Strange ROS behavior


My Bosch 5" ROS has recently become very hard to handle. I have had it for a few years now and have always found it to be quite easy to handle and yet powerful. However, lately I have barely been able to keep it on the work surface. I can see that it moves in both the circular as well as random motions still. I took the pad off to see what I could and found that there is a rubber ring that rides against the back of the sanding pad to direct the airflow for the dust collection through the proper ports. I found that the ring was caked with paint residue. Not thinking that this was relevant, I cleaned the residue off anyway before I put it back together. It was much more manageable, for a while. It went back to its difficult behavior fairly quickly. I took it apart again and found that the ring was again covered with paint residue, (BTW I was trying to sand out some primer). I cleaned it again and it ran better. I do not understand why the paint residue would cause it to behave the way that it does. Has anyone had the strange problem? I was thinking about putting a very light coat of silicone spray on the ring to see if that would prevent the paint from sticking to it. Does anyone have any better ideas?
SteveP.
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Highland Pairos wrote:

Me neither but I haven't seen an ROS disassenbled to see how they work normally.

Even the tiniest trace of silicon oil residue on wood will cause fisheyes in subsequent finishing attempts (except with shellac), or so Bob FLexnor says in _Understanding Wood Finishes_.
So it is probably a bad idea to use silicone lubricants on woodworking tools.
--

FF


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Silicone does not go away. I work in a high energy research lab, using epoxy and glass & graphite fibers. A test was done on silicone persistence. One year after introduction, (one event) it was EVERYWHERE!
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Got a female one eh?
> I took the pad off to see what I could and found that there

Some sanders have a wear part in them that control the orbital action. (My DeWalt even came with a spare) Perhaps something is worn enough not to direct the air properly, but enough that it is not at full capacity. Check the manual for references to something like that.
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If you're doing something like sanding off old finish you're probably much better off using a belt sander than an ROS to begin with. I've always considered the belt sander to be the work horse and the ROS to be for much finer surface work.
FoggyTown
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On Sat, 13 Aug 2005 00:21:06 GMT, "Highland Pairos"

Like Ed mentioned, I remember reading a tool review in one of the mags lately that talked about the brake pad wearing out. The brake pad acts as a "buffer" to keep the pad from starting right out on the random orbits to allow you to work your piece. If that is worn out it will act or orbit strange. You should look at your owners manual to see if the ring you mention is the brake pad and look to replace that.
Allyn
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Thanks folks. I know about the issues with silicone and that's why I didn't just try that solution without some input. Ed and Allyn thoughts about a wear component that effects the orbital actions makes sense. When I have it on the piece and under load it seems like it only spins and that there is no orbit to 'redirect' the motion. It might makes sense that a wearing or worn part would let it orbit with no load (which it does) but is too worn to do it under load.
Course now I have to try and find the manual.
SteveP.

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I have a Crapsman(Ryobi) ROS that occasionally starts vibrating & becoming "hard to handle". I discovered that the screw retaining the pad assy. bearing to the motor shaft had loosened slightly. After 2 or 3 occurrences, I tried some Loctite on the screw threads, it's been fine ever since. Seems this would fall in with the comments about worn parts. Just my $.25
--
Nahmie
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On Sat, 13 Aug 2005 15:13:40 GMT, "Highland Pairos"

Snip
From the Bosch web-site on sanders: http://www.boschtools.com/tools/tools-subcategory.htm?H 5979&GT925
Find you model and click on the link and it will give you a link to the owner's manual and part diagram. Not sure which one you have, but from the varibale speed manual:
"NOTE: If you notice steadily increasing no-load speed, this indicates that the damper ring is worn and needs to be replaced."
According to the manual, the damper ring is used to reduce no-load speed to prevent accidental marking of the workpiece...
Allyn
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I found my manual (amazing) and read the same thing. I already have a dampening ring on the way. We'll see how it works in 4-6 days.
SteveP.
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