Palm sander flys all over the place

[John Noell]

I have a little Makita BO4555 palm sander and (after loaning it out for a while) now when I try to sand something it wants to pull itself all over the place. I cannot hold it one place and sand anything. Everything looks okay (to my naive eye). If you hold it really tight and have someone hold the wood you are trying to sand it works, but it's a major hassle now. I recently replaced the armature and bearings (as it was returned with a bad armature) but don't see how that could have caused the problem. Any suggestions or insights?

[mreza Salav]

It is likely that the foam pad is loose or is damaged (separated).

[Gene Takae]

I'm not familiar with that particular sander but my PC 333vs has a little plastic belt that connects from the motor to a pulley under the pad. When the belt breaks the sander acts kind of funny. If yours has a similar design maybe it was not re-installed after the repair.

[Ed Edwards]

GO to http://www.ereplacementparts.com/makita-bo4556-14000opm-finishing-sander-parts-c-97_103_7544.html
and look at item #31. If it's anything like my PC 333 these are rubber mounts, after some use they get hard and my hand vibrates enough that I can hardly hang onto the sander. If these are really stiff, this might be your concern.
Ed

[Alan Rutherford]

The second time I took my new Makita sander in for repair the guy showed me how to hold it really firmly against something immoveable until the speed built up. There's so much mass in the pad relative to the motor that it loses a lot of energy vibrating the motor and doesn't have enough to push the speed up to where it smoothes out. That was a long time ago. I still have it. Don't use it a lot but when I do I hold the body down horizontal on the bench with both hands and let the pad spin in the air until it's OK - which takes a long time sometines.

[Prashun Patel]

I have issues sometimes with my ROS doing the same thing. The culprit was the washer between the pad and the motor spindle. I've had to replace mine once and it solved the problem.

On the parts diagram of your sander, it appears there is a 'balancer' and a ring bearing that might warrant inspection.

Of course, this may be the time to 86 your palm sander in favor of a ROS if you don't have one?

[John Noell]

Thanks everyone! I will start down the list and see what works. :)

[John Noell]

GO to http://www.ereplacementparts.com/makita-bo4556-14000opm-finishing-sander-parts-c-97_103_7544.html
and look at item #31. If it's anything like my PC 333 these are rubber mounts, after some use they get hard and my hand vibrates enough that I can hardly hang onto the sander. If these are really stiff, this might be your concern.
Ed On this model the "feet" (part 31) are solid aluminum with a very soft sponge foam cylinder around them. That doesn't seem to be the problem.
http://www.ereplacementparts.com/images/part_318151-8_med.gif

[John Noell]

I have issues sometimes with my ROS doing the same thing. The culprit was the washer between the pad and the motor spindle. I've had to replace mine once and it solved the problem.

On the parts diagram of your sander, it appears there is a 'balancer' and a ring bearing that might warrant inspection.

Of course, this may be the time to 86 your palm sander in favor of a ROS if you don't have one? The balancer is solid and looks intact. The bearing was just replaced and moves quite smoothly. I'd love to replace this little guy with an ROS, but the prices here are at least triple USA prices. I'd get one from the USA but we use 230V 50Hz here. (That said, I may yet get one and just run it on a trnsformer at 50Hz.)