MIMF

I have a PC 333 Random Orbit Sander, and I think it's broke. I've had this unit for about 8-9 years, with not a whole lot of use, mostly household projects and such. When the pad is picked up from the work, it starts to spin like the dickens, and won't go back to its usual random orbit until you press it back into the work. Even if pressure is let up from the pad, like if you're attempting edges, it starts to spin and you get that twisting/pitching of holding a rapidly spinning tool and makes it difficult to control.

This is wrong, right? I'm pretty sure it didn't do this when I got it. Actually, it's the first and only ROS I've ever used, as I grew up with one of those tan-colored, rectangle-padded Craftsman jobbies.

From looking at the exploded diagram in the manual, there is some sort of belt that attaches to a cam or something that creates the wobble. Is this something that can be fixed by tearing it open, cleaning dust out of an area, maybe replacing a part, or do I need to head over to that ROS discussion and pick up tips on a new unit?

By the way: Chuck, if you're reading, I ran into this problem while actually WORKING ON A GUITAR!

If the little belt hasn't broken, a good cleaning might make it operate properly again. I believe the belt is what makes the pad slow down when the sander is removed from the work. If too much crud has built up between the pad and the motor the pad might not be disengaging from the motor. My PC 333 has egged out the screw holes that hold the pad in place. The screws worked loose and destroyed a new pad in just a couple of minutes. I haven't decided if I should try tapping the holes for larger screws or just junk the sander. The PC343 is on sale for $39- $49 at various places.

pitch it before you hurt yourself (g).
Oh, and both Chuck and I are speechless. Can't wait to see it...at least not very long, I'm already 60 you know.

I will pull the little beasty apart and take a look at the belt. If things look iffy, then I'll head to the Depot for a full replacement. This thing isn't exactly easy on the hands if you have to use it for any more than a few minutes, and I did see some good recommendations on that other thread.

I hear ya! I'm just happy to get some time in the shop and make progress, Randy. I'm still running into the issue of having to build tools as I go: the work I did on the guitar was in addition to building a router table and a vacuum hold-down.

Nice! Best to break tools while working on guitars. The tool is assured a place in tool-Valhalla. If it broke while just - I dunno - making a bracket to hold a vacuum pump, then it is stuck in tool-limbo till you finish a guitar.
Which isn't too bad for a ROS since they generally do very well at the Limbo.

Gosh, I didn't realize you were a religious man, Chuck!

As the illustrious MC Hammer would say: "Can't Touch This"

I shall not!

Tore open that bugger after work this afternoon. Cleaned out a lot of VERY fine dust from the fins, which was probably a good thing for it. I also noticed that the little belt that holds onto the eccentric cam thingy was a little loose. It was letting the pad spin too freely. I just gave it a figure-8 twist and now it's fine. Of course, that belt will probably wear out sooner or later, because it's actually a friction action that regulates the rotation of the pad, not a pulley sort of setup. Still going to take a look at the ROS selection next time I'm at the Depot.

Thanks, folks! Case closed!

If you can stand the noise, and have a good sized compressor, a pneumatic ROS is fantastic! Its so easy to swing over curves because there is very little rotational mass like an electric. The difference is night and day. Though I've played with a pneumatic, I only own an electric.

Yeah, I saw David King's recommendation over in that ROS thread. I have a compressor, and I'd use it infrequently enough that I wouldn't mind the noise. When I eventually replace this PC, I'll include a pneumatic unit in my considerations.

The urethane belts for the PC 343 aren't too expensive. Item number 903373, $2.49 ea (with $9 shipping)

Air sanders use a lot of air. Unless you have a large compressor I wouldn't recommend them. The good ones do work well, but are not especially cheap.
The Despot was sold out of the PC343 sanders, so on impulse I bought a cheapie Ryobi ROS.

Clay is right about the gobs of air the disc air sanders need. The one exception is the Dynabrade Model-T which I've waxed on about several times.

I see that my rant about parts, shipping, and specific suppliers was removed. My bad.

The Mirka Ceros has many of the advantages of the professional air sanders, but it runs on 22V DC via a transformer. I got one mainly for sanding finishes, which it does really well, but it does a good job with coarser grits on wood, too. I use the ABRANET abrasive discs with it, which is aluminum oxide bonded to a fabric mesh, and hook the unit up to my Nilfisk shopvac, and I can sand essentially dust free. My lungs and shoulders send their thanks...