Guido,
I am not farmiliar with the PC 5" orbital sander, but because you said you bought it "used" sends up flags. You should not be able to stop a spinning disk with your hand, unless you have a very very large and strong hand with big callouses. Does this sander have a select speed switch somewhere? If not, you may have to bring it to a PC repair shop for some work. Not too bad if you bought it at a low price. Sorry I could not be of more help. A side note---check the brushes.
Joe Z.

 

Guido, to me this sounds like normal operation. If you press hard enough, yes the spinning action of the pad can be stopped, but the elliptical motion should not. This simply means you are pressing too hard. Like any sander, you should pretty much let the weight of the tool do the work, and only apply light pressure at the most.

1/16-1/8" of material removal is a lot to ask of a 5" ROS. Yes, it will do it if you sand long enough, but this is not its intended purpose. It is meant to smooth out imperfections on a surface.

For better material removal first use a plane, or planer, and then sand.

You did mention the sandpaper was new, but 5 minutes of use is likely beyond the useful life of the paper. Always change to fresh sandpaper when it's cutting action decreases, as the performance will be drastically affected.

Many 6" ROS's will take material off way faster than most 5" models, though I much prefer the one handed use that the 5" offers.

 

Jim is dead on with his post! it sounds like a normal ros to me.

 

Thanks Jim, you offer many good tips in your post. One thing I didn't know is the paper would last so short of time (I planned on sanding an entire picnic table with this... may have to rethink that now). I thought 1/16" was nothing for this thing... time to sharpen the ol' hand plane.

 

Well Guido.. That much thickness is a job for a plane or a belt sander. I've got an old Cr*psman 4"x21" BS and some 18 grit belts I use for "power planing". Also, if you're trying to hog off material like that, 120 grit is way too fine, IMO. If you decide to use the ROS 'd recommend picking up a box or 60, or even 40 grit to take off the bulk, then move to finer grit.

 

sounds to me like a normal ros sander to me as well.. 1/16th -1/8th " is a job for a good belt sander, then you go with your ros and start with 120g and work up to 220 or finer and finish with a good block sander with 220 to get the swirl marks out left by the ros

 

Guido, is this an electric or air sander? If this is an air tool a few drops of Marvel Air Tool Oil in the tool before you start will amaze you. Next, is the sander locked for circular sanding or set for random orbit? Heavy sanding requires the circular setting. To remove that much material I would start with a 36 grit and progress to 50, 80, 120, 180 and then switch to random orbit with 220. As others have mentioned you would get quicker results with a belt sander on a large project like a picnic table.
Now the big money saving tip: with any sand paper you can extend the life by cleaning it with a sanding belt cleaner. These come as sticks about 1-1/2 x 1-1/2 x 8" and sell for $5.99 at HF. When your belt, disk or paper loads up a few quick swipes and it is clean and like new. These sticks are similar to an art gum eraser. You can extend your papers life by about 5 times making this a real time saver and great value. You can also buy them from PC dealers at a higher price.

 

I have a 6" RO sander and i can't stop it I can push down hard and it will slow down but not stop I belive i would take to a repair shop Or call and ask the pro repair And see their answare ?

 

I found this on the Porter Cable website:



Pad rotation speed on a Porter-Cable random-orbit sander will normally vary from zero to a few hundred rpm (in either direction), depending upon existing conditions. These variations provide the random sanding action that is very desirable in wood finishing operations.

The sanding pad rotation is free-floating. The sander motor has no direct connection to make the sanding pad spin. The sander motor turns a counter-weight (eccentric housing), to which the sanding pad is attached through a ball bearing (or bearings on some models). That bearing is mounted off-center to the axis of the counter-weight.

As the motor rotates the counter-weight, the center of the sanding pad moves in a small circle around the axis of the counter-weight. The sanding pad is free to rotate on the ball-bearing, in reaction to friction created between the pad and the work piece. Some models also include a pad brake feature to limit maximum pad speed. This brake consists of an o-ring that provides resistance to pad rotation.

The speed and direction of pad rotation will vary depending on the amount and specific location of the friction created. Several factors affect friction and resulting pad rotation, such as: sandpaper grit & condition, the hardness of the work piece, the angle and amount of applied pressure.