Discovered loose pulley when installing link belt on table saw. How to fix?

[Owen Lawrence]

Hi. I finally decided to replace my table saw drive belt with a link belt. When I removed the belt cover I discovered that the pulley was loose on the motor shaft. The only thing keeping it on was the belt rubbing against the inside of the belt guard/cover. That part of the cover is nicely polished now. :)

I have realigned the motor so the cover fits better, but I'm still having trouble keeping the pulley on the shaft. There's a key in the key slot, and a set screw in the pulley that I've tightened down as much as I can. It might hold this time, but the first few tries it came loose after only a few seconds under power.

There doesn't seem to be any mechanical fixture for keeping the pulley from sliding on the shaft. Should I put some loctite on it? (I've never actually used loctite myself; what kind should I get?) Or is there a better way?

The instruction manual just shows a photo of someone pounding the pulley onto the shaft with a hammer and a block of wood. I'm way past that now. There's some blue coating on the last 1/2" of the shaft. If I don't position the pulley near the end of the shaft there isn't enough clearance inside the belt cover. It seems like it would be better if the pulley were closer to the motor housing (and bearing). I sometimes hear a clicking noise, once per revolution, as the motor spins down. It didn't do that before, and I speculate it started because of the repositioned pulley.

What's your best advice? Thanks.

- Owen -

[Phil again]

I have always read instructions that the two furthest away edges of the two pulleys are to be aligned to a straight edge. Sometimes that requires adjusting both pulleys on their respective shafts. Drive belt should be centered in the opening of the belt cover, per my old craftsman TS instructions.

The forces on the drive belt usually are to the shortest distance between the two pulleys and all that. Also check the shafts of the arbor and the motor are both at 90 degrees to the rotation plane of the drive belt (or as best as you can do sometimes.)

Check the end of the set screw, it should be flat or slightly convex. the idea is to maximize the surface area of the set screw; maximum friction when tightened down. Set screws are cheap to replace. If in doubt, replace set screw.

Just think slowly through how to reduce the forces that will cause the motor pulley to wander across the shaft. It should not take a very large force to keep the pulley in place.

BTW: there is a home made tool involving a screen door turn buckle, threaded rod, and scrap wood that will stretch the two pulleys apart as you adjust the motor shaft, and align the two pulleys. Fist time I use such a tool my band saw drive belt noise reduced to almost nothing.

good luck.

[Zz Yzx]

When I bought my link belt "system", it came with new "premium" pulleys. And they worked REALLY well. I'd look into replacing the pullies.

Before the change, my saw couldn't pass the nickel test with the nickel laying flat. Now it passes with the nickel on edge.

-Zz

[Lew Hodgett]

I'd replace the sheave (pulley).

It's probably die cast aluminum and damaged beyond repair.

Position the new sheave as close to the drive end bearing as possible and use some LocTite on the set screw to insure it stays in place.

Adjust motor on mounting plate as required to line up with sheave on the blade arbor.

As far as the belt guard is concerned, I'd probably s**t can it, but that is your choice.

A transmission house or Grainger will have both the sheave and LocTite.

Have fun.

Lew

[Artemus]

"Owen Lawrence" wrote ... [snip]

[snip]

A new setscrew usually solved the problem for me. They are cheap and available at most HW stores. In stubborn cases I've doubled up and put a second setscrew on top of the first. Shorter length setscrews are avail ... This has never failed to hold. Art

[BDBConstruction]

The clicking is the slight bit of slop in the loose shaft/key/pulley. It is something to listen for in the future when you use your saw as you will know the pulley is loosening. I would say the reason why the set screw is no longer holding is because often times the set screw will form a depression in the key. The setscrew will want to locate in this depression when you try to reinstall the pulley and often times wont allow you to get it as tight as it needs to be. Also, when your pulley is loose for a while it can deform the key and even the keyway making a less than optimal fit. This slop will tend to work the pulley loose after you have tightened it. The best thing to try first is to get a new set screw and either get a new key or flip your current key over (if its not a half moon). As the other reply stated, keys and set screws are cheap, changing them wouldnt cost more than a dollar or two. If you can get a knurled cup set screw they are the best as they actually bite into the key.

I wouldnt put any locktite on the shaft/pulley connection but you could use some removable loctite on the set screw. I would however try to fix the problem without it as you may have a tough time getting the set screw broke loose after you locktite it in. A better option would be to get a slightly longer set screw than the one you have (perhaps

1/4-3/8 longer) and getting a jam nut. Lock down your set screw then lock the jam nut against the body of the pulley. This would stop the set screw from backing out. Just make sure you dont get a set screw too long because often times a socket head set screw (allen) will crack if the socket is not supported in a tapping.

We have a contractors saw that we use on jobs and it has a pulley that comes loose like this on occasion.

Mark

[spaco]

Since you say that the pulley comes loose VERY easily, and that it's "way past that now":

Sounds like the pulley has worn itself loose on the shaft. I wonder if the "blue stuff" is what someone else used to try to fill the gap????? Would it be possible to get a new pulley? I'm assuming that the pulley is made of softer stuff than the shaft. To check this, you need to measure the shaft diameter to see if it has worn more in one spot than in some non-used portion. Pulley looseness of more than about 0.002" can cause the problem you have. That's why "the book" shows the pulley being "hammered" onto the shaft. It should fit snuggly.

There are other ways to address this issue, but they require some machining and accurate meeasuring skills and tools.

If you want some thoughts, email me off list.

Pete Stanaitis

Owen Lawrence wrote:

[Father Haskell]

Blue Loctite. It'll hold, but won't be too hard to break if you have to.

If that fails, drill out and tap the arbor sheave setscrew one size larger.

Both sheaves need to be coplanar -- check with a straight edge. Both need to be secured to straight shaft, not shoulders or ends. Is the motor frame centered on the bracket?

[LRod]

Remove the set screw. Then tighten the set screw that's still in there. Finally, reinstall and retighten the set screw you removed.

Double set screws have been known to have been applied in several instances. Tightening the one on top gives you the impression you are accomplishing something but in actuality, you're simply tightening it against the bottom one which isn't changing at all.

[DonkeyHody]

As others have said, spring for a couple of new pulleys. Get the ones that are machined instead of cast. It will smooth out your vibration as well as staying on the shaft. A little Locktite on a setscrew of your new pulleys should prevent them from backing out. Locktite comes in several grades. You want the one that allows you to loosen the bolt later.

DonkeyHody "There's a difference between doing things right, and doing the right things."

[beecrofter]

A machined pulley will be an improvement over the cast ones usually found on these saws, but for now to get you by - try using a second set screw behind the first one to lock things in place. Odds are that your clicking noise is the motor start mechanism, quite a normal sound but now your ears are out looking for trouble.

[Owen Lawrence]

Thanks for all the replies so far. I called Busy Bee Tools, the vendor of my saw, and they said that the blue colouring on the end of the shaft was machinist's bluing (not an adhesive). He recommended Loctite, and a new key, setscrew, or pulley if it's too loose. I haven't had a moment to myself since I posted my questions so I can't tell you yet how the problem was (rather, will be) solved.

For the record, my pulley IS a machined steel pulley. There is a single setscrew, and it doesn't seem to be sloppy. It bites into the key, but I'm considering replacing it. (Trips to the store are costly, even if what I buy isn't.) They key may be worn a bit; I have another length of it in my toolbox so I'll probably just replace it while I'm at it. A new pulley is only $10, so if it does fit better I'd say it's worth it. I can always use the old one in some other project.

I will not leave the guard off. End of that discussion.

Phil, I'd like to hear more about that screen door turnbuckle alignment tool. Do you have any pictures or diagrams of it?

- Owen -