Question about Bosch 3725DEVS ROS repair

[Wayne Jolly]

Some time ago I asked how hot your ROS gets because my Bosch would get so hot that there were parts that you didn't want to touch. Recently, I took it over to my daughter's house to work on a couple of things, and the first time I turned it on, the sanding pad flew across the garage. A part called the "carrier", or "Driver" snapped. So I finally got around to ordering new bearings, etc. for it, and of course the new driver. I have taken it all apart, cleaned it up, and installed the new parts. Assembly was simple enough as there is only one way it all fits together again. I have used it a couple of times now and it no longer gets anywhere near as hot as it used to, and it is smoother too. But! IT BLOWS! After a sanding session with it, there is sanding dust everywhere.

I disassembled it again yesterday, and there is dust all over inside it. There is more dust inside it after an hour or two of use than after all of the years of using it before I disassembled it the first time. There is even a lot of dust in the motor up in the brushes area. It's almost like the thing has decided to run backwards or something. The dust cannister does get dust in it, and it will fill up. But if I "dry run" the sander with no cannister on it, there is a little air coming out the dust port, but there is more air coming out of the ring called . . . well . . . it is unnamed in the parts list. The user guide calls it a "damper ring".

If you have any experience or comments about why this might be happening, I'm all . . . eyes. :-)

Thanks,

Wayne

P.S. In the parts diagram there is a part called "Contact Strap". I'd also be curious what it's purpose is since it doesn't actually contact anything.

[Jim Andrew]

When my Bosch ros breaks, plan to send it to a service center to be rebuilt, as your experience pretty much fits my pattern. I was successful repairing my Hitachi finish nailer.

[Dave Gellis]

Hi Wayne,

I tried sending a PM to you, but I"m not sure it went through.

I have to replace my "driver" (3-boss coupling) on my 3725DVS, but I'm unable to remove the driver. From the parts drawing, it appears to have two bearings pressed on it's hub, and the OD of the bearings fits into either the fan housing or the suction hood. The drawing only shows one view, so I can't tell. I've tried pressing against the underside of the driver, but it doesn't budge. Do you have any suggestions on how to remove the driver?

Thanks,

Dave

[Bryan Cowing]

I have popped the drive bearing out by using air pressure. Rubber tipped blowgun inserted into centre of bearing hole. Dust seems to clog the bearing when using vac hose on the sander.

[Wayne Jolly]

Dave - I don't remember anything being pressed together so tightly that I couldn't get it apart (and back together) by hand with the exception of the broken piece of the driver, and since I had new bearings anyway . . . In our PMs I mentioned making a drift to re-install the bearings, but I think that might have been another project. I had that sander together and apart a few times trying to find out why it seemed to be running backwards. Almost everything would only go together one way (I even tried to put it together wrong a time or two), and press fit parts were able to be pressed by hand. In our PMs you mentioned the plastic fan, and yeah, that was scary getting that off, but it unscrews if I remember right. I don't remember if it was right or left handed threads. Sorry that I cannot be more helpful.

Wayne

EDIT: Thinking about this a little more, I don't think I took the fan off at all.