  I don't think it is normal for the arbor to get hot so it might just be the bearings.


I don't know if you can extract the arbor without taking the table off ( I didn't even try), but it might be worth a try.  Working inside that cabinet seems like a nightmare, but maybe you are smaller then I am.  The first step is to remove the motor and belts.  Then remove the motor pulley and the set screw that holds the center bushing of the arbor in place.  It is on top of the casting so I don't know if you can reach it with the table on.  Then gently tap the arbor out with a block of wood to protect the threads.


The arbor has two bearings and a spacer bushing and the blade flange pressed onto the arbor.  A buddy had an arbor press so we just pressed the bearings off with the press.  He got carried away and pressed of the flange and that was a nightmare to get reset properly.  The original bearings on my saw were shielded(metal jackets) get sealed bearings to replace them.  They cost a little more, but not much.  You can replacement bearings at a bearing supply house (Detroit Ball Bearing for me) and they had them in stock.  They are not cheap as I remember, but I bought the best line they carry.


Tap the assembly back into place and reverse the process.  Make sure you measure or make a gauge block to know the distance from the flange to the casting or your blade will not line up with your inserts.  Taking the table off is not that bad (four bolts) but it is definitely a two man job.  It took me three days of tinkering to get everything right.  Most of that time with the stupid flange.  Good Luck


 

DavidCockey's picture

(post #100054, reply #6 of 26)

If with the belts removed there isn't any detectable slop in the arbor, and it doesn't have any rough spots when you spin the arbor by hand then it's likely not a problem with the bearings.


Check the tension on the belts. If too loose they can flap and make noise.


I'd replace the belts before the bearings. That will be much simplier and should be less expensive.


Do you know anyone else with a cabinent saw that you could visit and compare how loud your saw is to their's. Your saw might not have anything wrong with it.

waljay's picture

(post #100054, reply #7 of 26)

Mapleman:  The heat and the noise indicate that likely the bearings are on the way south.  Yes, you could change a lot of other peripheral things but bottom line, the bearings are as you suspect.  I agree that five years is not very long but the bearings may have been in distress from day one.  A sealed bearing certainly extends the life of the rollers or balls but again, one or both could have been marginal when they were installed when the saw was new.  I certainly would not be hammering or banging during the disassembly or assembly procedures.  Buy the bearings and find a machine shop who has the presses to do the job right.  When you start banging a bearing on a shaft, two things can happen, neither one good:  you can marr the shaft by hammering the bearing on crooked, or you can damage the bearing itself.  A machine shop has experienced people (hopefully) and know what pressing a bearing off and on.

mapleman's picture

(post #100054, reply #8 of 26)

Thanks to everyone for some outstanding advice. I have a few more cuts to make with the saw tonight and then I will be sanding/staining/finishing for a few days or a week. First thing in the morning I will start at the top of the list with Don's advice to check the arbor set screw and then go down the list. I never thought to disengage the belts to isolate the motor from the  arbor.  I will post back to let everyone know what I find out.


Thanks again,


Lee

mapleman's picture

(post #100054, reply #9 of 26)

OK, here is an update on what I found:


First of all, hats off to Don. The arbor pulley was loose, sliding back and forth on the arbor shaft after the belts were removed. I was able to tighten the pulley, however, that made no decrease in the noise level.


Belts off, the motor purrs like a kitten, quiet as a whisper.


The noise is slightly better/less loud with the blade (forrest wwII) off. I tried a different blade (freud 30 tooth rip) and the noise was the same as with the forrest blade.


Spinning the arbor by hand I can detect no slop or roughness. However, I can hear what sounds like tiny bb's rattling or smacking up against each other. Very faint, but I can hear it. I am wondering if the excessive heat caused by the loose pulley (that is definitely where the heat was coming from-it went away when I tightened the pulley) cooked the bearings?


I am still tempted to change the belts, because of the low cost, but I don't think that is the source of the problem.


So, if I change the bearings, I need to know a few things. Here is the powermatic manual's explanation on how to replace them:


Arbor and arbor bearing removal:


1. To remove the saw arbor, first remove the mounting screws holding the table top to the base. Lift off the table top.


2. Loosen the two setscrews in the motor pulley and remove the pulley and key. (I think they mean remove the the arbor pulley, not the motor pulley)


3. Loosen the setscrew at the saw raising arm and the arbor assembly and bearings will slide out of the arm housing


Now, do they really come out that easily? Another poster suggested getting the bearings pressed on, I am assuming you would take the arbor assembly to the machine shop, and not remove the raising arm assembly? That looks like a fiasco, half the saw would have to come apart.


Should I get the bearings from powermatic or look at a bearing supply house instead? I would hate to get new bearings pressed on and get home and something is not fitting right. It would seem easier to get replacements from powermatic, and know they are right (or hope they are). I am sure they are not cheaper at powermatic, however the only way to get the # off of the bearings (to get them locally)is to remove them, at which point the saw is inoperable. If I order from powermatic, I have the part # in the manual. Here is the main point I am considering, which over-rules cost or ease in obtaining the bearings locally: Which bearings are higher quality, and how do I tell? A previous poster mentioned that some bearings are a higher quality.  I only want to do this once.


Lee


 

philip's picture

(post #100054, reply #10 of 26)

Lee,
When you can hear that ticking/clacking sound as you turn a ballbearinged shaft by hand it indicates that the bearings are going dry or that the lube is very thin-but in your case those bearings are probably sealed ones so they are going dry.Whip them off-common ball bearings are cheap.Real mechanics will whip them out , pick off the seals and re-lube them if they are in this condition and not running rough- but since they are cheap it is easier to get new ones.
When a manual says something like "they will slide out"- it usually means that they are not an interference fit and you can just tap them off the shaft or out of their housings- in other words no need for presses etc or much force.When you put in the new ones be sure to have the housings and shaft clean-especially no burrs. If you can find a pipe or tube that fits over the shaft then use this to tap them on, so that the pipe is bearing on the inner ring. When you put bearings into a housing be sure to tap the outer ring only.
Quality? These will be common ball bearings but if you stick to known names like Fag, Timken , SKF etc you should be alright. Get the ones with integral plastic seals rather then the metallic dust shields. If you buy from a proper bearing mearchant it is best to show them the old ones - they have numbers on them which are there for a reason.If you buy from Powermatic chances are you will pay more .
Woodworkers who have machines should get to know about bearings-how to maitain them, change them , tweak them etc.Where would mankind be without bearings? Wood dust likes to kill bearings so it pays to have an interest in them.(Actually they fascinate me , but then I am known to be mad).
Another thing about going to a proper mearchant- you can get bearing catalogues from them with all info on bearings, sizes , applications, loads, lube type etc.I have the SKF general catalogue book 450pages of most useful stuff.
I would think that the Powermatic is similar to Delta Unisaw, in which case successful replacement of bearings is a breeze-just take your time and do not force things.

Philip Marcou

Philip Marcou
dgreen's picture

(post #100054, reply #11 of 26)

If you can give me the model and serial number of the saw I'll see if I can get you part numbers without you having to take the saw out of service.

------------------------------------


 The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer (1891)

 

 

................................................

Men will never be free until the last king is strangled with the entrails of the last priest.
~ Denis Diderot

mapleman's picture

(post #100054, reply #16 of 26)

Hey Don,


Thanks for the offer. I was lucky enough to get the owners manual with the saw, so I have the part # info. Just had to google the WMH phone #. By the way, the tech guy was extremely helpful and very knowledgeable (did I spell that right?) A pleasant surprise.


Lee

terrylee86's picture

(post #100054, reply #12 of 26)

Lee,


As I mentioned in my previous post, the arbor will slide out of the arm quite easily.  You may have to tap it, but that is all.  You will have to press the old bearings off and the new onto the arbor shaft.  Again, take special care not to move the blade flange.  Powermatic does not make bearings, I just took the old ones in to Detroit Ball Bearing and they gave me the right size.  I ask for premium bearings and I think they gave me NSK's (not sure), just get sealed (plastic jackets) and not shielded(metal jackets).


Check the arbor shaft to make sure the loose pulley did'nt ruin the shaft and the keyway.  You might be right, the heat from the loose pulley cooked the grease out of the bearings and they are now dry.  Replace them don't try to lube them.  You might want to replace the belts if they have been slopping around that long.  I used Gates green belts when I rebuilt my saw, not sure if I need them but when it was apart why not?   Make sure you put the arbor back into the exact spot so the blade is still in line with everything.


Terry

mapleman's picture

(post #100054, reply #14 of 26)

OK guys,


Just got off the phone with powermatic. New main arbor bearings are $23 each (X2) and the roller sleeve bearing between them is $19. Or, I can buy the whole arbor shaft assembly with a new arbor and all the bearings pressed on for $71 + $9 second day air shipping. Which  I could slide back in the saw and be back on the road to cutting. Seems like that is the best option. I did call a bearing house in New Orleans first (about 60 miles away) and they said it was likely they would have them in stock, or could get them in a day or two. I would think their price on just the bearings would be half of powermatics, but then with the gas, etc it probably would end up costing $40-$50 plus my time, before any machine shop charges. Then I could still rebuild my old one for a spare. I like the idea of being able to do it myself, as Phillip suggested.


What do you guys think?


Lee


Edited 11/28/2006 11:57 am by mapleman

PeteBradley's picture

(post #100054, reply #17 of 26)

Buying the whole arbor with bearings is certainly the simplest.

If you do want to do the swap yourself, it should be pretty straightforward. I get bearings from Accurate Bearing http://www.accuratebearing.com. Ask for Nachi or some quality brand. Don't buy bearings from places like the hardware store or McMaster as the quality may not be too good.

Purists avert your eyes now:
You can probably replace these bearings without an arbor press. You can most likely pull the old ones off with a puller. The bearing will be destroyed, but it's a throwaway. There are also cave man ways to get the old one off, such as hanging the shaft loosely in a big vise by the bearing and whacking it through with a plastic mallet, but they put the shaft at risk. Don't whack the end of the shaft with a metal hammer as you will mushroom it.
I.D. id slightly larger than the bore of the bearing. Stand one end of the arbor on a block of wood on a concrete floor, slide the bearing over the other end, slide the pipe over too (be sure the pipe only contacts the inner race of the bearing), and drive the bearing home by tapping the pipe with a dead blow mallet or hammer. Do the other end the same way.

When reinstalling the arbor, make sure everything is clean, and be careful not to put much axial load on the bearings as hey go in. Gentle taps with a dead blow hammer are all that should be necessary.

Pete


Edited 11/28/2006 7:37 pm ET by PeteBradley

RickL's picture

(post #100054, reply #18 of 26)

Mcmaster sell quality products. Been buying from them for years. I get my bearings from http://www.bearingbrokersinc.com/index.html. I paid $1.50 each for Nachi bearings to do the last 3 unisaws I replaced the arbor bearings on. You certainly don't need an arbor press to do this. I have a simple puller I use in the field to remove bearings. You can gat an import puller for occassional use for no more than $20.

I'll have to compare prices with accurate bearings but I can't imagine they could be much lower than bearing brokers prices. I bought some precision bearings to repair a wadkin moulder for $150 each and wadkin and other sources wanted $300 each. They were the original brand bearings from bearing brokers so it was apples for apples.

PeteBradley's picture

(post #100054, reply #19 of 26)

I buy from Mcmaster too, just not bearings. Looks like you do the same. Lots of sources to choose from.

Pete

RickL's picture

(post #100054, reply #20 of 26)

I probably order from mcmaster several times a week. They are the the most professional people I have ever dealt with. They have been in business over 100 years and do not advertise which says a lot.

terrylee86's picture

(post #100054, reply #21 of 26)

Lee,


If you can buy the whole arbor for $80 that is the way to go.  It will cost that much in time and gas to go to N.O.  I think you would save yourself a lot of headaches.  I have a good friend that owns a machine shop.  That is how I saved money.  Your arbor shaft may be bad on the pulley end anyway.  Buy the whole assemby.


Terry

mapleman's picture

(post #100054, reply #22 of 26)

Hi Terry,


That's what I did. Should be here tomorrow. I bought the pulley as well, because I went back under the saw just sort of fooling around and noticed the pulley was loose again after I had tightened it. Well, it seems to be so far out of whack and wallowed out that it wobbles a good deal without the set screw in. Seems it should fit fairly snug and when you tighten the set screw, lock down tight. I didn't want to get a new arbor only to find out the pulley was wasted, so I called powermatic back and had them add the pulley to the order. I would assume the steel on the arbor is harder than the steel on the pulley, so that the easier to remove and replace pulley would wear first?


Lee

terrylee86's picture

(post #100054, reply #23 of 26)

Lee,


Good Luck.  Like anyone setting a up a good experiment, you eliminated as many variables as possible.  I think your PM66 will purr right along now. Mine does and my son just loves the saw. ( right price $0)

TKanzler's picture

(post #100054, reply #13 of 26)

"Now, do they really come out that easily? Another poster suggested getting the bearings pressed on, I am assuming you would take the arbor assembly to the machine shop, and not remove the raising arm assembly? That looks like a fiasco, half the saw would have to come apart."


Speaking in general terms, the part of a bearing with the load always in the same direction will have a looser fit, i.e. not an interference fit.  The outer race of your saw's bearings are always loaded (radially) in the direction of the belts and the line of action of the cutting forces on the blade teeth (or some combo thereof). 


The part of the bearing with the load that rotates will have an interference fit.  The arbor, and the inner race, rotates.  Since the forces are always in the direction of the belts and blade cutting forces, the load on the inner race is 'rotating' - if you stood on the shaft, the world (and the belt/blade forces) would be rotating around you.


So the outer race will have a 'loose' (clearance) fit, loose enough to be gently tapped out with a mallet and block of wood.  The inner races will have to be pressed off the shaft, and the new ones pressed on.  It is supremely important that whoever does the work only presses against the inner race - you can ruin bearings by putting that kind of force through the rolling elements (most likely balls, in this case).  Anyone who knows what they're doing will have the right bearing separators and fixturing to do this the right way.


So the arbor and it's bearings will come out of the casting with relatively little effort (outer races), but to get the bearings off of and back onto the arbor will take a press (inner races).  If you can hear the bearings when you spin them by hand, like the sound of the wheels of a wooden roller coaster on the metal-clad rails, they're dry and/or otherwise failed. 


As an aside, wheels work the opposite way from rotating shafts - the load on the outer race rotates, and the load on the inner race is always in the same direction.  That's why the outer races are pressed into the hub, and the inner races are a clearance fit to the spindle.  If the part with the rotating force was allowed to move relative to the bearing race, it would eventually wear and become sloppy.  Bearing fits are generally controlled very precisely, as are the dimensions of bearings themselves.


Be seeing you...

Be seeing you...

mapleman's picture

(post #100054, reply #15 of 26)

TKanzler and Terrylee,


Thanks for the clarification. I was thinking the arbor assembly would have to be pressed out of the blade raising mechanism. I am the type of person who enjoys taking things apart to fix them and then putting them back together, but I like to have more info than I will likely need before I start.


Lee

JerryPacMan's picture

(post #100054, reply #24 of 26)

I would use a new set screw when installing the new pulley.  I always use a longer serrated end set screw and blue Locktite.  You will probably notice that the set screw does engage all the threads in the pulley.  I use a longer one as you have more contact area for the Locktite.

 


Life is what happens to you when you're making other plans .

 

Life is what happens to you when you're making other plans.

When your ship comes in... make sure you are not at the airport.

mapleman's picture

(post #100054, reply #25 of 26)

Hi Jerry,


Great idea. I had thought of using the (blue) loctite when I replaced the screw. I hadn't thought of the longer screw, you are right, it is very small and does not contact the threads much. That is the first lock screw I have ever seen with the serrated end. Any idea where to get a replacement? Is that a regular item at hardware stores?


Lee

JerryPacMan's picture

(post #100054, reply #26 of 26)

A good hardware store might have knurled cup point set screws.  I use stainless steel knurled cup point set screws that I get from McMaster-Carr.  I have a good assortment on hand as even on new machines I replace the set screws.

 


Life is what happens to you when you're making other plans .

 

Life is what happens to you when you're making other plans.

When your ship comes in... make sure you are not at the airport.