Can I get some help fixing my random orbital sander?

[Zach England]

I have a porter cable 333 variable speed random orbital sander. One day it smoked and quit being "random". I took the pad off to find the belt broken and the plastic around the screw and bearing you see in the left of the below picture was melted. I ordered a new belt and plastic base, but something is not quite right The screw in the bearing that holds the pulley belt is reverse-drive, but it either is too tight to let the bearing spin or it is loose enough to allow slop that also results in the bearing not spinning. Either way, the belt is pulled along the bearing and creates friction, which was presumably the caue of the previous failure. When I turn it on at low speed it neither spins nor moves the belt at all, and at higher speeds it will spin and move the belt, but not the bearing, obviously resulting in the same heat generation. if I remove the belt the center arbor continues to spin, but is not pulled to make it "random". I checked the parts diagram again and again and I don't see that I can be missing anything, but am not sure how the bearing and belt are supposed to behave. Can someone please advise? Thanks so much and sorry for the rambling.http://i121.photobucket.com/albums/o237/zachslc/IMG_0277.jpg

[David Christopher]

Zach, put a couple drops of PB Blaster on the bearing and let it sit upside down for a little while and it should be fine......mine done the same thing

[Zach England]

Thanks. Can I substitute wd-40? Are you talking about the bearing with the reverse-thread screw?

[David Christopher]

Zach, you can use WD 40 but PB Blaster is 100 times better for these kinds of things.....yes the little bearing in the middle

[Zach England]

Thanks. I will try it tonight with the wd40 and try to get some better lubricant tomorrow.

[David Kreuzberg]

Probably wouldn't hurt to replace both bearings, as they are both the same age and in a dusty environment, and probably not the best grade to start with.

Bearings are cheap, and these are easy to access.

kreuzie

[Steve Clardy]

Yep. I'd bet the bearing is froze up.

I've had 6-7 of those sanders over the years. Wore them all out.

[Zach England]

Ok, I replaced the small bearing that the pulley runs on. It works, but the bearing still gets very hot. I also got a replacement for the larger middle bearing, but I was not able to get the old one out because I could not budge the ring that holds it in. I got frustrated with it and just put it back together as is. I ran it on the lower speed for a little while to apply some wax to my table saw and it seemed ok, but sometimes makes a "screeching" sound that I believe is the belt rubbing on the smaller bearing. If it blows up again I will probably just buy a new sander, but I am hoping to give this one a bit more life because the variable speed models are pricey enough that they are worth a few minutes of my time to work on them. Do you think the heat is normal?

[Dave Sabo]

I just ran across this while overhauling mine.

It's my understanding that the small bearing is not really a bearing at all. In other words it's not supposed to move. Look at it closely and you'll see a groove in it that captures the belt . That's also why the revers threads instead of a smooth shaft for it to ride on.

So, no wd40 or grease ect..... on that one !

[Lee Schierer]

The white part is not a bearing it is a brake. It creates enough braking so that the random orbit feature works. It is not supposed to rotate. Do not add any lube as you will ruin the part and eliminate the random orbit action. The piece with the three screw holes in your photo is an eccentric and without the braking action it will spin at the motor rpm.

[Larry Edgerton]

Zack, I have about 30 of those things around here, and I am switching to Festool, so PM me your address and I will send you one, no charge.

Larry