How to choose a random orbital sander: disc and power supply

To sand wood, filler, paint and metal with a single tool, the most versatile choice is the random orbital sander with a 125 mm disc: it removes stock and finishes without leaving scratches in a single direction. With a cordless one (12 or 18 V) you work without a cable on site, with a corded one (230 V) you have continuous power in the workshop, with the air model all you need is a compressor. In the collection, weights range from under 1 kg to about 2.9 kg and the speed reaches 24,000-26,000 orbits per minute.

Types

• Random orbital sander (or random-orbit sander): the backing pad rotates and oscillates at the same time. It removes material quickly and leaves a uniform finish. It is the most common type and comes with 125, 150 and 180 mm discs.
• Orbital sander: in the classic version the backing pad oscillates without rotating. It is used for finishing, where the finish matters more than the amount of material removed.
• Palm sander: compact, held in one hand. Good for tight spaces, edges and touch-ups.
• Pneumatic sander: it runs on compressed air. It has no electric motor and stays light, but it requires an adequate compressor.
• Compact cordless sander: the 12 V series have small discs for detail work, such as the 75 mm random orbital sander M12 FUEL Milwaukee. The 18 V series, such as the 125 mm random orbital sander M18 FUEL, have the full 125 mm disc.
• Random orbital and rotary polisher: it is not for sanding. A pad is fitted and it is used to polish paintwork and surfaces that have already been sanded.

How to choose by job

Features to look at

• Disc diameter (125, 150 or 180 mm): 125 is the most versatile. 150 covers more surface and is suited to large panels and walls. A larger disc, however, weighs more in the hand. Discs and backing pad must have the same diameter and the same holes.
• Orbits or revolutions per minute: values range between 6,000 and 26,000 orbits per minute. The high value is for roughing, the low one for delicate paintwork, plastic and polishing.
• Speed adjustment: the collection offers from 4 to 8 levels. If you work on different materials, choose an adjustable model.
• Voltage (12, 18, 20 V cordless; 230 or 240 V corded): it determines run time and power. Do not compare watts between cordless and corded, because the values are not equivalent.
• Power (from 135 to 1,300 W): it tells you how robust the motor is. On corded models, look for the higher value if you rough out often.
• Weight (from 0.93 to 2.9 kg): if you sand overhead or for hours, every bit of weight counts.
• Sound power (from about 85 to 93 dB(A)): at the end of the day you can feel the difference. Wear ear defenders anyway.
• Dust extraction: check that the backing pad has holes and that it connects to a vacuum cleaner or a dust bag.

Common mistakes

• Pressing down on the machine: it overheats, the disc wears quickly and the surface gets marked. Let the weight of the tool do the work.
• Skipping grits: starting with a fine grit on a rough surface never gets you finished. Proceed from the coarsest to the finest, without skipping too many.
• Buying on watts alone: disc, weight, adjustment and dust extraction matter too.
• Not checking the battery: before ordering, check on the data sheet whether the battery and charger are included or have to be bought separately.
• Working without dust extraction and a mask: fine wood and paint dust is harmful. Connect the vacuum cleaner and wear a dust mask.

Frequently asked questions

What is the difference between an orbital and a random orbital sander?

In the orbital sander the backing pad only oscillates; in the random orbital sander it oscillates and rotates at the same time. The random orbital sander removes more material and leaves fewer marks, which is why it is the most widely used.

Can I sand metal too?

Yes, with the suitable abrasive disc, to clean and flatten. For paints, start with a medium grit and finish with finer grits.

Cordless or corded?

Cordless is handy on site and at height. Corded is the choice for long, repeated jobs, in the workshop or on the shop floor.

How many speeds do I need?

If you work on a single material, a few are enough. If you move from wood to paint or plastic, choose a model with more speed levels.

You will find all the models in the random orbital sanders collection: if you are not sure which one to choose for your job, request a quote or advice from the AMES technicians.