How to Put a Sanding Disc on a Sander

What you need before you start

Most sanders that take round discs use a hook and loop pad. The pad has tiny hooks, and the disc has a fuzzy backing that grips them. Swapping a disc takes about a minute once you know the routine.

Before you begin, check three things. If any of them is off, the disc will not sit right.

• Disc size: it should match your pad diameter. Most random orbital sanders take 5 inch discs, as our best sanding discs page explains.
• Backing type: the disc must be hook and loop if your pad is hook and loop.
• Hole pattern: a punched disc, such as an 8-hole disc, should match the holes in your pad. Mesh discs do not need to match.

Step by step: attaching the disc

Follow these steps in order. They apply to most random orbital and similar round pad sanders.

• Switch the sander off and unplug it. For a cordless model, remove the battery.
• Set the sander on its back or hold it with the pad facing up so you can see the pad clearly.
• Brush or wipe dust and debris off the pad. Dust and bits of old abrasive are the main reason discs lose their grip.
• Peel off the old disc, if there is one. Pull from one edge in a steady motion.
• Hold the new disc with the abrasive side facing you and the backing side toward the pad.
• Line up the dust holes with the holes in the pad. Turn the disc slowly until you can see through every hole.
• Press the disc flat onto the pad. Start at the center and work outward with your palm so no edge is left raised.
• Give the disc a light tug. It should resist, not slide.
• Check that the disc sits centered and does not hang far over the edge of the pad.

Which side of the sanding disc is the right one

The abrasive side is the one you always use for sanding. It is the gritty face. The other side is the backing. On a hook and loop disc it feels soft and fuzzy, and it is the side that presses onto the pad.

If you are unsure, run a finger across both faces. The rough, gritty one is the working side. The soft, fuzzy one goes against the sander.

Some discs print the grit number on the back. Our list of picks includes a small 5-inch starter pack and a wet and dry silicon carbide set with grit printed on the back. That printing is handy when you pull loose discs out of a mixed pack and need to know which grit you are holding. It also confirms which side is the backing.

Lining up dust holes and mesh discs

Dust holes pull sanding dust through the disc and into your sander's extraction. If the holes sit over solid pad, the dust has nowhere to go. It packs into the abrasive and clogs the disc sooner.

Mesh or net discs work differently. The Dura-Gold ceramic mesh discs in our data are described as not needing to line up with the backing plate's hole pattern. That makes them easier to place. Small discs for rotary tools use a different setup, so the table below sums up the differences.

Mistakes that make discs slip or wear out early

Most problems come from the pad or from rushing the swap. A few habits prevent nearly all of them.

Do not skip cleaning the pad. Trapped dust blocks the hooks. Do not press only one side of the disc, because a raised edge can catch and peel off while the sander runs.

Watch for a worn pad too. If the hooks are flattened, new discs will not hold well, and the pad itself needs replacing. Some makers also sell a pad saver or hook saver that adds grip, and 3M suggests one for its net discs.

Match the disc to the tool. A 5 inch disc on a smaller pad will hang over the edge. A disc that does not match your pad will not hold or extract dust, so always check size first.

For small jobs on a rotary tool, the Rvetol kit in our data includes backing pads with 1/8 inch and 1/4 inch shanks. Pick the one that fits your tool's chuck, then press the 2 inch disc on the same way.

Safety checks before you sand

Always disconnect power before you touch the pad or disc. A sander that starts by accident while your fingers are near the pad can cause a cut or a serious injury.

Wear eye protection, since stray grit and debris can fly off a spinning disc. Wear a dust mask or respirator rated for fine dust, because sanding dust is unhealthy to breathe, especially from paint or treated wood. Wear hearing protection if your sander is loud.

Never sand old paint without checking for lead first, and use extraction where you can. Let the sander reach full speed before it touches the surface, and lift it off before you switch it off.

One more note: some products, like the 3M net discs in our data, are listed for industrial or occupational use only. Check the maker's labeling before you buy.

Picking the right disc for the job

Once you know how to attach a disc, choosing the right one gets easier. Low grits such as 40 and 60 remove material fast. Grits from 120 to 240 smooth. Grits of 400 and up prepare for finish.

If you are sanding a large surface such as a deck, the sander matters as much as the disc. Our best sander for sanding a deck page compares options for that kind of work. Then use the best sanding discs page to match grits and pack counts to your tool.

Frequently asked questions

How do I know when to change a sanding disc?

Change it when the abrasive looks smooth or clogged, when sanding slows down, or when the edges tear. A fresh disc cuts faster and puts less strain on the sander.

Can I reuse a disc after taking it off?

Sometimes. If the abrasive is still sharp and the backing is still fuzzy, it can go back on. Brush it clean first and expect the grip to weaken each time.

Why does my disc keep coming off?

Usually the pad is dirty or worn, the disc is the wrong size, or the backing is not hook and loop. Clean the pad, press the disc on firmly, and check that the size matches.

Do I need to turn the sander on to seat the disc?

No. Never run the sander to seat a disc. Press it on by hand with the power off.

Can I switch grits mid-job?

Yes. Work up through the grits in order, for example from a coarse grit to a finer one, and swap discs each time so coarse grit does not linger on the pad.