Sanding discs are efficient. They can make any orbital sander run like new if they stick properly. Most often they work perfectly and will last for hours. But orbital sanders revolve at high speed, and if a sanding pad isn't extremely sticky, it can fly off. Don't throw it out -- you can keep using it.
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How They Work
Orbital sanders use round sanding discs that are held in place with glue, like a bumper sticker. They have a plastic-coated piece of paper stuck to the back. When you pull the paper off, it exposes a sticky surface. The pad is then placed on the orbital sander pad so the sticky surface adheres to the orbital pad. Typically the pads stay in place until the grit wears off the pad. The user then pulls the pad off and sticks on a new one.
Dust is the culprit when pads do not stick properly. Occasionally pads are removed before they are worn out because a different grit of sandpaper is needed. This can render the sticky surface of the removed pad obsolete. Other problems arise if the pad is dropped. When dust gets on the pad, it loses its grip and will not stick. Occasionally a pad will come loose on one side and dust will work its way under the pad, causing it to come loose.
Don't throw the pad away if it loses its grip. Start by wiping the loose debris and dust from the pad with your fingers and a dry cloth. Dampen a cloth with acetone and wipe it until it's smooth and clean. Also wipe off the orbital sanding pad lightly with acetone, making sure it's also clean. Lay the clean pad upside down on a work table and spray a light coat of aerosol glue on the pad. Let it dry for one minute. Position the sander directly above the pad and then place it squarely in the center of the pad, using the weight of the sander to adhere the pad to the orbital sander base.
If you are using bulk sanding discs, don't spend a lot of time trying to reuse them when they get dirty. It's counterproductive to spend time on them unless you have only a few and don't use them often. If you buy them by bulk, you can get them far cheaper. If one gets dirty, just replace it. You can reuse the dirty one on a sanding block; just staple it to any wooden block.