A backing pad is a surface that the hook and loop material used for attachment on your sander or polisher. The backing pads that you purchase depend on what you are using the tool for; there are different sizes, shapes and textured surfaces to help with specific jobs. A 75 mm backing pad or a 150mm backing pad is a good size for sanding small parts and corners. A 250mm is great for large surfaces and flat sanding, and the 280mm and 320mm backing pads are popular with hobbyists due to their larger surface area.
The backing pad on your sander attaches to the rotary tool via hook and loop fasteners, which allow you to attach different types of attachments such as pads or brushes without having to drill holes in each one. It also helps keep the machine running smoothly by giving it extra weight; this spreads out the vibrations that can be felt when using a low-power machine.
Some tools may come with an attached rubberized machined surface that can be peeled off and replaced by either pressure-sensitive discs or other available attachments such as polishers.
In most cases, a backing pad is flat and made of plastic or metal that may contain holes for attaching pressure-sensitive adhesive products or others such as an adapter to allow the use of standard accessories.
Random Orbital Sanders
The most common size for a backing pad is 3 inches by 9 inches in diameter, which accommodates a majority of the available attachments on the market. You can also find smaller pads with different shapes and sizes so you can fit them to your specific sander or polisher model. Sanding sponges are usually used with handheld random orbital sanders because they have Velcro adhesive backs that allow them to easily attach to the backing pad.
Backing Pads and Sanding Discs
Pressure-sensitive adhesive discs are commonly used with orbital sanders and there is a specific backing pad that allows its users so they can be attached without any problem or movement during operation. Each type of attachment has different types of materials, sizes, shapes, Velcro hook & loop adhesion strength or torque needed for attaching them to your tool's backing pad.
To determine what size backings pads you need look at the label on the bottom of your sander/polisher where it reads "attachments", this will give you the diameter measurement of the required backing pad. If you don't see a label then refer to an old catalogue or manual that came with your sander/polisher.