Unisaw motor shaft "wobble"

[Jim Ryder]

I recently acquired a 2005 5hp, 1ph, Unisaw for a great price. It was used commercially for about 2 1/2 years. In the process of cleaning it up I noticed that the v-belts were dry and cracked. After I removed them I decided to run the motor just to check it out. It seemed to run fine and the pulley wheel seem smooth while running full speed but when I shut it off, right before it stopped rotating I noticed the pulley wheel wobbling. If I rotate the shaft manually the wobble is noticeable but again, at full speed it doesn't appear noticeable at all. With the belts attached it runs fine and smooth as well. Is this cause for concern down the road? Is there a way of straightening out or replacing the motor shaft? If I have to purchase a new motor that wouldn't be out of the question since I got such a great deal but I'd rather not.

[Jim O'Dell]

I would think if it was a shaft, it would be worse at high speed. I'm not an electric motor guru though. My guess is more a motor bearing problem. With the belts off, if you grab the motor pulley and push/pull up and down (perpendicular to the shaft) do you feel any movement that would suggest bearing problem? Jim.

[george wilson]

Are you sure its not the pulley being bored off true rather than the shaft? Also,the motor shaft could have been bumped hard before it was even put into the saw. If it isn't noisy,I'd assume the bearings are o.k.. Could you replace the pulley? It isn't the very best thing for bearing life if something is wobbling all the time.

[Jim Ryder]

Thanks for your responses... I was planning on purchasing a wheel puller on my way home from work tonight to remove the wheel for further inspection... I'll also push/pull the shaft for possible movement.

[Chip Lindley]

Jim, with the pulley off the motor, you will be able to tell if the shaft is bent, or the pulley is at fault. Could be that the set screw worked loose and allowed the pulley to wear the shaft out of round. This would be the worst case scenario if both motor and pulley are damaged. If you are lucky that the motor shaft is still true, a Grizzly pulley will fit the Unisaw, and cost far less than a Delta replacement.

I believe George Wilson shared how he re-machined a motor shaft by building it up by welding, then machining it to exact diameter, and cutting a new keyway. Wish George was in my neighborhood!!

[Jim Ryder]

Well I finally got the pulley wheel pulled off of the motor... the first night I got it moved about a 1/16", then I put penetrating oil on and the second night I got it moved about 1/2" and then the wheel puller jaw teeth started breaking (bought a cheap puller from Harbor Freight... big mistake, I know.) Bought a much better quality puller this weekend and finally got the wheel pulled off. There was dried up grease inside the wheel that made it very hard to pull off. Also, the key is damaged. I appears to me that at one point the saw may have gotten bound (is that possible on a 5hp saw?) and the pulley wheel shifted and compressed the key. The motor shaft keyway is slightly damaged but not bad. The end of the shaft is within about .002. Not sure if that is alot but I'm leaning toward the idea that the wheel is out of balance. Also, I can only get the wheel to mount on the shaft from one side. The other end is obviously out of round. I'm thinking the best route would be to simply replace the pulley wheel and key. Thanks for all the input!!!

[Chip Lindley]

Jim, it could be worse! At least the motor shaft is not *eaten up* and still intact! .002" runout at the motor shaft end is not perfect, but may be acceptable with a new pulley. The keyway can be judiciously filed smooth to remove any burrs and a new key mounted.

At one time the pulley may have been loose on the shaft, and each time the saw was started, the key slammed into the edge of the keyway, leaving it in the shape you found. That may not be dried grease, but LocTite that someone used to *FIX* the loose pulley on the shaft. Just a guess.... Good Luck getting the big 5hp motor back in operation!

Edit:Next time try a little heat when a pulley is this difficult to remove. LocTite's bond can be broken with heat from a propane touch, taking care not to overheat and ruin bearings or wiring.

[Jim Ryder]

Thanks Chris for that advice and I think you're exactly right that the key kept slamming up against the keyway.... given the key's condition that's exactly what looks like must have happened. I'm curious though... how "loose" should the wheel be on the shaft. Right now it spins more freely than I feel it should. Is using LocTite when I put the new wheel on a good thing to do?

[Dave Beauchesne]

Thanks Chris for that advice and I think you're exactly right that the key kept slamming up against the keyway.... given the key's condition that's exactly what looks like must have happened. I'm curious though... how "loose" should the wheel be on the shaft. Right now it spins more freely than I feel it should. Is using LocTite when I put the new wheel on a good thing to do?

Jim:
What should probably happen is to mic the shaft and see what the diameter is in relation to the sheave ( pulley ) I. D..

Using Loc Tite is a last resort, and I have done the same in my trade when the motor is fine, and it is a last ditch repair. Use the right product as well; there are specific products for ' large gap ' repairs - not all the products will be satisfactory. Be sure to follow the directions to a '' T ''.

If that is the way you decide to go ( and I would try to get a Millwright or Auto Mechanic buddy if available for a consult ) have a dial indicator to check the final assembly for wobble before you let it cure. Also, tag the motor as to what you did and with what product for you or the next guy later on.

Dave Beauchesne

[Jim Ryder]

Opps..sorry about that Chip... I just realized that I called you by the wrong name.... my son's name is Chris and it's just what immediately came to mind when I saw your reply.

[Jim Ryder]

Good advice... I was thinking about calling a local electrical motor shop to see if they have a way to get a pulley wheel balanced.

[george wilson]

Does the pulley need balanced,or is it just not running true ? Was it not machined true ?

there needs to be about .001" clearance between the shaft and the pulley. In metal work,a pulley that is the SAME size as the shaft won't go on the shaft (unless you can press on an "interference" it,which does not apply here.


Please answer my question : is the pulley just not machined true ? On a 2" pulley,I wouldn't be too concerned about it not being balanced.

I would NOT use Loctite on the pulley. It isn't appropriate to glue the pulley on.

[Jim Ryder]

I'm not sure if the pulley wheel is true but I'm guessing it's not. My impression is that it was possibly distorted from hard use... is that possible? As I said in my initial posting, the wheel appeared to run smooth when at full speed and no belts attached. It was during the last few seconds when the motor was winding down that a discernible amount of wobble was noticeable. The outside hole of the wheel appears to be distorted as it won't fit on the shaft but the original inside hole will and it slips on very easily... with a slight degree of play as well. In fact I can rock the wheel back and forth slightly even when almost full attached. this doesn't seem right to me which is why I feel it should be replaced. Oh also, the wheel size is 3 1/2"... with three v-grooves... the usual Unisaw configuration.

[Myk Rian]

Your initial post indicated that you couldn't see wobble with the motor running, but did when it was winding down.
You won't see it when running because it's too fast.
Did you take a dial indicator to the shaft? That will tell you if it's the shaft or the pulley. Do that first, then you'll be able to stop guessing what is wrong.

[Chip Lindley]

No Problem Jim, I've been called Chris or Chuck my whole life. I even answer to it! LOL!

If you can wiggle the pulley discernably by hand while on the shaft, it is Trashed! Reason the shaft will not slip into the opposite pulley end is probably due to LocTite still in the bore. A moot point.

A pulley should fit on it's shaft with a very close sliding fit. There should be no play at all! It may even take tapping with a block of wood to fully slide the pulley onto the shaft with key installed. Removing with a puller should not take near the effort your experienced.

IMHO, you might as well consider a new pulley. (one listed on ebay just today off a 5hp Unisaw!!) I fear the bore was worn larger by being run *loose* on the motor shaft for a long time, before someone decided to *fix* it. Inspect the motor shaft for damage. Signs of wear should be very obvious. I am hoping the pulley took the brunt of the wear and not the shaft.

[Dave Beauchesne]

Does the pulley need balanced,or is it just not running true ? Was it not machined true ?

there needs to be about .001" clearance between the shaft and the pulley. In metal work,a pulley that is the SAME size as the shaft won't go on the shaft (unless you can press on an "interference" it,which does not apply here.


Please answer my question : is the pulley just not machined true ? On a 2" pulley,I wouldn't be too concerned about it not being balanced.

I would NOT use Loctite on the pulley. It isn't appropriate to glue the pulley on.

Jim:

George's point is valid in regards to ' glueing ' the sheave onto the shaft; that being said, if the keyseat ( keyway ) is mangled and the shaft itself if compromised, AND the motor itself is functional, well, then, I would use a compound to ' take up the slack ' so to speak.

The motor shop should be able to send you in the right direction, however, they may want to sell you a new motor rather than get yours functional.

Dave Beauchesne

[Jim Ryder]

I just mic'd the shaft and it measures from about .741 at the base to .746 near the top. I'm not sure what a new pulley hole size would be but I'm going to guess that it's going to be around .750 to .752... am I close? The shaft tolerance doesn't seem particularly good to me and does almost seem to point to some degree of wear even though it doesn't look that bad.

The motor is very functional and I'd rather do whatever I can to make it work.... but what kind of compound would work for filling in a gap?

At this point the first thing I'm going to do is contact a motor shop just to see what they say. If all they want to do is sell me a new motor then I'll probably buy a new pulley and key and see how it operates with that though I suspect it's going to be a loose fit and I'll have to use some sort of compound.

[Chip Lindley]

Jim, I was afraid of that! With measurements of .741" to .746", the best solution would be to have the shaft built up by welding, then machined to correct diameter, and the keyway recut.

2nd best: have the shaft turned down on a lathe for a good fit with some standard shim stock between the smaller diameter shaft and pulley bore.

3rd best: insert a shim sleeve of .002 or .0015" shim stock (I found an assortment at Grainger) around the shaft (except the keyway) to fill the gap. When you fit a new pulley onto the shimmed shaft, Then use the appropriate LocTite to afix everything.

[Jim Ryder]

Thanks Chip for those suggestions... very much appreciated! Unfortunately I don't have the ability to personally manage the first two options so I'll see if the motor shop can do either. If not, then I'll definitely tackle your third suggestion as I know I can handle that.

I'm a hobbyist woodworker so I'm not likely to put the table saw to any where near the rigors that it once lived through but it is always nice to have equipment running as smooth and true as possible. I'll be sure to follow up with what results I end up with... thanks again!

[george wilson]

I recommend the use of shims. There is no way you could guarantee the even thickness distribution of any liquid,or paste filler.

A motor would cost quite a bit. Several years ago a 3 h.p. one was nearly $400.00. If there is no vibration at full speed,you could just use the setup as is. No vibration when running isn't so bad,is it ?

Make sure the keyway is good and tight. The shaft wearing so badly was caused by something. Perhaps the pulley slapping around on it for some time. Are you planning very heavy use of the saw? It could last quite a while as is, but better with some shims on the outboard end.

If someone could turn the shaft down till it's parallel,and take a 5/8" bore pulley,them bore it out to fit the odd size shaft in a lathe,you'd be fine. Keyway would have to be filed down a bit.

Are you close to Williamsburg ? I could turn it down and bore out the pulley for you if you take the armature out of the motor,get a pulley and get it here.